Determination of 29 Volatile Organic Compounds in Tea by Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry and Hazard Level Assessment

A method was developed for determination of 29 VOCs in tea by SPME-GC-MS, and a hazard level assessment was conducted on randomly selected 100 tea samples. Tea sample together with internal standard of phenylethyl acetate was added in headspace vials, the target compounds were adsorbed by DVB/CAR/PDMS fiber tip at equilibrium temperature of 60℃ for 30 min, and then introduced in to GC-MS in splitless mode after desorption. HP-FFAP chromatographic column was used as stationary phase for separation under temperature programmed condition. The target compounds obtained entered a mass spectrometer equipped with EI source, and deteted in selective ion monitoring (SIM) mode with internal standard method for quantification. The hazardous level of VOCs in tea was evaluated by food safety index (IFS). The results showed that the ratios between the mass fraction of 29 VOCs in the range of 0.05-0.50 mg·kg^-1 and those of internal standard were linearly related to the respective peak area ratios, with detection limits (3S/N) in the range of 0.001 6-0.031 6 mg·kg^-1. Recovery test was made on the actual samples by standard addition method, giving results in the range of 74.4%-86.6%, and RSDs (n=6) of measured values ranged from 2.4% to 8.9%. VOCs were all detected in 100 tea samples with total content of VOCs detected in the range of 0.035-0.113 mg·kg^-1, and value of maximum IFS (2.79×10^-3) was far less than 1, indicating that the potential hazardous level of VOCs in tea was acceptable.