Council Regulation (EC) No 440/2008 of 30 May 2008 laying down test methods pursuant to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) (Text with EEA relevance)

• (3)R. Weissberger edition: Technique of organic chemistry, Physical methods of organic chemistry, Third Edition, Interscience Publications, New York, 1959, vol. I, Part I, Chapter VIII.

Appendix

For additional technical details, the following standards may be consulted for example.

1. Ebulliometer

• 1.1.Melting temperature devices with liquid bath

ASTM D 1120-72	Standard test method for boiling point of engine anti-freezes

2. Distillation process (boiling range)

ISO/R 918	Test Method for Distillation (Distillation Yield and Distillation Range)
BS 4349/68	Method for determination of distillation of petroleum products
BS 4591/71	Method for the determination of distillation characteristics
DIN 53171	Losungsmittel für Anstrichstoffe, Bestimmung des Siedeverlaufes
NF T 20-608	Distillation: détermination du rendement et de l'intervalle de distillation

3. Differential thermal analysis and differential scanning calorimetry

ASTM E 537-76	Standard method for assessing the thermal stability of chemicals by methods of differential thermal analysis
ASTM E 473-85	Standard definitions of terms relating to thermal analysis
ASTM E 472-86	Standard practice for reporting thermoanalytical data
DIN 51005	Thermische Analyse, Begriffe

A.3.   RELATIVE DENSITY

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.4.   VAPOUR PRESSURE

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.5.   SURFACE TENSION

1. METHOD

The methods described are based on the OECD Test Guideline (1). The fundamental principles are given in reference (2).

1.1.   INTRODUCTION

The described methods are to be applied to the measurement of the surface tension of aqueous solutions.

It is useful to have preliminary information on the water solubility, the structure, the hydrolysis properties and the critical concentration for micelles formation of the substance before performing these tests.

The following methods are applicable to most chemical substances, without any restriction in respect to their degree of purity.

The measurement of the surface tension by the ring tensiometer method is restricted to aqueous solutions with a dynamic viscosity of less than approximately 200 mPa s.

1.2.   DEFINITIONS AND UNITS

The free surface enthalpy per unit of surface area is referred to as surface tension.

The surface tension is given as:

N/m (SI unit) or

mN/m (SI sub-unit)

1 N/m = 10³ dynes/cm

1 mN/m = 1 dyne/cm in the obsolete cgs system

1.3.   REFERENCE SUBSTANCES

Reference substances do not need to be employed in all cases when investigating a new substance. They should primarily serve to check the performance of the method from time to time and to allow comparison with results from other methods.

Reference substances which cover a wide range of surface tensions are given in references 1 and 3.

1.4.   PRINCIPLE OF THE METHODS

The methods are based on the measurement of the maximum force which is necessary to exert vertically, on a stirrup or a ring in contact with the surface of the liquid being examined placed in a measuring cup, in order to separate it from this surface, or on a plate, with an edge in contact with the surface, in order to draw up the film that has formed.

Substances which are soluble in water at least at a concentration of 1 mg/l are tested in aqueous solution at a single concentration.

1.5.   QUALITY CRITERIA

These methods are capable of greater precision than is likely to be required for environmental assessment.

1.6.   DESCRIPTION OF THE METHODS

A solution of the substance is prepared in distilled water. The concentration of this solution should be 90 % of the saturation solubility of the substance in water; when this concentration exceeds 1 g/l, a concentration of 1 g/l is used for testing. Substances with water solubility lower than 1 mg/l need not be tested.

1.6.1.   Plate method

See ISO 304 and NF T 73-060 (Surface active agents — determination of surface tension by drawing up liquid films).

1.6.2.   Stirrup method

See ISO 304 and NF T 73-060 (Surface active agents — determination of surface tension by drawing up liquid films).

1.6.3.   Ring method

See ISO 304 and NF T 73-060 (Surface active agents — determination of surface tension by drawing up liquid films).

1.6.4.   OECD harmonised ring method

1.6.4.1.   Apparatus

Commercially available tensiometers are adequate for this measurement. They consist of the following elements:

• — mobile sample table,

• — force measuring system,

• — measuring body (ring),

• — measurement vessel.

1.6.4.1.1.   Mobile sample table

The mobile sample table is used as a support for the temperature-controlled measurement vessel holding the liquid to be tested. Together with the force measuring system, it is mounted on a stand.

1.6.4.1.2.   Force measuring system

The force measuring system (see figure) is located above the sample table. The error of the force measurement shall not exceed ± 10^-6 N, corresponding to an error limit of ± 0,1  mg in a mass measurement. In most cases, the measuring scale of commercially available tensiometers is calibrated in mN/m so that the surface tension can be read directly in mN/m with an accuracy of 0,1 mN/m.

1.6.4.1.3.   Measuring body (ring)

The ring is usually made of a platinum-iridium wire of about 0,4  mm thickness and a mean circumference of 60 mm. The wire ring is suspended horizontally from a metal pin and a wire mounting bracket to establish the connection to the force measuring system (see figure).

Figure

Measuring body

(All dimensions expressed in millimetres)

Image omitted; see official source

Text of image

Mounting bracket

Pin

Ring

1.6.4.1.4.   Measurement vessel

The measurement vessel holding the test solution to be measured shall be a temperature-controlled glass vessel. It shall be designed so that during the measurement the temperature of the test solution liquid and the gas phase above its surface remains constant and that the sample cannot evaporate. Cylindrical glass vessels having an inside diameter of not less than 45 mm are acceptable.

1.6.4.2.   Preparation of the apparatus

1.6.4.2.1.   Cleaning

Glass vessels shall be cleaned carefully. If necessary they shall be washed with hot chromo-sulphuric acid and subsequently with syrupy phosphoric acid (83 to 98 % by weight of H3PO4), thoroughly rinsed in tap water and finally washed with double-distilled water until a neutral reaction is obtained and subsequently dried or rinsed with part of the sample liquid to be measured.

The ring shall first be rinsed thoroughly in water to remove any substances which are soluble in water, briefly immersed in chromo-sulphuric acid, washed in double-distilled water until a neutral reaction is obtained and finally heated briefly above a methanol flame.

Note:

Contamination by substances which are not dissolved or destroyed by chromo-sulphuric acid or phosphoric acid, such as silicones, shall be removed by means of a suitable organic solvent.

1.6.4.2.2.   Calibration of the apparatus

The validation of the apparatus consists of verifying the zero point and adjusting it so that the indication of the instrument allows reliable determination in mN/m.

Mounting:

The apparatus shall be levelled, for instance by means of a spirit level on the tensiometer base, by adjusting the levelling screws in the base.

Zero point adjustment:

After mounting the ring on the apparatus and prior to immersion in the liquid, the tensiometer indication shall be adjusted to zero and the ring checked for parallelism to the liquid surface. For this purpose, the liquid surface can be used as a mirror.

