GB/T 39897-2021Determination of volatile organic compounds and aldehydes and ketones in nonmetallic parts of vehicles (English PDF)

3.1 Volatile Organic Compounds

Volatile organic compounds refer to the generic term of compounds, such as: benzene, toluene, ethylbenzene, xylene and styrene, which are measured in accordance with Appendix A.

3.2 Aldehydes and Ketones

Aldehydes and ketones refer to the generic term of compounds, such as: formaldehyde, Tenax tube refers to a glass or stainless-steel sampling tube with at least 200 mg of adsorbents inside, for example, poly (di) phenylene oxide (polyphenylene oxide).

3.12 DNPH Tube

DNPH tube refers to a sampling tube filled with 2,4-dinitrophenylhydrazine (DNPH)- coated silica gel.

3.13 PE Film

PE film refers to a type of film that is made of polyethylene and extensively applied to industrial packaging.

4.1 Sample Preparation

The samples shall be in the state of supply. Before delivery, the samples shall be stored at room temperature. Meanwhile, the environmental conditions (temperature and relative humidity) of storage shall be recorded.

4.2 Sample Packaging

4.2.1 Within a specified time after the production is offline (the time shall be negotiated by the demand-side and the supply-side, and indicated in the test report), use non-polluting aluminum foil and / or odorless PE film to seal and pack the samples. Then, place them in the packaging box.

4.2.2 The packaging and shipping mark of the samples shall take Table 1 in GB/T 6388- 1986 as a reference.

4.3 Sample Transportation

During sample transportation, it is advisable to avoid direct exposure of the samples to strong light or high-temperature environment; avoid damage to the packaging.

4.4 Sample Reception

After receiving the samples, the laboratory shall store the samples in a well-packaged state in an environment of 23 °C ± 5 °C.

A.1 Principle

Use solid adsorbent to collect the volatile organic compounds in the air of the bag; place the Tenax tube in the thermal desorption instrument; after being separated by gas chromatography, use mass spectrometry for detection. Conduct qualitative determination through the comparison with the standard mass spectrum of the target substance to be tested and the retention time; adopt the external standard method or internal standard method for quantitative determination.

A.2 Reagents and Materials

A.2.1 Standard sample (reference substance)

Prepare standard gas or liquid; use a constant-flow gas sampler to quantitatively collect it in the activated sampling tube, so as to form a series of reference substances.

The analyte concentration of the series of prepared reference substances is approximate to the concentration of the sample to be analyzed. It is also feasible to directly use a micro-injector to take a certain volume of the prepared reference substances with a series of concentrations; inject it into the TENAX tube; under the condition of a nitrogen flow rate of 100 mL/min, continuously use nitrogen to blow for 1 min ~ 2 min; take it as a reference tube.

A.2.2 Carrier gas

The carrier gas shall use 99.999% high-purity helium. The carrier gas circuit shall be equipped with purification systems, such as: oxygen and organic filters.

A.2.3 Adsorbent

The adsorbent is a solid phase with a particle size of 180 µm ~ 250 µm. Before being installed in the tube, the adsorbent shall be activated with inert gas flow under the maximum allowable operating temperature, cooled and sealed, and stored at a low temperature. During use, the desorption temperature shall be lower than the activation temperature.

A.3 Instruments and Equipment

A.5.3.1 Use a constant-flow gas sampler to respectively and accurately extract 100 mL, 400 mL, 1 L, 4 L and 10 L of 100 µg/m3 standard gas to pass through the sampling tube; take them as a standard series. Or use a micro-injector to inject the reference substance; take the series of standard tubes obtained through nitrogen blowing as a standard series.

A.5.3.2 Adopt the thermal desorption gas chromatography - mass spectrometry to analyze the standard series. Take the mass of the target component as the x-coordinate; take the characteristic mass ion peak area (or peak height) after deducting the blank response as the y-coordinate; draw the calibration curve. The slope of the calibration curve is the response factor (RF); the linear correlation coefficient shall at least reach 0.995. If the calibration curve really cannot pass through the zero point, then, the equation of the curve shall include the intercept.

A.5.3.3 Each new calibration curve shall be analyzed and verified through a reference substance from different sources. The reference substance shall be consecutively analyzed for 6 times. Under the condition of a significance level of 5%, there shall be no significant difference between the analysis result and the nominal value of the reference substance, otherwise, correct measures shall be taken to eliminate the error caused by reference substance from two different sources.

