VOC Emission Method:
As we all know, the main components of VOC are: hydrocarbons (such as benzene series, alkane, etc.), aldehydes and ketones (such as formaldehyde, acetaldehyde, acrolein, etc.).
Currently, vehicle factory mainly control 8 basic substance like: Benzene, toluene, ethylbenzene, xylene, styrene, formaldehyde, acetaldehyde, acrolein.
Here we come to understand the current two mainstream detection methods: 1, bag method/chamber method, 2, thermal desorption method.
1, Bag method/Chamber method
At present, Bag/chambe VOC detection method is a popular way for VOC detection used in China. The basic detection principles and procedures are:
A. The testing specimen is placed in a sealed sampling bag and then a certain amount of nitrogen gas is introduced into the sampling bag. After heating, the sample is heated. The VOC is volatilized into the bag and the VOC material is collected into the adsorption tube through the airway tube and the constant flow sampler. The hydrocarbons are captured by TENAX. The aldehydes and ketones are captured by DNPH. Finally, the substances are analyzed by ATD-GC/MS and HPLC. The amount of evaporation.
B. The testing specimen is placed directly in testing chamber,control the chamber inner environment conditions according to testing standard,like temperature, humidity, air exchange rate, back ground concentration air speed.etc. After a certain time period,the testing specimen VOC will be released out, VOC material is collected into the adsorption tube through the airway tube and the constant flow sampler. The hydrocarbons are captured by TENAX. The aldehydes and ketones are captured by DNPH. Finally, the substances are analyzed by ATD-GC/MS and HPLC. The amount of evaporation.
2, Thermal desorption method
Europe and the United States mainly use this method to detect VOCs. The basic detection principles and procedures are: After the sample is cut into small strips, it is put into a desorption tube, and thermal desorption is performed at 90 degrees for 30 minutes. GC analysis is performed. The peak time is based on the standard curve of toluene. For all peaks within C20, perform semi-quantitative analysis to obtain the total VOC value or the quantification of individual substances. Put the desorption tube that has been tested for VOC test on the ATD and re-desorb it for 120 minutes at 120 degrees. Into the GC analysis, another chromatogram data is obtained. According to the calibration curve of 16 carbons, the peak time is at C16–C32. Between all peaks, a semi-quantitative analysis was performed to obtain the total atomization volatilization.
At present, VOC mainly uses these two methods for detection. Among them, the bag method/chamber method is most widely used in China. However, due to the different standards of various companies, the detection methods are also different, mainly reflected in the heating temperature. Currently, the following heating temperatures are common in China: 40 degrees, 60 degrees, 65 degrees.
In addition, the following two points are important when testing bags with VOCs:
1, The aging sample bag will release a lot of VOC, so the sample bag can not be reused for many times. 3-5 times are enough.
2. The VOC back ground in the test chamber must be controlled as low as possible