Calibrations:

The actual test calibration can be accomplished by means of either of two procedures:

• (a) Using a mass: procedure using riders of known mass between 0,1 and 1,0  g placed on the ring. The calibration factor, Φa by which all the instrument readings must be multiplied, shall be determined according to equation (1). Image omitted; see official source where: Image omitted; see official source m = mass of the rider (g) g = gravity acceleration (981 cm s^-2 at sea level) b = mean circumference of the ring (cm) σa = reading of the tensiometer after placing the rider on the ring (mN/m).

• (b) Using water: procedure using pure water whose surface tension at, for instance, 23 ^oC is equal to 72,3 mN/m. This procedure is accomplished faster than the weight calibration but there is always the danger that the surface tension of the water is falsified by traces of contamination by surfactants. The calibration factor, Φb by which all the instrument readings shall be multiplied, shall be determined in accordance with the equation (2): Image omitted; see official source where: σo = value cited in the literature for the surface tension of water (mN/m) σg = measured value of the surface tension of the water (mN/m) both at the same temperature.

1.6.4.3.   Preparation of samples

Aqueous solutions shall be prepared of the substances to be tested, using the required concentrations in water, and shall not contain any non-dissolved substances.

The solution must be maintained at a constant temperature (± 0,5 ^oC). Since the surface tension of a solution in the measurement vessel alters over a period of time, several measurements shall be made at various times and a curve plotted showing surface tension as a function of time. When no further change occurs, a state of equilibrium has been reached.

Dust and gaseous contamination by other substances interfere with the measurement. The work shall therefore be carried out under a protective cover.

1.6.5.   Test conditions

The measurement shall be made at approximately 20 ^oC and shall be controlled to within ± 0,5 ^oC.

1.6.6.   Performance of test

The solutions to be measured shall be transferred to the carefully cleaned measurement vessel, taking care to avoid foaming, and subsequently the measurement vessel shall be placed onto the table of the test apparatus. The table-top with measurement vessel shall be raised until the ring is immersed below the surface of the solution to be measured. Subsequently, the table-top shall be lowered gradually and evenly (at a rate of approximately 0,5  cm/min) to detach the ring from the surface until the maximum force has been reached. The liquid layer attached to the ring must not separate from the ring. After completing the measurements, the ring shall be immersed below the surface again and the measurements repeated until a constant surface tension value is reached. The time from transferring the solution to the measurement vessel shall be recorded for each determination. Readings shall be taken at the maximum force required to detach the ring from the liquid surface.

2. DATA

In order to calculate the surface tension, the value read in mN/m on the apparatus shall be first multiplied by the calibration factor Φa or Φb (depending on the calibration procedure used). This will yield a value which applies only approximately and therefore requires correction.

Harkins and Jordan (4) have empirically determined correction factors for surface-tension values measured by the ring method which are dependent on ring dimensions, the density of the liquid and its surface tension.

Since it is laborious to determine the correction factor for each individual measurement from the Harkins and Jordan tables, in order to calculate the surface tension for aqueous solutions the simplified procedure of reading the corrected surface-tension values directly from the table may be used. (Interpolation shall be used for readings ranging between the tabular values.)

Table:

Correction of the measured surface tension

Only for aqueous solutions, ρ = 1 g/cm³

r	= 9,55  mm (average ring radius)
r	= 0,185  mm (ring wire radius)
Experimental Value (mN/m)	Corrected Value (mN/m)
---	---
Experimental Value (mN/m)	Weight calibration (see 1.6.4.2.2(a))
20	16,9
22	18,7
24	20,6
26	22,4
28	24,3
30	26,2
32	28,1
34	29,9
36	31,8
38	33,7
40	35,6
42	37,6
44	39,5
46	41,4
48	43,4
50	45,3
52	47,3
54	49,3
56	51,2
58	53,2
60	55,2
62	57,2
64	59,2
66	61,2
68	63,2
70	65,2
72	67,2
74	69,2
76	71,2
78	73,2

This table has been compiled on the basis of the Harkins-Jordan correction. It is similar to that in the DIN Standard (DIN 53914) for water and aqueous solutions (density ρ = 1 g/cm³ and is for a commercially available ring having the dimensions R = 9,55  mm (mean ring radius) and r = 0,185  mm (ring wire radius). The table provides corrected values for surface-tension measurements taken after calibration with weights or calibration with water.

Alternatively, without the preceding calibration, the surface tension call can be calculated according to the following formula:

Image omitted; see official source

where:

F	=	the force measured on the dynamometer at the breakpoint of the film
---	---	---
R	=	the radius of the ring
---	---	---
f	=	the correction factor (1)

3. REPORTING

3.1.   TEST REPORT

The test report shall, if possible, include the following information:

• — method used,

• — type of water or solution used,

• — precise specification of the substance (identity and impurities),

• — measurement results: surface tension (reading) stating both the individual readings and their arithmetic mean as well as the corrected mean (taking into consideration the equipment factor and the correction table),

• — concentration of the solution,

• — test temperature,

• — age of solution used; in particular the time between preparation and measurement of the solution,

• — description of time dependence of surface tension after transferring the solution to the measurement vessel,

• — all information and remarks relevant for the interpretation of results have to be reported, especially with regard to impurities and physical state of the substance.

3.2.   INTERPRETATION OF RESULTS

Considering that distilled water has a surface tension of 72,75 mN/m at 20 ^oC, substances showing a surface tension lower than 60 mN/m under the conditions of this method should be regarded as being surface-active materials.

4. REFERENCES

• (1)OECD, Paris, 1981, Test Guideline 115, Decision of the Council C(81) 30 final.

• (2)R. Weissberger ed.: Technique of Organic Chemistry, Physical Methods of Organic Chemistry, 3rd ed., Interscience Publ., New York, 1959, vol. I, Part I, Chapter XIV.

• (3)Pure Appl. Chem., 1976, vol. 48, p. 511.

• (4)Harkins, W.D., Jordan, H.F., J. Amer. Chem. Soc., 1930, vol. 52, p. 1751.

A.6.   WATER SOLUBILITY

INTRODUCTION

• 1.This Test Method is equivalent to OECD Test Guideline (TG) 105 (1995). This Test Method is a revised version of the original TG 105 which was adopted in 1981. There is no difference of substance between the current version and that from 1981. Mainly the format has been changed. The revision was based on the EU Test Method ‘Water Solubility’ (¹).

INITIAL CONSIDERATIONS

• 2.The water solubility of a substance can be considerably affected by the presence of impurities. This Test Method addresses the determination of the solubility in water of essentially pure substances which are stable in water and not volatile. Before determining water solubility, it is useful to have some preliminary information on the test substance, like structural formula, vapour pressure, dissociation constant and hydrolysis as a function of pH.

• 3.Two methods, the column elution method and the flask method which cover respectively solubilities below and above 10^–2 g/l are described in this Test Method. A simple preliminary test is also described. It allows the determination of approximately the appropriate amount of sample to be used in the final test, as well as the time necessary to achieve saturation.