A.5.3.4 The daily analysis and quality control is completed by the quality control chart.

Within a certain interval, take two parallel control samples and repeat the analysis for at least 20 times, so as to make a mean control chart (X Chart). In the daily analysis, in accordance with the frequency of sample determination, take two parallel control samples for simultaneous determination with the samples to be analyzed.

Successively mark the analysis results of the control samples on the control chart; in accordance with the following rules, judge whether the analysis process is in the state of control:

a) If this point is between the upper and lower warning lines, then, the test process is under control and the sample analysis result is valid;

b) If this point exceeds the upper and lower warning lines, however, it is still within the upper and lower control limits, then, this indicates that the analysis quality has begun to deteriorate and there is a tendency of losing control. Thus, a preliminary inspection shall be carried out and corresponding corrective measures shall be taken;

c) If this point falls beyond the upper and lower control limits, then, the causes shall be immediately checked and the samples shall be re-determined;

d) Although all the data are within the range of control, the continuous rise or fall of seven points indicates that the analysis process has a tendency of losing control. Thus, the causes shall be found out and corrected.

---Acetone is less than 0.30 µg/tube;

---Other substances are less than 0.10 µg/tube.

B.2.2 High-purity acetonitrile (mobile phase exclusive to HPLC)

UV grade purity. The mass concentration of formaldehyde shall be less than 1.5 µg/L. Keep it away from light.

B.2.3 Standard sample (reference substance)

B.2.3.1 Use standard gas or liquid or solid to prepare standard gas of required concentration. Use constant-flow gas sampler to quantitatively collect it in DNPH sampling tube to form a standard series. The concentration of the analyte in the prepared standard series is similar to the concentration of the samples to be analyzed.

During the collection, use the same flow rate as the sampling to collect the standard gas.

B.2.3.2 2,4-dinitrophenylhydrazone liquid standard sample (reference substance) of aldehydes and ketones may be directly purchased, or the solid standard sample (reference substance) may also be used to prepare the standard series by yourself.

B.2.4 Filter membrane

Use 0.45 µm filter membrane for the tests.

B.3 Instruments and Equipment

Use the following instruments and equipment for determination:

a) High performance liquid chromatograph (HPLC);

b) Micro-injector;

c) Solid phase extraction device and its accessories; d) Ultrasonic cleaner.

B.4 Sample Pre-treatment

B.4.1 Place the sampling tube on the solid phase extraction device for sample elution.

The flow direction of the eluent shall be opposite to the direction of the airflow during sampling.

B.4.2 Accurately add 5 mL of acetonitrile to reversely elute the sampling tube; collect the eluent in a 5 mL volumetric flask. Use 0.45 µm filter membrane to filter the eluent.

B.4.3 Use acetonitrile to reach a constant volume of 5 mL scale on the volumetric flask. reference substance, otherwise, correct measures shall be taken to eliminate the error caused by reference substance from two different sources.

A.5.2.5 The daily analysis and quality control is completed by the quality control chart.

Within a certain interval, take two parallel control samples and repeat the analysis for at least 20 times, so as to make a mean control chart (X Chart). In the daily analysis, in accordance with the frequency of sample determination, take two parallel control samples for simultaneous determination with the samples to be analyzed.

Successively mark the analysis results of the control samples on the control chart; in accordance with the following rules, judge whether the analysis process is in the state of control:

a) If this point is between the upper and lower warning lines, then, the test process is under control and the sample analysis result is valid;

b) If this point exceeds the upper and lower warning lines, however, it is still within the upper and lower control limits, then, this indicates that the analysis quality has begun to deteriorate and there is a tendency of losing control. Thus, a preliminary inspection shall be carried out and corresponding corrective measures shall be taken;

c) If this point falls beyond the upper and lower control limits, then, the causes shall be immediately checked and the samples shall be re-determined;

d) Although all the data are within the range of control, the continuous rise or fall of seven points indicates that the analysis process has a tendency of losing control. Thus, the causes shall be found out and corrected.

B.5.3 Sample analysis

In accordance with the operation steps of drawing the calibration curve and the same analysis conditions, analyze the samples.

