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A fast, sensitive, and reliable method for the determination of fipronil and its metabolites (fipronil-sulfone, fipronil sulfide, and fipronil-desulfynil) in eggs was developed by a modified quick,...

Aroma plays an important role in fruit quality and varies among different fruit cultivars. In this study, a sensitive and accurate method based on headspace solid-phase microextraction (HS-SPME) coupled with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC&times, GC-TOFMS) was developed to comprehensively compare aroma components of five pear cultivars. In total, 241 volatile compounds were identified and the predominant volatile compounds were esters (101 compounds), followed by alcohols (20 compounds) and aldehydes (28 compounds). The longyuanyangli has the highest relative concentration (838.12 ng/g), while the Packham has the lowest (208.45 ng/g). This study provides a practical method for pear aroma analysis using SPME and GC&times, GC-TOFMS.

An analytical method was developed for determination of multipesticide residues, including organophosphorus, organohalogen, pyrethroid, and organonitrogen, in tea at trace levels by GC coupled with triple quadrupole mass chromatography (QqQ-MS/MS). Scan time was selected in order to optimize QqQ-MS/MS conditions. The key parameters for controlling cleanup performance were optimized, including SPE cartridge type and elution solvent volume. Acetonitrile was the extraction solvent, and a novel multilayer SPE cartridge, Cleanert TPT, was used in the cleanup step. The recoveries of the studied pesticides at 5.0, 10.0, and 25.0 microg/kg were in the range of 77.8 to 103.8% with an RSD of less than 14%. Determination coefficient (R2) values between 0.9951 and 0.9998 were obtained for all target compounds. The LOD was between 0.002 and 1.0 microg/kg, and LOQs were 0.0066-3.3 microg/kg, which satisfied the maximum residue limits for pesticides in tea recommended by the European Union and Japan. The optimized method was applied to the analysis of real tea samples obtained from the local market.

A new method was developed for the determination of 12 polychlorinated biphenyls (PCBs) in meat and sea food by gas chromatography coupled to triple quadrupole mass spectrometry using selected reaction monitoring technique. The method was based on ultrasonic extraction and florisil column cleaning up. Recoveries of the 12 PCBs ranged from 70.4 % to 100.6 % and the relative standard deviations were from 0.5 % to 12.6 %. The limits of detection ranged from 0.006 to 0.009 μg/kg and the limits of quantitation ranged from 0.02 to 0.03 μg/kg. Eight meat and sea food samples were analyzed for the analysis of the polychlorinated biphenyls using the proposed method.

A rapid multi-residue method has been developed for the determination of 16 herbicides in garlic. The analytical procedure is based on prior microwave heating prevention of the generation of sulfur-containing compounds. The garlic samples which had been pretreated were extracted with acetonitrile and cleaned up by solid-phase extraction. The herbicide residues were detected by gas chromatography–mass spectrometry with selected ion monitoring. The recoveries of 16 herbicides ranged from 69.0 to 105.4% with the relative standard deviations (RSD) below 10.1%. The limit of quantification (LOQ) ranged from 0.003 to 0.015 mg kg−1.

In this work, we developed an efficient method to determine the ethylicin content in soil, cotton plant and cotton seed, and we also studied the fate of ethylicin in the cotton field ecosystem. The residual ethylicin was analyzed by GC-ECD. The limit of quantification was 0.005 mg/kg for soil, 0.01 mg/kg for the plant and cotton seed. The kinetics study of ethylicin residue showed that the ethylicin concentration in plant and soil can be regressively quantified as C = 1.0762e(-0.2529t) and C = 0.5535e(-0.1333t), representing a half-live of 2.7 and 5.2 days, respectively. As a conclusion, a dosage of 354 g a.i. ha(-1) was recommended, which could be considered as safe to human beings and animals.