DEFINITIONS AND UNITS

• 4.The water solubility of a substance is the saturation mass concentration of the substance in water at a given temperature.

• 5.Water solubility is expressed in mass of solute per volume of solution. The SI unit is kg/m³ but g/l may also be used.

REFERENCE CHEMICALS

• 6.Reference chemicals do not need to be employed when investigating a test substance.

DESCRIPTION OF THE METHODS

Test conditions

• 7.The test is preferably run at 20 ± 0,5 °C. The chosen temperature should be kept constant in all relevant parts of the equipment.

Preliminary test

• 8.In a stepwise procedure, increasing volumes of water are added at room temperature to approximately 0,1 g of the sample (solid test substances must be pulverized) in a 10 ml glass-stoppered measuring cylinder. After each addition of an amount of water, the mixture is shaken for 10 minutes and is visually checked for any undissolved parts of the sample. If, after addition of 10 ml of water, the sample or parts of it remain undissolved, the experiment is continued in a 100 ml measuring cylinder. The approximate solubility is given in Table 1 below under that volume of water in which complete dissolution of the sample occurs. When the solubility is low, a long time may be required to dissolve a test substance and at least 24 hours should be allowed. If, after 24 hours, the test substance is still not dissolved, more time (up to 96 hours) should be allowed or further dilution should be attempted to ascertain whether the column elution method or flask method should be used.

Table 1

ml of water for 0,1 g soluble	0,1	0,5	1	2	10	100	> 100
approximate solubility in g/l	> 1 000	1 000 to 200	200 to 100	100 to 50	50 to 10	10 to 1	< 1

Column elution method

Principle

• 9.This method is based on the elution of a test substance with water from a micro-column which is charged with an inert support material, previously coated with an excess of the test substance (2). The water solubility is given by the mass concentration of the eluate when this has reached a plateau as a function of time.

Apparatus

• 10.The apparatus consists of a microcolumn (Figure 1), maintained at constant temperature. It is connected either to a recirculating pump (Figure 2) or to a levelling vessel (Figure 3). The microcolumn contains an inert support held in place by a small plug of glasswool which also serves to filter out particles. Possible materials which can be employed for the support are glass beads, diatomaceous earth, or other inert materials.

• 11.The microcolumn shown in Figure 1 is suitable for the set-up with recirculating pump. It has a head space providing for five bed volumes (discarded at the start of the experiment) and the volume of five samples (withdrawn for analysis during the experiment). Alternatively, the size can be reduced if water can be added to the system during the experiment to replace the initial five bed volumes removed with impurities. The column is connected with tubing made of an inert material to the recirculating pump, capable of delivering approximately 25 ml/h. The recirculating pump can be, for example, a peristaltic or membrane pump. Care must be taken that no contamination and/or adsorption occur with the tube material.

• 12.A schematic arrangement using a levelling vessel is shown in Figure 3. In this arrangement the microcolumn is fitted with a one way stopcock. The connection to the levelling vessel consists of a ground glass joint and tubing made of an inert material. The flow rate from the levelling vessel should be approximately 25 ml/h.

Figure 1

Image omitted; see official source

Dimensions in mm

• A.Connection for ground glass joint

• B.Headspace

• C.Interior 5

• D.Exterior 19

• E.Plug of glass wool

• F.Stopcock

Figure 2

Image omitted; see official source

• A.Atmospheric equilibration

• B.Flowmeter

• C.Microcolumn

• D.Thermostatically controlled circulating pump

• E.Recirculating pump

• F.Two-way valve for sampling

Figure 3

Image omitted; see official source

• A.Levelling vessel (e.g. 2,5 litres chemical flask)

• B.Column

• C.Fraction accumulator

• D.Thermostat

• E.Teflon tubing

• F.Ground glass joint

• G.Water line (between thermostat and column, inner diameter approximately 8 mm)

• 13.Approximately 600 mg of support material is transferred to a 50 ml round-bottom flask. A suitable amount of test substance is dissolved in a volatile solvent of analytical reagent quality and an appropriate amount of this solution is added to the support material. The solvent is completely evaporated, e.g. using a rotary evaporator, as otherwise water saturation of the support will not be achieved during the elution step because of partitioning on the surface. The loaded support material is soaked for two hours in approximately 5 ml of water and the suspension is poured into the microcolumn. Alternatively, dry loaded support material may be poured into the water-filled microcolumn and two hours are allowed for equilibrating.

• 14.The loading of the support material may cause problems, leading to erroneous results, e.g. when the test substance is deposited as an oil. These problems should be examined and the details reported.

Procedure using a recirculating pump

• 15.The flow through the column is started. It is recommended that a flow rate of approximately 25 ml/h, corresponding to 10 bed volumes per hour for the column described, be used. At least the first five bed volumes are discarded to remove water soluble impurities. Following this, the pump is allowed to run until equilibrium is established, as defined by five successive samples whose concentrations do not differ by more than ± 30 % in a random fashion. These samples should be separated from each other by time intervals corresponding to the passage of at least ten bed volumes. Depending on the analytical method used, it may be preferable to establish a concentration/time curve to show that equilibrium is reached.

Procedure using a levelling vessel

• 16.Successive eluate fractions should be collected and analysed by the chosen method. Fractions from the middle eluate range, where the concentrations are constant within ± 30 % in at least five consecutive fractions, are used to determine the solubility.

• 17.Double distilled water is the preferred eluent. Deionized water with a resistivity above 10 megohms/cm and total organic carbon content below 0,01 % can also be used.

• 18.Under both procedures, a second run is performed at half the flow rate of the first. If the results of the two runs are in agreement, the test is satisfactory. If the measured solubility is higher with the lower flow rate, then the halving of the flow rate must continue until two successive runs give the same solubility.

• 19.Under both procedures, the fractions should be checked for the presence of colloidal matter by examination of the Tyndall effect. The presence of particles invalidates the test and the test should be repeated after improvement of the filtering action of the column.

• 20.The pH of each sample should be measured, preferably by using special indicator strips.

Flask method

Principle

• 21.The test substance (solids must be pulverized) is dissolved in water at a temperature somewhat above the test temperature. When saturation is achieved, the mixture is cooled and kept at the test temperature. Alternatively, and if it is assured by appropriate sampling that the saturation equilibrium is reached, the measurement can be performed directly at the test temperature. Subsequently, the mass concentration of the test substance in the aqueous solution, which must not contain any undissolved particles, is determined by a suitable analytical method (3).

Apparatus

• 22.The following materials are needed:

• — normal laboratory glassware and instrumentation;

• — a device for the agitation of solutions under controlled constant temperature;

• — if required for emulsions, a centrifuge (preferably thermostated); and

• — analytical equipment.

