Occurrence and exposure risk assessment of pesticide residues in green tea samples cultivated in Hangzhou area, China.

The concentration of pesticide residues in 105 green tea samples grown in Hangzhou area were investigated. Of the 14 pesticides analysed using gas chromatography-tandem mass spectrometry and the 27 pesticides analysed using liquid chromatography-tandem mass spectrometry, only 18 were detected in the tea samples. The most frequently detected pesticide residues were imidacloprid (35.

Monochloropropanediol in edible vegetable oils from Hangzhou market in China: occurrence and exposure risk assessment.

In this study, 241 vegetable-oil food samples were collected from the Hangzhou market in China and analysed for fatty acid esters of 3- and 2-monochloropropanediol (3-MCPD and 2-MCPD) using non-derivative gas chromatography tandem mass spectrometry (GC-MS/MS). Food consumption data were taken from a food consumption survey of urban and rural residents in Hangzhou city performed in 2010-2011. Levels of 3-MCPD esters in edible oil ranged from not detected to 7.

Rapid determination of nitrite in foods in acidic conditions by high-performance liquid chromatography with fluorescence detection.

In this study, a simple, rapid, and sensitive method for the determination of nitrite (NO2 (-) ) in food samples by high-performance liquid chromatography with fluorescence detection in acidic conditions had been developed. The derivatization of the nitrite with 2,3-diaminonaphthalene was performed in acidic conditions to yield the highly fluorescent 2,3-naphthotriazole, which was directly analyzed by high-performance liquid chromatography with fluorescence detection without adjusting the solution to alkaline. The analysis column was reversed-phase C8 column.

Simultaneous determination of 20 phthalate esters in oil-free food by UPLC/MS/MS.

A quantitative method was established for the determination of 20 phthalate esters (PAEs) in oil-free food by ultra-performance LC/MS/MS and was used to evaluate the PAEs of 111 oil-free samples from supermarkets in Hangzhou City. By quantification with the internal standard D4-bis(2-ethylexyl) phthalate, linearity ranges of the 20 PAEs were observed with correlation coefficients of 0.9990-0.

L-Proline as an efficient and reusable promoter for the synthesis of coumarins in ionic liquid.

The effect of L-proline as a promoter on the condensation reaction of salicylaldehyde or its derivatives with ethyl acetoacetate in neutral ionic liquid [emim]BF4 was studied. All reactions were carried out under mild reaction conditions and achieved high yields. Moreover, the ionic liquid containing L-proline could be recycled and reused for several times without noticeably decreasing in productivity.

Ab initio calculations on halogen-bonded complexes and comparison with density functional methods.

A systematic theoretical investigation on a series of dimeric complexes formed between some halocarbon molecules and electron donors has been carried out by employing both ab initio and density functional methods. Full geometry optimizations are performed at the Moller-Plesset second-order perturbation (MP2) level of theory with the Dunning's correlation-consistent basis set, aug-cc-pVDZ. Binding energies are extrapolated to the complete basis set (CBS) limit by means of two most commonly used extrapolation methods and the aug-cc-pVXZ (X = D, T, Q) basis sets series.

Fluorometric study on the interaction between lomefloxacin and bovine lactoferrin.

The binding of lomefloxacin to bovine lactoferrin (BLf) in a dilute aqueous solution was studied using fluorescence spectra. The binding constant (K) and the number of binding sites (n) were obtained by a fluorescence quenching method. The binding distance (r) and energy-transfer efficiency (E) between lomefloxacin and bovine lactoferrin were also obtained according to the mechanism of Foörster-type dipole-dipole nonradiative energy-transfer.

Binding interactions of pefloxacin mesylate with bovine lactoferrin and human serum albumin.

The binding of pefloxacin mesylate (PFLX) to bovine lactoferrin (BLf) and human serum albumin (HSA) in dilute aqueous solution was studied using fluorescence spectra and absorbance spectra. The binding constant K and the binding sites n were obtained by fluorescence quenching method. The binding distance r and energy-transfer efficiency E between pefloxacin mesylate and bovine lactoferrin as well as human serum albumin were also obtained according to the mechanism of Förster-type dipole-dipole nonradiative energy-transfer.