High Throughput Screening of 86 Kinds of Glucocorticoids in Cosmetics Using QuEChERS and Isotope Dilution-Liquid Chromatography Copuled to High Resolution Time-of-Flight Mass Spectrometry / 分析化学

A high throughput screening method based on QuEChERS purification and stable isotope dilution-liquid chromatography coupled to high resolution time-of-flight mass spectrometry was developed for the simultaneous rapid determination of 86 kinds of glucocorticoids (GCs) in cosmetics.The analytes were extracted by acetonitrile, and then the extracts were purified using an improved QuEChERS method.The chromatographic separation was performed on a novel multiple chromatographic retention mechanisms column of Poroshell 120 PFP (100 mm × 2.1 mm, 2.7 μm) with gradient elution using 0.2% (V/V) acetic acid and acetonitrile as mobile phase.The accurate mass database of parent ions and mass spectra library of fragment ions of 86 GCs were established under positive ionization mode with electrospray ionization source.Based on the method described above, the qualitative identifications of the 86 GCs were accomplished without the contrast of standard substances.The results demonstrated that the linear range of this method was from 2 μg/L to 200 μg/L with good correlation coefficients of R2>0.99.The average recoveries of the 86 GCs ranged from 66.2% to 112.8%, and the relative standard deviation (RSDs) was 4.6%-13.9% at three different spiked levels.The limit of detection (LOD) and quantification (LOQ) were 0.006-0.015 mg/kg and 0.02-0.05 mg/kg, respectively.The method is simple, efficient, reliable and accurate, and is suitable for high throughput screening of 86 GCs added illegally in cosmetics.

Rapid Screening of Carbamates Pesticide Residues in Vegetables by Electrospray Ionization Mass Spectrometry Based on Principle of Enzyme Inhibition / 分析化学

Arapidscreeningmethodforthedeterminationofcarbamatepesticides(CBPs)residuesin vegetables by measuring acetylcholinesterase ( AChE ) inhibition rate using electrospray ionization mass spectrometry ( ESI-MS ) has been established. After pretreatment by QuEChERS method, sample solution reacts with AChE using acetylthiocholine as substrate. AChE inhibition rate was calculated by determination of the conversion of substrate to product ( thiocholine) using ESI-MS. The temperature, time and concentration conditions of enzymatic reactions have been optimized. The relationship between the concentration of 10 kinds of common CBPs and AChE inhibition rate was researched. Matrix effects of real vegetables were studied. The limit of detection ( LOD) , which was measured by 3 times of enzyme inhibition rate of pesticide-free vegetable samples, was 0. 01-0. 05 mg/kg. The results showed that the method was better than the current national standard method of china for rapid screening of pesticide residues and fully meet the requirements of maximum residue limits( MRL) for pesticides in food of national food safety standard. False positive results were avoided effectively due to its good ability of resistance matrix interference. The reliability was proved by analyzing vegetables with liquid chromatography-tandem mass spectrometry. The method is simple, rapid, sensitive, reliable, and can be used for the rapid, high-throughput screening of CBPs in vegetables.

High Throughput Screening of Drug Multi Residues in Fish by Quadrupole-Time-of-Flight Mass Spectrometry / 分析化学

A high-throughput method for screening drug multi residues was developed by quadrupole-time-of-flight( Q-TOF) mass spectrometry together with QuEChERS sample preparation technique. It has been used for the determination of 57 drugs, such as tetracyclines ( TCs ) , sulfonamides ( SAs ) , quinolones ( QNs ) , triphenylmethanes (TPMs), estrogens (ETs), androgens (AGs) and glucocorticoids (GCs) in fish. The optimized pretreatment conditions were examined. The target compounds were extracted with acetonitrile under the condition of Na2 EDTA-Mcllvaine buffer, and the usage of clean-up reagents was 25 mg anhydrous magnesium sulfate, 12. 5 mg octadecylsilane and 6. 25 mg N-Propylethylenediamine sorbent for extracted solvent of each milliliter. The positive results acquired by this high-throughput method were confirmed by liquid chromatography-tandem mass spectrometry ( LC-MS/MS) . The detection limit for these 59 drugs was in the range of 0. 5-5. 3 μg/kg. The method is time-saving, convenient, effective and wide coverage. Its sensitivity can meet the requirement of the detection of drug residues in aquatic products.