Procedure

• 23.The quantity of test substance necessary to saturate the desired volume of water is estimated from the preliminary test. About five times that quantity is weighed into each of three glass vessels fitted with glass stoppers (e.g. centrifuge tubes, flasks). A volume of water, chosen in function of the analytical method and solubility range, is added to each vessel. The vessels are tightly stoppered and then agitated at 30 °C. A shaking or stirring device capable of operating at constant temperature should be used, e.g. magnetic stirring in a thermostated water bath. After one day, one of the vessels is equilibrated for 24 hours at the test temperature with occasional shaking. The contents of the vessel are then centrifuged at the test temperature and the concentration of the test substance in the clear aqueous phase is determined by a suitable analytical method. The other two flasks are treated similarly after initial equilibration at 30 °C for two and three days respectively. If the concentrations measured in at least the two last vessels do not differ by more than 15 %, the test is satisfactory. If the results from vessels 1, 2 and 3 show a tendency of increasing values, the whole test should be repeated using longer equilibration times.

• 24.The test can also be performed without pre-incubation at 30 °C. In order to estimate the rate of establishment of the saturation equilibrium, samples are taken until the stirring time no longer influences the concentrations measured.

• 25.The pH of each sample should be measured, preferably by using special indicator strips.

Analytical determinations

• 26.A substance-specific method is preferred since small amounts of soluble impurities can cause large errors in the measured solubility. Examples of such methods are: gas or liquid chromatography, titration, photometry, voltametry.

DATA AND REPORTING

Data

Column elution method

• 27.For each run, the mean value and standard deviation from at least five consecutive samples taken from the saturation plateau should be calculated. The mean values obtained from two tests with different flows should not differ by more than 30 %.

Flask method

• 28.The individual results from each of the three flasks, which should not differ by more than 15 %, are averaged.

Test Report

Column elution method

• 29.The test report must include the following information:

• — the results of the preliminary test

• — chemical identity and impurities (preliminary purification step, if any)

• — the concentrations, flow rates and pH for each sample

• — the means and standard deviations from at least five samples from the saturation plateau of each run

• — the average of at least two successive runs

• — the temperature of the water during the saturation process

• — the method of analysis

• — the nature of the support material

• — loading of the support material

• — solvent used

• — evidence of any chemical instability of the substance during the test

• — all information relevant for the interpretation of the results, in particular with regard to impurities and physical state of the test substance.

Flask method

• 30.The test report must include the following information:

• — the results of the preliminary test

• — chemical identity and impurities (preliminary purification step, if any)

• — the individual analytical determinations and the average where more than one value was determined for each flask

• — the pH of each sample

• — the average of the values for different flasks which were in agreement

• — the test temperature

• — the analytical method

• — evidence of any chemical instability of the substance during the test

• — all information relevant for the interpretation of the results, in particular with regard to impurities and physical state of the test substance.

LITERATURE:

• (1) Commission Directive 92/69/EEC of 31 July 1992 adapting to technical progress for the seventeenth time Council Directive 67/548/EEC on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (OJ L 383, 29.12.1992, p. 113).

• (2) NF T 20-045 (AFNOR) (September 1985). Chemical products for industrial use — Determination of water solubility of solids and liquids with low solubility — Column elution method.

• (3) NF T 20-046 (AFNOR) (September 1985). Chemical products for industrial use — Determination of water solubility of solids and liquids with high solubility — Flask method.

A.8.   PARTITION COEFFICIENT

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.9.   FLASH-POINT

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.10.   FLAMMABILITY (SOLIDS)

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.11.   FLAMMABILITY (GASES)

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.12.   FLAMMABILITY (CONTACT WITH WATER)

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.13.   PYROPHORIC PROPERTIES OF SOLIDS AND LIQUIDS

The full description of this test method has been deleted. The equivalent international test methods, or other applicable test methods for the endpoints in question, appear in Part 0, Table 1.

A.14.   EXPLOSIVE PROPERTIES

1. METHOD

1.1.   INTRODUCTION

The method provides a scheme of testing to determine whether a solid or a pasty substance presents a danger of explosion when submitted to the effect of a flame (thermal sensitivity), or to shock or friction (sensitivity to mechanical stimuli), and whether a liquid substance presents a danger of explosion when submitted to the effect of a flame or shock.

The method comprises three parts:

• (a) a test of thermal sensitivity (1);

• (b) a test of mechanical sensitivity with respect to shock (1);

• (c) a test of mechanical sensitivity with respect to friction (1).

The method yields data to assess the likelihood of initiating an explosion by means of certain common stimuli. The method is not intended to ascertain whether a substance is capable of exploding under any conditions.

The method is appropriate for determining whether a substance will present a danger of explosion (thermal and mechanical sensitivity) under the particular conditions specified in the directive. It is based on a number of types of apparatus which are widely used internationally (1) and which usually give meaningful results. It is recognised that the method is not definitive. Alternative apparatus to that specified may be used provided that it is internationally recognised and the results can be adequately correlated with those from the specified apparatus.

The tests need not be performed when available thermodynamic information (e.g. heat of formation, heat of decomposition) and/or absence of certain reactive groups (2) in the structural formula establishes beyond reasonable doubt that the substance is incapable of rapid decomposition with evolution of gases or release of heat (i.e. the material does not present any risk of explosion). A test of mechanical sensitivity with respect to friction is not required for liquids.

1.2.   DEFINITIONS AND UNITS

Explosive:

Substances which may explode under the effect of flame or which are sensitive to shock or friction in the specified apparatus (or are more mechanically sensitive than 1,3 -dinitrobenzene in alternative apparatus).

1.3.   REFERENCE SUBSTANCES

1,3-dinitrobenzene, technical crystalline product sieved to pass 0,5  mm, for the friction and shock methods.

Perhydro-1,3,5-trinitro-1,3,5-triazine (RDX, hexogen, cyclonite — CAS 121-82-4), recrystallised from aqueous cyclohexanone, wet-sieved through a 250 μm and retained on a 150 μm sieve and dried at 103 ± 2 ^oC (for four hours) for the second series of friction and shock tests.

1.4.   PRINCIPLE OF THE METHOD

Preliminary tests are necessary to establish safe conditions for the performance of the three tests of sensitivity.

1.4.1.   Safety-in-handling tests (3)

For safety reasons, before performing the main tests, very small samples (circa 10 mg) of the substance are subjected to heating without confinement in a gas flame, to shock in any convenient form of apparatus and to friction by the use of a mallet against an anvil or any form of friction machine. The objective is to ascertain if the substance is so sensitive and explosive that the prescribed sensitivity tests, particularly that of thermal sensitivity, should be performed with special precautions so as to avoid injury to the operator.

1.4.2.   Thermal sensitivity

The method involves heating the substance in a steel tube, closed by orifice plates with differing diameters of hole, to determine whether the substance is liable to explode under conditions of intense heat and defined confinement.

1.4.3.   Mechanical sensitivity (shock)

The method involves subjecting the substance to the shock from a specified mass dropped from a specified height.

1.4.4.   Mechanical sensitivity (friction)

The method involves subjecting solid or pasty substances to friction between standard surfaces under specified conditions of load and relative motion.

