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Analysis in accordance with DIN EN ISO 11890-2 (Paints and varnishes - Determination of VOC and SVOC contents)

Posted Date:2025/8/5 1

8.2 Analysis

8.2.1 Sample preparation

Weigh a suitable amount of sample greater than 0,2 g (generally 1 g to 3 g is recommended) and an appropriate amount of the internal standard into a sample vial. Dilute the test sample with a suitable volume of extraction solvent (typically a dilution factor of 4 to 50 is applied, depending on the target compound concentration, see 7.7), seal the vial and homogenize the contents. When necessary, use methods such as stirring, vortexing or ultrasonic mixing to support extraction. If particles do not readily settle, phase cleaning can be obtained by centrifugation or filtration.

The internal standard concentration should be chosen at such level that detector signal precision and recovery from the pre-treated sample are optimal.

Repeat the procedure and perform at least a duplicate analysis.

8.2.2 Data acquisition for sample measurement

Set the instrumental parameters as optimized during calibration.

Determine the retention times of the marker compounds (see 9.2. These retention times define the integration end-point for the unidentifiable VOC and/or SVOC determination in the chromatogram if no other specifications are given.

Inject 0,1 μl to 1 μl of the test sample into the gas chromatograph and record the chromatogram. Determine the peak areas for each compound and allocate each peak to the VOC range or to the SVOC range as specified in 9.2.

8.3 Calibration

8.3.1 General

Where suitable calibration compounds are commercially available, the relative response factor shall be determined using multi point calibration.

8.3.2 Preparation of calibration solutions

Weigh, into a sample vial (6.9), to the nearest 0,1 mg, suitable amounts of the compounds determined in 9.1 which are of the same order of magnitude as their respective contents in the product under test.

Weigh a similar amount of the internal standard (7.2) into the sample vial, dilute the mixture with extraction solvent (see 7.7), and inject it under the same conditions as will be used for the test sample.

Repeat the procedure above two to seven times depending on the number of calibration points with different amounts, encompassing the respective contents in the product under test.

NOTE 1 Usually, a three- or five-point calibration is suitable.

NOTE 2 A one-point calibration is not suitable for the initial calibration of a compound because it does not allow to verify the linear relation between relative response and relative mass, see Figure 1.

8.3.3 Analysis of the multi-point calibration

Inject suitable amounts of the calibration solutions into the gas chromatograph. Plot the mass of the compound under investigation relative to the internal standard mass versus the peak area of compound i divided by the peak area of the internal standard.

Then carry out a linear regression to determine the slope of the curve, s_i. It represents the reciprocal of the compound specific relative response factor (CSRF), r_i. The function for linear regression, the relation between the slope of the curve and the CSRF and the calculation of the relative response factor, r_i, are given in the formulae (l,(2)and (3).

where

r_i is the CSRF (compound specific relative response factor);

s_i is the slope of the curve;

A_i is the peak area of compound i;

A_is is the peak area of the internal standard;

m_i is the mass, in grams, of compound i in the calibration solution,

m_is is the mass, in grams, of the internal standard in the calibration solution.

No offset other than statistical deviations should be observed. If a significant offset is recorded, results and the equipment should be checked and, if necessary, the analysis shall be repeated.

8.4 Quality assurance

Quality assurance may be used to check if the CSRF has changed and if a new calibration is necessary.

An appropriate, e.g. mid level, calibration solution can be used (see 8.3.2).

8.5 Gas chromatographic conditions

The gas-chromatographic conditions used depends on the product to be analysed and shall be optimized each time using a known calibration mixture.

The injection volume and the split ratio shall be coordinated so as not to exceed the capacity of the column and to remain within the linear range of the detector. Asymmetrical peaks will give an indication of overloading of the gas-chromatographic system.

Examples of suitable GC method conditions are given in Annex C

8.6 Density

If required by the calculation (see 11.3 to 11.5), determine the density of the sample using the part of ISO 2811 which will give the best precision for the type of sample concerned. Determine the density at 23 °C.

8.7 Water content

If required by the calculation (see 11.4 and 11.5), determine the water content, as a percentage by mass, by the method given in IS0 760, selecting the reagents so that there will be no interference from the compounds contained in the sample. If the compounds are not known, they shall be determined qualitatively(see 9.1).

NOTE 1 Typical compounds likely to cause interference are ketones and aldehydes. Reagent manufacturers normally publish literature for guidance on correct reagent selection.

NO'TE 2 If the product to be tested is well characterized and known not to contain water, it might not be necessary to determine the water content, which is, in this case, assumed to be zero.