ISO 23322:2021 Paints and varnishes — Determination of solvents in coating materials containing organic solvents only — Gas- chromatographic method

ISO 23322:2021 Paints and varnishes — Determination of solvents in coating materials containing organic solvents only — Gas- chromatographic method. 8 Sampling Take a representative sample, as described in ISO 15528. 9 Choice of sample injection system The choice between hot injection, cold injection and headspace injection depends on the type of the product under test. It will be necessary to use the cold injection system for products which at high temperature release substances which interfere with the determination. Indications of cleavage or decomposition reactions can be obtained by looking for changes in the chromatogram (e.g. the occurrence of foreign peaks or increase of peak size or peak broadening) at various sample injector temperatures. The two sample injection systems hot injection and cold injection have been studied in interlaboratory tests, where the following observations were made: The hot injection system includes all of the volatile constituents, solvents and cleavage products of the binders and additives. Cleavage products of the binders or additives which are identical to a solvent component can be separated by a cold injection system, since they elute later as a result of the programmed increase in injection block temperature. The headspace injector is primary used for samples with a low content of organic solvents. Headspace can only be used to analyse solvents with sufficient volatility at the controlled sample temperature. 10.5.1 Direct injection 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 10.3.2), 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. 10.5.2 Head space injection Sample preparation involves diluting the sample and preparing the test samples. If appropriate, standard additions can be used for quantification NOTE A possible standard addition method is described in detail in ISO 17895. Carry out the sample preparation quickly since the original sample...