A Composed Matching Algorithm of Spectrum Pre-Search and Precision Search Based on Wavelet Transform

Aim to the problems of the number of reference spectrum was still more after pre-search and false positive or false negative because of traditional method couldn’t use the detail information effectively in the identification process, a composed matching method of spectrum pre-search and identification based on wavelet transform was presented. It used the approximation of the wavelet in spectrum pre-search and the detail in spectrum identification. It presented that the decomposition level was 1 and the similarity threshold was 0.6—0.7 in the second pre-search，while the decomposition level was 3 in the identification. The detail information of wavelet was added in the similarity calculation to improve accuracy. According to the resolution of spectrometry, the decomposition level was setted based on the relation between peak width and scale of wavelet. In the accuracy experiment, 1 000 spectra was searched in the NIST 08 reference library(191 000 spectra) using the presented method, compared with weighted dot-product and Stein and Scott composed methods, the accuracy was improved by 24.9% and 1.9% in average. Searching the spectrum of samples through the spectrometry in the reference library, the results showed that it could improve the similarity and accuracy, and compared with that of Stein and Scott composed method, the similarity value of DMMP was improved by 7.6%, and that of perfluorotributylamine spectrum was 20.7%, and that of different concentration’s octafluoronaphthalene spectrum was improved by 14.9% in average, and especially acquired good result in the low concentration samples. Using the presented method to process the O-xylene spectra could improve the selectivity of similar compound.