1.5.   QUALITY CRITERIA

Not stated.

1.6.   DESCRIPTION OF METHOD

1.6.1.   Thermal sensitivity (effect of a flame)

1.6.1.1.   Apparatus

The apparatus consists of a non-reusable steel tube with its re-usable closing device (figure 1), installed in a heating and protective device. Each tube is deep-drawn from sheet steel (see Appendix) and has an internal diameter of 24 mm, a length of 75 mm and wall thickness of 0,5  mm. The tubes are flanged at the open end to enable them to be closed by the orifice plate assembly. This consists of a pressure-resistant orifice plate, with a central hole, secured firmly to a tube using a two-part screw joint (nut and threaded collar). The nut and threaded collar are made from chromium-manganese steel (see Appendix) which is spark-free up to 800 ^oC. The orifice plates are 6 mm thick, made from heat-resistant steel (see Appendix), and are available with a range of diameters of opening.

1.6.1.2.   Test conditions

Normally the substance is tested as received although in certain cases, e.g. if pressed, cast or otherwise condensed, it may be necessary to test the substance after crushing.

For solids, the mass of material to be used in each test is determined using a two-stage dry run procedure. A tared tube is filled with 9 cm³ of substance and the substance tamped with 80 N force applied to the total cross-section of the tube. For reasons of safety or in cases where the physical form of the sample can be changed by compression other filling procedures may be used; e.g. if the substance is very friction sensitive then tamping is not appropriate. If the material is compressible then more is added and tamped until the tube is filled to 55 mm from the top. The total mass used to fill the tube to the 55 mm level is determined and two further increments, each tamped with 80 N force, are added. Material is then either added with tamping, or taken out, as required, to leave the tube filled to a level 15 mm from the top. A second dry run is performed, starting with a tamped quantity of a third of the total mass found in the first dry run. Two more of these increments are added with 80 N tamping and the level of the substance in the tube adjusted to 15 mm from the top by addition or subtraction of material as required. The amount of solid determined in the second dry run is used for each trial; filling being performed in three equal amounts, each compressed to 9 cm³ by whatever force is necessary. (This may be facilitated by the use of spacing rings).

Liquids and gels are loaded into the tube to a height of 60 mm taking particular care with gels to prevent the formation of voids. The threaded collar is slipped onto the tube from below, the appropriate orifice plate is inserted and the nut tightened after applying some molybdenum disulphide based lubricant. It is essential to check that none of the substance is trapped between the flange and the plate, or in the threads.

Heating is provided by propane taken from an industrial cylinder, fitted with a pressure regulator (60 to 70 mbar), through a meter and evenly distributed (as indicated by visual observation of the flames from the burners) by a manifold to four burners. The burners are located around the test chamber as shown in figure 1. The four burners have a combined consumption of about 3,2 litres of propane per minute. Alternative fuel gases and burners may be used but the heating rate must be as specified in figure 3. For all apparatus, the heating rate must be checked periodically using tubes filled with dibutyl phthalate as indicated in figure 3.

1.6.1.3.   Performance of the tests

Each test is performed until either the tube is fragmented or the tube has been heated for five minutes. A test resulting in the fragmentation of the tube into three or more pieces, which in some cases may be connected to each other by narrow strips of metal as illustrated in figure 2, is evaluated as giving an explosion. A test resulting in fewer fragments or no fragmentation is regarded as not giving an explosion.

A series of three tests with a 6,0  mm diameter orifice plate is first performed and, if no explosions are obtained, a second series of three tests is performed with a 2,0  mm diameter orifice plate. If an explosion occurs during either test series then no further tests are required.

1.6.1.4.   Evaluation

The test result is considered positive if an explosion occurs in either of the above series of tests.

1.6.2.   Mechanical sensitivity (shock)

1.6.2.1.   Apparatus (figure 4)

The essential parts of a typical fall hammer apparatus are a cast steel block with base, anvil, column, guides, drop weights, release device and a sample holder. The steel anvil 100 mm (diameter) × 70 mm (height) is screwed to the top of a steel block 230 mm (length) × 250 mm (width) × 200 mm (height) with a cast base 450 mm (length) × 450 mm (width) × 60 mm (height). A column, made from seamless drawn steel tube, is secured in a holder screwed on to the back of the steel block. Four screws anchor the apparatus to a solid concrete block 60 × 60 × 60 cm such that the guide rails are absolutely vertical and the drop weight falls freely. 5 and 10 kg weights, made from solid steel, are available for use. The striking head of each weight is of hardened steel, HRC 60 to 63, and has a minimum diameter of 25 mm.

The sample under test is enclosed in a shock device consisting of two coaxial solid steel cylinders, one above the other, in a hollow cylindrical steel guide ring. The solid steel cylinders should be of 10 (- 0,003 , - 0,005 ) mm diameter and 10 mm height and have polished surfaces, rounded edges (radius of curvature 0,5  mm) and a hardness of HRC 58 to 65. The hollow cylinder must have an external diameter of 16 mm, a polished bore of 10 (+ 0,005 , + 0,010 ) mm and a height of 13 mm. The shock device is assembled on an intermediate anvil (26 mm diameter and 26 mm height) made of steel and centred by a ring with perforations to allow escape of fumes.

1.6.2.2.   Test conditions

The sample volume should be 40 mm³, or a volume to suit any alternative apparatus. Solid substances should be tested in the dry state and prepared as follows:

• (a) powdered substances are sieved (sieve size 0,5  mm); all that has passed through the sieve is used for testing;

• (b) pressed, cast or otherwise condensed substances are broken into small pieces and sieved; the sieve fraction from 0,5 to 1 mm diameter is used for testing and should be representative of the original substance.

Substances normally supplied as pastes should be tested in the dry state where possible or, in any case, following removal of the maximum possible amount of diluent. Liquid substances are tested with a 1 mm gap between the upper and lower steel cylinders.

1.6.2.3.   Performance of the tests

A series of six tests are performed dropping the 10 kg mass from 0,40  m (40 J). If an explosion is obtained during the six tests at 40 J, a further series of six tests, dropping a 5 kg mass from 0,15  m (7,5  J), must be performed. In other apparatus, the sample is compared with the chosen reference substance using an established procedure (e.g. up-and-down technique etc.).

1.6.2.4.   Evaluation

The test result is considered positive if an explosion (bursting into flame and/or a report is equivalent to explosion) occurs at least once in any of the tests with the specified shock apparatus or the sample is more sensitive than 1,3-dinitrobenzene or RDX in an alternative shock test.

1.6.3.   Mechanical sensitivity (friction)

1.6.3.1.   Apparatus (figure 5)

The friction apparatus consists of a cast steel base plate on which is mounted the friction device. This consists of a fixed porcelain peg and moving porcelain plate. The porcelain plate is held in a carriage which runs in two guides. The carriage is connected to an electric motor via a connecting rod, an eccentric cam and suitable gearing such that the porcelain plate is moved, once only, back and forth beneath the porcelain peg for a distance of 10 mm. The porcelain peg may be loaded with, for example, 120 or 360 newtons.

