GB/T 31106-2014Determination of volatile organic compounds in furniture (English PDF)

3.1 Volatile organic compounds (VOC)

It refers to the organic compound released from the sample AND capable of being detected in the outlet gas of the test equipment.

Note: The outlet of the test equipment refers to the gas outlet of the equipment that tests the release of volatile organic compounds from furniture, including sampling ports designed to collect gas samples. For example, when using the climate chamber method to test the volatile organic compound release from furniture, the outlet of the test equipment refers to the exhaust port of the climate chamber OR the sampling port of the climate chamber.

4.1.2.8 Sodium thiosulfate standard titration solution [c(Na2S2O3) = 0.1000

mol/L]. It may purchase standard reagent OR otherwise conduct preparation and calibration in accordance with the provisions of GB/T 601.

ADD 20 mL of sulfuric acid solution (4.1.2.7); LET it standing for 15 min again.

USE the sodium thiosulfate standard titration solution (4.1.2.8) to titrate it, until the solution shows pale yellow; ADD 1mL of starch solution (4.1.2.9);

CONTINUE titration until the blue color disappears; RECORD the volume of the sodium thiosulfate standard titration solution volume (V2) used. At the same time, USE water to do reagent blank titration; RECORD the volume of the sodium thiosulfate standard titration solution volume (V2) used for blank Bg - Calculation factor obtained from the drawn standard curve (4.1.5.1), in micrograms (µg); d - Dilution factor;

V0 - Sampling volume after converted into the standard state, in liters (L). The calculation result is retained with two significant digits.

4.1.7 Measurement range, interference and exclusion

4.1.7.1 Measuring range

USE 5 mL of sample solution, AND the determination range of this method is 0.1 µg ~ 1.5 µg; if the sampling volume is 20 L, the determinable concentration range is 0.01 mg/m³ ~ 0.15 mg/m³.

4.1.7.2 Interference and exclusion

The 20 µg phenol, 2 µg aldehyde and nitrogen dichloride have no interference with this method. The co-existence of the sulfur dioxide will make the determination result slightly low. Therefore, the interference from sulfur dioxide shall not be ignored; AND it may make the gas sample firstly pass through the manganese sulfate filter paper to remove the sulfur dioxide.

4.1.8 Precision

4.1.8.1 Repeatability

The absolute difference between the two independent test results obtained under the repeatability condition is not more than 20% of the arithmetic mean of the two determined values, based on the preconditions that the cases exceeding 20% of the arithmetic mean of the two determined values do not exceed 5%.

4.1.8.2 Reproducibility

The absolute difference between the two independent test results obtained under the reproducibility condition is not more than 40% of the arithmetic mean of the two measured values, based on the preconditions that the cases exceeding 40% of the arithmetic mean of the two determined values do not exceed 5%.

4.2 Method 2. chromotropic acid spectrophotometry

4.2.1 Principle

5.2.1.1 Standard gas

PREPARE the mixed standard gas containing each compound gas component to be determined at concentration about 100 µg/m3. It may also purchase the certified mixed standard gas.

5.2.1.2 Liquid standard substances

Each solvent to be tested is chromatographic pure which is not affected by the compound that co-eluting with the compound to be tested.

5.2.1.3 Calibration of mixed solution

USE the liquid standard substance of 5.2.1.2 to prepare it; USE the methanol solution as the dilution solvent. It may also purchase the certified mixed standard gas.

5.2.1.3.1 A solution containing about 10 mg/mL of each liquid standard substance

ADD 50 mL of methanol solution into a 100 mL volumetric flask; accurately WEIGH 1 g (accurate to 0.001 g) of liquid standard substance into this volumetric flask; it may weigh and place several liquid standard substances into the same volumetric flask, AND start weighing from the liquid standard substance of the weakest volatility. USE the methanol solution to make the volume reach to the mark; SHAKE it uniformly. […]