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×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×GC-TOFMS.

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.

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.

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