B.6 Result Calculation

The mass concentration of the aldehydes and ketones shall be calculated in accordance with the stipulations of 6.3.

B.7 Quality Assurance and Control

B.7.1 Interference and elimination

B.7.1.1 Avoid exposing the DNPH sampling tube directly to sunlight.

B.7.1.2 Since the formaldehyde contained in acetonitrile may be quantitatively converted into hydrazone, the determined concentration of formaldehyde in the sample is relatively high. Hence, in the quality control procedure, formaldehyde in acetonitrile

D.1 Principle of Sampling

Place the sample in a uniformly mixed test chamber. Control the temperature, humidity and gas exchange rate in the chamber for conditioning. After a certain time, collect the gas in the chamber, so as to conduct qualitative and quantitative analysis on the organic substances released by the sample.

D.2 Sampling Devices

D.2.1 Test chamber

D.2.1.1 Volume of test chamber

The volume the test chamber may be chosen between 0.5 m³ ~ 4.0 m³. The standard test chamber has a volume of 1 m³ ± 0.05 m³ and has good air-tightness. In the test chamber, there shall be a gas mixing device, a bracket for placing the sample (to avoid contact between the sample and the inner wall of the chamber), and air intake and exhaust piping, etc.

D.2.1.2 Material of chamber

The inner wall of the chamber and the bracket for placing the sample should be made of electro-polished stainless steel. If the parts or facilities installed inside the chamber cannot be made of electro-polished stainless steel material, then, they shall be made of materials that have relatively weak adsorption towards the organic substances and do not release organic substances; the surface area of the parts or facilities using these materials cannot exceed 5% of the total surface area of the inner part of the chamber.

D.2.1.3 Air-tightness

In order to avoid uncontrollable air exchange, it is necessary to conduct air-tightness test on the test chamber. Under the condition of applying a positive pressure of 1,000 Pa in the test chamber, it shall be ensured that the amount of air leakage per minute is less than 0.5% of the chamber volume, or that the amount of air leakage is less than 5% of the supply air flow. In order to prevent the outside gas from entering the chamber, it shall be ensured that the internal pressure of the test chamber is slightly higher than the atmospheric pressure, which means it is operated under slightly positive pressure,

D.2.1.5 Chamber cleaning

By adopting suitable cleaning methods, for example, high-temperature thermal desorption, it shall be ensured that after each test, the test chamber is thoroughly cleaned. Before each test, a blank sample shall be collected to verify whether the background value of the chamber satisfies the test requirements.

D.2.2 Temperature adjustment

The temperature adjustment system in the chamber shall ensure that the temperature difference at each point inside the chamber does not exceed ± 1 °C.

D.2.3 Humidity adjustment

The humidity adjustment device shall be able to ensure that the gas entering the test chamber has a relative humidity of 45% at 23 °C and a relative humidity of 5% at 65 °C.

In addition, during the humidity adjustment, no steam or spray can be generated.

D.2.4 Clean gas supply

D.2.4.1 The mass concentration of total volatile organic compounds in the intake air shall not exceed 50 µg/m3; the mass concentration of single volatile organic compound shall not exceed 5 µg/m3.

D.2.4.2 It shall be ensured that the gas exchange rate is 0.4 m³/h; the gas supply flow rate in the chamber shall be set to 6.67 L/min ± 0.35 L/min (65 °C, ambient atmospheric pressure), with a deviation of less than ± 5%.

D.2.5 Total hydrocarbon concentration determination device

The test chamber shall be equipped with an online hydrogen flame ionization detector (FID) to implement real-time monitoring the total hydrocarbon concentration in the gas of the test chamber. The maximum sampling flow of FID shall not exceed 15 mL/min.

Use N-propane as the calibration gas; use nitrogen with a purity of 99.999% as the zero gas, or a special zero gas generator.

D.3 Preparation before Sampling

D.3.1 Chamber background

D.3.1.1 In order to assess the influence of links that might introduce pollutants on the test, such as: the air intake, the sealing ring and the cleanliness of the test chamber, before each test, the background concentration of the chamber shall be monitored.

The specific monitoring method is: at 65 °C, collect a background gas sample to respectively analyze the content of target pollutants in the background gas sample.

D.3.1.2 The total mass concentration of volatile organic components shall be less than