Abstract:

The comparison method of fingerprints of the lacquer coat of cars (LCC) was established by using thermal desorption instrument with gas chromatography. The actual LCC samples were also analyzed. The samples were cut out to proper size and placed in the desorption furnace of the thermal desorption instrument. The volatile organic compounds in LCC were desorbed from the lacquer coat samples in the furnace under the chosen temperature, then separated in the capillary column and detected on a flame ionization detector of gas chromatography. The incipient judgment whether the two fingerprints of LCC were the same can be made from the contour and figure of the chromatograms. To make farther study of the two similar fingerprints, the overlap ratio of the peaks and relative retention values were given in the article. The two LCC samples can be regarded as the same if the overlap ratio of peaks was more than 90%, and the similarity of the ratio of relative retention times rt2 and rt1 and relative peak areas rA2 and rA1 in the two fingerprints were more than 99% and 70%, respectively. The method is good in repeatability and is easily carried out. The peaks in the fingerprint can be readily recognized. The fingerprint was characterized quantitatively. The method can be used in the department of traffic police and the comparison result can be used as material evidence in the court.

Key words: comparison, fingerprints, lacquer coat , online using of thermal desorption with gas chromatography