The flat porcelain plates are made from white technical porcelain (roughness 9 to 32 μm) and have the dimensions 25 mm (length) × 25 mm (width) × 5 mm (height). The cylindrical porcelain peg is also made of white technical porcelain and is 15 mm long, has a diameter of 10 mm and roughened spherical end surfaces with a radius of curvature of 10 mm.

1.6.3.2.   Test conditions

The sample volume should be 10 mm³ or a volume to suit any alternative apparatus.

Solid substances are tested in the dry state and prepared as follows:

• (a) powdered substances are sieved (sieve size 0,5  mm); all that has passed through the sieve is used for testing;

• (b) pressed, cast or otherwise condensed substances are broken into small pieces and sieved; the sieve fraction < 0,5  mm diameter is used for testing.

Substances normally supplied as pastes should be tested in the dry state where possible. If the substance cannot be prepared in the dry state, the paste (following removal of the maximum possible amount of diluent) is tested as a 0,5  mm thick, 2 mm wide, 10 mm long film, prepared with a former.

1.6.3.3.   Performance of the tests

The porcelain peg is brought onto the sample under test and the load applied. When carrying out the test, the sponge marks of the porcelain plate must lie transversely to the direction of the movement. Care must be taken that the peg rests on the sample, that sufficient test material lies under the peg and also that the plate moves correctly under the peg. For pasty substances, a 0,5  mm thick gauge with a 2 × 10 mm slot is used to apply the substance to the plate. The porcelain plate has to move 10 mm forwards and backwards under the porcelain peg in a time of 0,44 seconds. Each part of the surface of the plate and peg must only be used once; the two ends of each peg will serve for two trials and the two surfaces of a plate will each serve for three trials.

A series of six tests are performed with a 360 N loading. If a positive event is obtained during these six tests, a further series of six tests must be performed with a 120 N loading. In other apparatus, the sample is compared with the chosen reference substance using an established procedure (e.g. up-and-down technique, etc.).

1.6.3.4.   Evaluation

The test result is considered positive if an explosion (crepitation and/or a report or bursting into flame are equivalent to explosion) occurs at least once in any of the tests with the specified friction apparatus or satisfies the equivalent criteria in an alternative friction test.

2. DATA

In principle, a substance is considered to present a danger of explosion in the sense of the directive if a positive result is obtained in the thermal, shock or friction sensitivity test.

3. REPORTING

3.1.   TEST REPORT

The test report shall, if possible, include the following information:

• — identity, composition, purity, moisture content, etc. of the substance tested,

• — the physical form of the sample and whether or not it has been crushed, broken and/or sieved,

• — observations during the thermal sensitivity tests (e.g. sample mass, number of fragments, etc.),

• — observations during the mechanical sensitivity tests (e.g. formation of considerable amounts of smoke or complete decomposition without a report, flames, sparks, report, crepitation, etc.),

• — results of each type of test,

• — if alternative apparatus has been used, scientific justification as well as evidence of correlation between results obtained with specified apparatus and those obtained with equivalent apparatus must be given,

• — any useful comments such as reference to tests with similar products which might be relevant to a proper interpretation of the results,

• — all additional remarks relevant for the interpretation of the results.

3.2.   INTERPRETATION AND EVALUATION OF RESULTS

The test report should mention any results which are considered false, anomalous or unrepresentative. If any of the results should be discounted, an explanation and the results of any alternative or supplementary testing should be given. Unless an anomalous result can be explained, it must be accepted at face value and used to classify the substance accordingly.

4. REFERENCES

• (1)Recommendations on the Transport of Dangerous Goods: Tests and criteria, 1990, United Nations, New York.

• (2)Bretherick, L., Handbook of Reactive Chemical Hazards, 4th edition, Butterworths, London, ISBN 0-750-60103-5, 1990.

• (3)Koenen, H., Ide, K.H. and Swart, K.H., Explosivstoffe, 1961, vol. 3, 6-13 and 30-42.

• (4)NF T 20-038 (September 85) Chemical products for industrial use — Determination of explosion risk.

Appendix

Example of material specification for thermal sensitivity test (see DIN 1623)

• (1)Tube: Material specification No 1.0336.505 g

• (2)Orifice plate: Material specification No 1.4873

• (3)Threaded collar and nut: Material specification No 1.3817

Figure 1

Thermal sensitivity test apparatus

(all dimensions in millimetres)

Image omitted; see official source

Text of image

Fig. 1a Steel tube and accessories

(1) tube

(1a) outer flange

(2) threaded collar; low-friction thread

(3) orifice plate a = 2,0 or 6,0 mm diameter

(4) nut b = 10 mm diameter

(5) chamfered surface

(6) 2 flat for spanner size 41

Fig. 1b Heating and protective device

(7) 2 flat for spanner size 36

(8) splinter-proof box

(9) 2 supporting rods for tube

(10) assembled tube

(11) position for rear burner; the other burners are visible

(12) pilot jet

Figure 2

Thermal sensitivity test

(example of fragmentation)

Image omitted; see official source

Text of image

No explosion

No explosion

Explosion

Explosion

Explosion

Explosion

Figure 3

Heating rate calibration for thermal sensitivity test

Image omitted; see official source

Text of image

Temperature (°C)

Time (s)

Temperature/time curve obtained on heating dibutyl phtalate (27 cm³) in a closed (1,5  mm orifice plate) tube using a propane flow rate of 3,2 litre/minute. The temperature is measured with a 1 mm diameter stainless steel sheathed chromel/alumel thermocouple, placed centrally 43 mm below the rim of the tube. The heating rate between 135 ^oC and 285 ^oC should be between 185 and 215 K/minute.

Figure 4

Shock test apparatus

(all dimensions in millimetres)

Image omitted; see official source

Text of image

Fig. 4a Fall-hammer, front and side, general view

(1) base, 450 x 450 x 60

(2) steel block, 230 x 250 x 200

(3) anvil, 100 diameter x 70

(4) column

(5) median cross-member

(6) 2 guides

(7) toothed rack

Fig. 4b Fall-hammer, lower part

(8) graduated scale

(9) fall-hammer (drop mass)

(10) holding and releasing device

(11) locating plate

(12) intermediate anvil (interchangeable), 26 diameter x 26

(13) locating ring with orifices

(14) impact device

Figure 4

Continued

Image omitted; see official source

Text of image

Fig. 4c Shock device for substances in powdered or paste-like form

Fig. 4d Shock device for liquid substances

(1) steel cylinders

(2) guide ring for steel cylinders

(3) locating ring with orifices

(a) vertical section

(b) plan

(4) rubber ring

(5) liquid substance (40 mm³)

(6) space free from liquid

Fig. 4e Hammer (drop mass of 5 kg)

(1) suspension spigot

(2) height marker

(3) positioning groove

(4) cylindrical striking head

(5) rebound catch

Figure 5

Friction sensitivity apparatus

Image omitted; see official source

Text of image

Fig. 5a Friction apparatus; elevation and plan view

(1) steel base

(2) movable carriage

(3) porcelain plate, 25 x 25 x 5 mm, held on carriage

(4) fixed porcelain peg, 10 diameter x 15 mm

(5) sample under test, approximately 10 mm³

Fig. 5b Starting position of peg on sample

(6) peg-holder

(7) loading arm

(8) counterweight

(9) switch

(10) wheel for setting carriage at starting position

(11) direction to electric drive motor

A.15.   AUTO-IGNITION TEMPERATURE (LIQUIDS AND GASES)

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.16.   RELATIVE SELF-IGNITION TEMPERATURE FOR SOLIDS

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.17.   OXIDISING PROPERTIES (SOLIDS)

The full description of this test method has been deleted. The equivalent international test method, or other applicable test methods for the endpoint in question, appear in Table 1 of Part 0.

