Examination of Wide Use Target Screening System for GC/MS

Abstract

Since the number and volume of the chemical substances that we use has been increasing rapidly, effective tools are necessary to examine not only regulated chemicals, but also unregulated chemicals for evaluating the safety of foods and the environment and to investigate the causes of environmental pollution accidents. There are two conventional techniques to identify unknown substances in samples by GC/MS: mass spectra library search and automated identification and quantification system with a newly developed database (AIQS-DB). However, there are some restrictions in both techniques: a mass spectra library search needs standard substances for confident identification, and AIQS-DB needs a specific instrument. In this study, we investigated a novel target screening system for GC―MS by which every GC―MS on the market can certainly identify a large number of substances registered in a database without the use of standards. The developed system is composed of a freeware, "Automated Mass Spectral Deconvolution and Identification System" provided by National Institute of Standards and Technology and two private libraries [programed temperature retention indices (PTRI) and mass spectra]. By using n-alkanes as PTRI, under the same GC condition, the retention times of the chemicals in samples were exactly predicted with an error for less than 3 s in three different instruments from different GC/MS makers. From accurate predictions of the retention times and mass spectra, reliable identification was achieved with different instruments. Although the number of chemicals registered in the database is only 1000, since substance registration to the private libraries is easy, we can register thousands of substances in the database for achieving various purposes, such as finding causes of environmental pollution, evaluating the safety of foods and the environment and finding illicit drugs.