Determination of Listeria Monocytogenes in Agricultural Products by-High Resolution Pyrolysis Gas Chromatography-Mass Spectrometry

Abstract

A method was developed for the qualitative determination of Listeria monocytogenes in the agricultural products by high resolution pyrolysis gas chromatography-mass spectrometry-selected ion monitoring(HPRGC/MS-MIS) technology.The method was accurate,highly sensitive and easy to operate.The operation conditions of HRPGC/MS system were as follows: pyrolysis conditions were as follows: starting temperature was 50 ℃,heating rate was 20 ℃/min,the temperature of the pyrolysis room was 230 ℃,and pyrolysis temperature was 650 ℃ for 10 s.Gas chromatography was accomplished with a carrier gas of helium at a flow rate of 0.9 mL/min.The GC column was a DB-WAXTER capillary column.The GC column temperature initially was kept at 45 ℃ for 4 min,then programmed to 100 ℃ at 6 ℃/min,200 ℃ at 10 ℃/min,250 ℃ at 12 ℃/min and held for 25 min.The total flow rate was spilt at ratio of 50 to 1.EI was used as ion source.The retention time of 19.056 min was selected for SIM,the ions of m/z were 54,98.L.monocytogens,two kinds of agricultural products with and without L.monocytogens samples were evaluated by this method according to the characteristics of the selected ion of L.monocytogens.An expected result was observed using the HRPGC/MS to detect L.monocytogens in different kinds of food,cucumber and beef.This method does not need the complex pre-treatment,the analysis time was comparatively short,and handing is easy for the operator.Retention time and mass spectra were used for qualitative analysis at the same time to eliminate the interference of different kinds of agricultural product impurities.The accurateness,good selectivity and reproducibility of the results demonstrate that HRPGC/MS is a useful method for rapid detection of L.monocytogens in agricultural products.