A.18.   NUMBER-AVERAGE MOLECULAR WEIGHT AND MOLECULAR WEIGHT DISTRIBUTION OF POLYMERS

1. METHOD

This Gel Permeation Chromatographic method is a replicate of the OECD TG 118 (1996). The fundamental principles and further technical information are given in reference (1).

1.1.   INTRODUCTION

Since the properties of polymers are so varied, it is impossible to describe one single method setting out precisely the conditions for separation and evaluation which cover all eventualities and specificities occurring in the separation of polymers. In particular, complex polymer systems are often not amenable to gel permeation chromatography (GPC). When GPC is not practicable, the molecular weight may be determined by means of other methods (see Appendix). In such cases, full details and justification should be given for the method used.

The method described is based on DIN Standard 55672 (1). Detailed information about how to carry out the experiments and how to evaluate the data can be found in this DIN Standard. In case modifications of the experimental conditions are necessary, these changes must be justified. Other standards may be used, if fully referenced. The method described uses polystyrene samples of known polydispersity for calibration and it may have to be modified to be suitable for certain polymers, e.g. water soluble and long-chain branched polymers.

1.2.   DEFINITIONS AND UNITS

The number-average molecular weight Mn and the weight average molecular weight Mw are determined using the following equations:

Image omitted; see official source	Image omitted; see official source

where,

Hi is the level of the detector signal from the baseline for the retention volume Vi,

Mi is the molecular weight of the polymer fraction at the retention volume Vi, and

n is the number of data points.

The breadth of the molecular weight distribution, which is a measure of the dispersity of the system, is given by the ratio Mw/Mn.

1.3.   REFERENCE SUBSTANCES

Since GPC is a relative method, calibration must be undertaken. Narrowly distributed, linearly constructed polystyrene standards with known average molecular weights Mn and Mw and a known molecular weight distribution are normally used for this. The calibration curve can only be used in the determination of the molecular weight of the unknown sample if the conditions for the separation of the sample and the standards have been selected in an identical manner.

A determined relationship between the molecular weight and elution volume is only valid under the specific conditions of the particular experiment. The conditions include, above all, the temperature, the solvent (or solvent mixture), the chromatography conditions and the separation column or system of columns.

The molecular weights of the sample determined in this way are relative values and are described as ‘polystyrene equivalent molecular weights’. This means that dependent on the structural and chemical differences between the sample and the standards, the molecular weights can deviate from the absolute values to a greater or a lesser degree. If other standards are used, e.g. polyethylene glycol, polyethylene oxide, polymethyl methacrylate, polyacrylic acid, the reason should be stated.

1.4.   PRINCIPLE OF THE TEST METHOD

Both the molecular weight distribution of the sample and the average molecular weights (Mn, Mw) can be determined using GPC. GPC is a special type of liquid chromatography in which the sample is separated according to the hydrodynamic volumes of the individual constituents (2).

Separation is effected as the sample passes through a column which is filled with a porous material, typically an organic gel. Small molecules can penetrate the pores whereas large molecules are excluded. The path of the large molecules is thereby shorter and these are eluted first. The medium-sized molecules penetrate some of the pores and are eluted later. The smallest molecules, with a mean hydrodynamic radius smaller than the pores of the gel, can penetrate all of the pores. These are eluted last.

In an ideal situation, the separation is governed entirely by the size of the molecular species, but in practice it is difficult to avoid at least some absorption effects interfering. Uneven column packing and dead volumes can worsen the situation (2).

Detection is effected by, e.g. refractive index or UV-absorption, and yields a simple distribution curve. However, to attribute actual molecular weight values to the curve, it is necessary to calibrate the column by passing down polymers of known molecular weight and, ideally, of broadly similar structure e.g. various polystyrene standards. Typically a Gaussian curve results, sometimes distorted by a small tail to the low molecular weight side, the vertical axis indicating the quantity, by weight, of the various molecular weight species eluted, and the horizontal axis the log molecular weight.

1.5.   QUALITY CRITERIA

The repeatability (Relative Standard Deviation: RSD) of the elution volume should be better than 0,3  %. The required repeatability of the analysis has to be ensured by correction via an internal standard if a chromatogram is evaluated time-dependently and does not correspond to the above mentioned criterion (1). The polydispersities are dependent on the molecular weights of the standards. In the case of polystyrene standards typical values are:

Mp < 2 000	Mw/Mn < 1,20
2 000 ≤ Mp ≤ 106	Mw/Mn < 1,05
Mp > 106	Mw/Mn < 1,20

(Mp is the molecular weight of the standard at the peak maximum)

1.6.   DESCRIPTION OF THE TEST METHOD

1.6.1.   Preparation of the standard polystyrene solutions

The polystyrene standards are dissolved by careful mixing in the chosen eluent. The recommendations of the manufacturer must be taken into account in the preparation of the solutions.

The concentrations of the standards chosen are dependent on various factors, e.g. injection volume, viscosity of the solution and sensitivity of the analytical detector. The maximum injection volume must be adapted to the length of the column, in order to avoid overloading. Typical injection volumes for analytical separations using GPC with a column of 30 cm × 7,8  mm are normally between 40 and 100 μl. Higher volumes are possible, but they should not exceed 250 μl. The optimal ratio between the injection volume and the concentration must be determined prior to the actual calibration of the column.

1.6.2.   Preparation of the sample solution

In principle, the same requirements apply to the preparation of the sample solutions. The sample is dissolved in a suitable solvent, e.g. tetrahydrofuran (THF), by shaking carefully. Under no circumstances should it be dissolved using an ultrasonic bath. When necessary, the sample solution is purified via a membrane filter with a pore size of between 0,2 and 2 μm.

The presence of undissolved particles must be recorded in the final report as these may be due to high molecular weight species. An appropriate method should be used to determine the percentage by weight of the undissolved particles. The solutions should be used within 24 hours.

