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Sample preparation in accordance with the DIN EN ISO 17895 test method (determination of the in-can VOC content in water-soluble emulsion paints）

Posted Date:2025/6/24

8.2 Sample preparation

8.2.1General

Sample preparation involves diluting the sample (see 8.2.2) and preparing the test samples with standard additions (see 8.2.4) and without standard additions (see 8.2.3).

Carry out the sample preparation quickly since the original sample diluted with citrate buffer is prone to serum formation and losses can occur as the result of volatilization of individual compounds.

Figure 1 shows a diagram of the sample-preparation plan.

8.2.2Dilution of original sample

Weigh 10 g of the original sample and 10 g of citrate buffer (7.4) to the nearest 0,1 g into a 20 ml septum vial(6.4),seal and mix.

8.2.3Preparation of test samples for analysis without multiple standard additions

Vigorously shake the sealed septum vial containing the diluted sample (prepared as in 8.2.2), then immediately remove any excess vapour by piercing the septum with a 2 ml disposable syringe (6.3). For the analysis, weigh aliquots of (15 + 3) mg to the nearest 0,1 mg into each of three vials (6.4) and seal the latter immediately.

NOTE Higher initial test sample masses result in errors in the result due to the increase in pressure.

8.2.4 Preparation of test samples for analysis with multiple standard additions

Prepare four diluted samples as in 8.2.2 and add, using a 50 μl syringe (6.2), about 10 μl, 20 μl, 30 μl and40 μl of surrogate standard (7.2) (a different volume to each vial). Note the added amount to the nearest 0,1 mg. Close the vials firmly and mix well.

Shake the sealed vials vigorously once again, then remove any excess vapour by piercing the septum with a 2 ml disposable syringe (6.3). For the analysis, weigh an aliquot of about (15 + 3) mg of these diluted test samples containing standard additions to the nearest 0,1 mg into each of three empty vials (6.4) and seal the latter immediately.

NOTE If a standard addition for a certain coating matrix is not feasible, another representative coating matrix can be used alternatively for standard addition, Since the slope of the calibration curve is likely to be different when using another matrix, it was necessary to record this deviation in the test report.