[Simultaneous determination of monosaccharide and oligosacpharide in rice wine by high performance anion exchange chromatography with integrated pulsed amperometric detection and the establishment of their fingerprints].

An analytical method for the determination of glucose, fructose, isomaltose, isomaltotriose, maltose, panose and maltotriose was developed by high performance anion exchange chromatography coupled with integrated pulsed amperometric detection. The analysis was performed on a CarboPa™ 10 column with gradient elution of NaOH-NaOAc as mobile phases. The seven sugars were well separated in less than 26 min and showed good linear correlation coefficients between 0.5 and 50 mg/L. The detection limits (LODs) were 0.1 g/L. The recoveries ranged from 76.5% to 108.4% at different spiked levels. The relative standard deviations were between 3.02% and 8.23%. The established method was applied in determining the seven sugars in different batches of Shaoxing Jiafan rice wines from different manufacturers. The standard fingerprints were established by median values using the obtained results. Similarities of the fingerprints of the samples to the standard were calculated by using angle cosine. The results showed that the similarities of wines from different manufacturers were significantly different, so the method could be used for the identification of rice wines from different manufacturers.

Determination of four flavorings in infant formula by solid-phase extraction and gas chromatography-tandem mass spectrometry.

Increasing attention has been focused on the artificial flavorings added in foods, especially those for infants and children. For the first time, a sensitive and efficient analytical method based on gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the simultaneous identification and quantification of four flavoring agents (vanillin, methylvanillin, ethylvanillin, and coumarin) in infant formula samples. The flavorings in samples were extracted with methanol/water (v/v, 1:1), cleaned up by solid-phase extraction, and determined by GC-MS/MS in selected reaction monitoring (SRM) mode. Both isotope-labeled internal standards and matrix-matched calibration solutions were used to correct the matrix effects. The limit of quantification (LOQ) was calculated as 10 times the standard deviation, and it was 10.0 µg kg (-1) for vanillin, methylvanillin, ethylvanillin, and coumarin. The average recoveries were in the range of 82.8-107.5% with relative standard deviations (RSDs) below 8.9% measured at three concentration levels (10, 50, and 100 µg kg(-1)). The proposed method is suitable for the sensitive and accurate simultaneous determination of four flavoring agents in infant formula samples and also provided potential use for reference in terms of real analysis of other foods.

[Determination of eight pesticide residues in tea by liquid chromatography-tandem mass spectrometry and its uncertainty evaluation].

A method was developed for the determination of eight pesticide residues (fipronil, imidacloprid, acetamiprid, buprofezin, triadimefon, triadimenol, profenofos, pyridaben) in tea by liquid chromatography-tandem mass spectrometry. The sample was extracted by accelerated solvent extraction with acetone-dichloromethane (1:1, v/v) as solvent, and the extract was then cleaned-up with a Carb/NH2 solid phase extraction (SPE) column. The separation was performed on a Hypersil Gold C, column (150 mm x 2. 1 mm, 5 microm) and with the gradient elution of acetonitrile and 0. 1% formic acid. The eight pesticides were determined in the modes of electrospray ionization (ESI) and multiple reaction monitoring (MRM). The analytes were quantified by matrix-matched internal standard method for imidacloprid and acetamiprid, by matrix-matched external standard method for the other pesticides. The calibration curves showed good linearity in 1 - 100 microg/L for fipronil, and in 5 -200 microg/L for the other pesticides. The limits of quantification (LOQs, S/N> 10) were 2 p.g/kg for fipronil and 10 microg/kg for the other pesticides. The average recoveries ranged from 75. 5% to 115.0% with the relative standard deviations of 2.7% - 7.7% at the spiked levels of 2, 5, 50 microg/kg for fipronil and 10, 50, 100 microg/kg for the other pesticides. The uncertainty evaluation for the results was carried out according to JJF 1059-1999 "Evaluation and Expression of Uncertainty in Measurement". Items constituting measurement uncertainty involved standard solution, weighing of sample, sample pre-treatment, and the measurement repeatability of the equipment were evaluated. The results showed that the measurement uncertainty is mainly due to sample pre-treatment, standard curves and measurement repeatability of the equipment. The method developed is suitable for the conformation and quantification of the pesticides in tea.

[Determination of 14 pesticide residues in sulfur-containing vegetables by gas chromatography-negative chemical ionization mass spectrometry].

A gas chromatography-negative chemical ionization mass spectrometric (GC-NCI/ MS) method has been developed for analyzing 14 pesticide residues in sulfur-containing vegetables (scallion, garlic, garlic bolt, leek, etc.). The samples were first heated in a microwave oven to eliminate most of the sulfur-containing interfering impurities and then extracted with acetonitrile. The extracts were further cleaned-up by gel permeation chromatography (GPC) and a primary-secondary amine (PSA) cartridge. The target analytes were determined using GC-NCI/MS in the selected ion monitoring (SIM) mode. The recoveries of all the pesticides (at spiked level of 50 microg/kg) were from 49.2% to 113.1% with the relative standard deviations between 1.42% and 8.70%. The detection limits (S/N = 3) were in the range of 0.5-10.0 microg/kg. The method is selective without interference and suitable for the determination and confirmation of pesticides in the sulfur-containing vegetables.