1.6.3.   Apparatus

• — solvent reservoir,

• — degasser (where appropriate),

• — pump,

• — pulse dampener (where appropriate),

• — injection system,

• — chromatography columns,

• — detector,

• — flowmeter (where appropriate),

• — data recorder-processor,

• — waste vessel.

It must be ensured that the GPC system is inert with regard to the utilised solvents (e.g. by the use of steel capillaries for THF solvent).

1.6.4.   Injection and solvent delivery system

A defined volume of the sample solution is loaded onto the column either using an auto-sampler or manually in a sharply defined zone. Withdrawing or depressing the plunger of the syringe too quickly, if done manually, can cause changes in the observed molecular weight distribution. The solvent-delivery system should, as far as possible, be pulsation-free ideally incorporating a pulse dampener. The flow rate is of the order of 1 ml/min.

1.6.5.   Column

Depending on the sample, the polymer is characterised using either a simple column or several columns connected in sequence. A number of porous column materials with defined properties (e.g. pore size, exclusion limits) are commercially available. Selection of the separation gel or the length of the column is dependent on both the properties of the sample (hydrodynamic volumes, molecular weight distribution) and the specific conditions for separation such as solvent, temperature and flow rate (1)(2)(3).

1.6.6.   Theoretical plates

The column or the combination of columns used for separation must be characterised by the number of theoretical plates. This involves, in the case of THF as elution solvent, loading a solution of ethyl benzene or other suitable non-polar solute onto a column of known length. The number of theoretical plates is given by the following equation:

Image omitted; see official source	or	Image omitted; see official source

where,

N	=	the number of theoretical plates
---	---	---
Ve	=	the elution volume at the peak maximum
---	---	---
W	=	the baseline peak width
---	---	---
W1/2	=	the peak width at half height

1.6.7.   Separation efficiency

In addition to the number of theoretical plates, which is a quantity determining the bandwidth, a part is also played by the separation efficiency, this being determined by the steepness of the calibration curve. The separation efficiency of a column is obtained from the following relationship:

Image omitted; see official source

where,

Ve, Mx	=	the elution volume for polystyrene with the molecular weight Mx
---	---	---
Ve,(10.Mx)	=	the elution volume for polystyrene with a ten times greater molecular weight

The resolution of the system is commonly defined as follows:

Image omitted; see official source

where,

Ve1, Ve2	=	the elution volumes of the two polystyrene standards at the peak maximum
---	---	---
W1, W2	=	the peak widths at the base-line
---	---	---
M1, M2	=	the molecular weights at the peak maximum (should differ by a factor of 10)

The R-value for the column system should be greater than 1.7 (4).

1.6.8.   Solvents

All solvents must be of high purity (for THF purity of 99,5  % is used). The solvent reservoir (if necessary in an inert gas atmosphere) must be sufficiently large for the calibration of the column and several sample analyses. The solvent must be degassed before it is transported to the column via the pump.

1.6.9.   Temperature control

The temperature of the critical internal components (injection loop, columns, detector and tubing) should be constant and consistent with the choice of solvent.

1.6.10.   Detector

The purpose of the detector is to record quantitatively the concentration of sample eluted from the column. In order to avoid unnecessary broadening of peaks the cuvette volume of the detector cell must be kept as small as possible. It should not be larger than 10 μl except for light scattering and viscosity detectors. Differential refractometry is usually used for detection. However, if required by the specific properties of the sample or the elution solvent, other types of detectors can be used, e.g. UV/VIS, IR, viscosity detectors, etc.

2. DATA AND REPORTING

2.1.   DATA

The DIN Standard (1) should be referred to for the detailed evaluation criteria as well as for the requirements relating to the collecting and processing of data.

For each sample, two independent experiments must be carried out. They have to be analysed individually.

Mn, Mw, Mw/Mn and Mp must be provided for every measurement. It is necessary to indicate explicitly that the measured values are relative values equivalent to the molecular weights of the standard used.

After determination of the retention volumes or the retention times (possibly corrected using an internal standard), log Mp values (Mp being the peak maxima of the calibration standard) are plotted against one of those quantities. At least two calibration points are necessary per molecular weight decade, and at least five measurement points are required for the total curve, which should cover the estimated molecular weight of the sample. The low molecular weight end-point of the calibration curve is defined by n-hexyl benzene or another suitable non-polar solute. The number average and the weight-average molecular weights are generally determined by means of electronic data processing, based on the formulas of section 1.2. In case manual digitisation is used, ASTM D 3536-91 can be consulted (3).

The distribution curve must be provided in the form of a table or as figure (differential frequency or sum percentages against log M). In the graphic representation, one molecular weight decade should be normally about 4 cm in width and the peak maximum should be about 8 cm in height. In the case of integral distribution curves the difference in the ordinate between 0 and 100 % should be about 10 cm.

2.2.   TEST REPORT

The test report must include the following information:

2.2.1.   Test substance:

• — available information about test substance (identity, additives, impurities),

• — description of the treatment of the sample, observations, problems.

2.2.2.   Instrumentation:

• — reservoir of eluent, inert gas, degassing of the eluent, composition of the eluent, impurities,

• — pump, pulse dampener, injection system,

• — separation columns (manufacturer, all information about the characteristics of the columns, such as pore size, kind of separation material, etc., number, length and order of the columns used),

• — number of the theoretical plates of the column (or combination), separation efficiency (resolution of the system),

• — information on symmetry of the peaks,

• — column temperature, kind of temperature control,

• — detector (measurement principle, type, cuvette volume),

• — flowmeter if used (manufacturer, measurement principle),

• — system to record and process data (hardware and software).

2.2.3.   Calibration of the system:

• — detailed description of the method used to construct the calibration curve,

• — information about quality criteria for this method (e.g. correlation coefficient, error sum of squares, etc.),

• — information about all extrapolations, assumptions and approximations made during the experimental procedure and the evaluation and processing of data,

• — all measurements used for constructing the calibration curve have to be documented in a table which includes the following information for each calibration point: — name of the sample, — manufacturer of the sample, — characteristic values of the standards Mp, Mn, Mw, Mw/Mn, as provided by the manufacturer or derived by subsequent measurements, together with details about the method of determination, — injection volume and injection concentration, — Mp value used for calibration, — elution volume or corrected retention time measured at the peak maxima, — Mp calculated at the peak maximum, — percentage error of the calculated Mp and the calibration value.

2.2.4.   Evaluation:

• — evaluation on a time basis: methods used to ensure the required reproducibility (method of correction, internal standard, etc.),

• — information about whether the evaluation was effected on the basis of the elution volume or the retention time,

• — information about the limits of the evaluation if a peak is not completely analysed,

• — description of smoothing methods, if used,

• — preparation and pre-treatment procedures of the sample,

• — the presence of undissolved particles, if any,

• — injection volume (μl) and injection concentration (mg/ml),

• — observations indicating effects which lead to deviations from the ideal GPC profile,

• — detailed description of all modifications in the testing procedures,

• — details of the error ranges,

• — any other information and observations relevant for the interpretation of the results.