[Determination of 14 pesticide residues in crucian carp using on-line gel permeation chromatography-multi gas chromatography/mass spectrometry].

A new method was developed for the determination of pesticide residues in crucian carp using on-line gel permeation chromatography-multi gas chromatography/mass spectrometry (GPC-MDGC/MS). The pesticide residues were extracted with cyclohexane-ethyl acetate (1:1, v/v) for twice. After being frozen, the extract was filtered by 0.22 microm member, and then cleaned up and analyzed by online GPC-MDGC/MS. The pesticides were selectively transferred from the 1st column to the 2nd column by means of heart cutting. As a result, selective transfers of some pesticides from the first to the second dimension were at times essential to avoid overlapping. The selected separation conditions from the study with standards were applied to crucian carp spiked with some pesticide standards. The performance of this method was examined by recovery, linearity and precision. Inter-standard quantitative method was used for calculation. Good linear relationship was achieved in the range of 0.01-0.9 mg/L for the 14 pesticides with correlation coefficients above 0.99. The recoveries of the method ranged from 83.0% to 112.9% with the relative standard deviations (RSDs) among 3.2%-12.0% at 3 spiked levels of 0.01, 0.05 and 0.1 mg/kg. This is a simple, rapid method for the analysis of multiple pesticide residues in crucian carp with high accuracy and sensitivity. The results prove that the employment of a multidimensional analysis technique permits to avoid interferences of the analytes with matrix components.

Simultaneous determination of 44 pesticides in tobacco by UPLC/MS/MS and a modified QuEChERS procedure.

A novel, simple, and rapid method for determination of the residues of 44 commonly used pesticides in tobacco was developed based on modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) procedures. The pesticides were extracted with acetonitrile and purified on a mixed sorbents column of primary secondary amine, C18, and graphitized carbon black. Quantitative determination of all pesticides was performed by ultra-performance LC/MS/MS in the positive or negative ionization mode by a single run due to the fast polarity switching capability of the mass spectrometer. Two precursor-product ion transitions were monitored for each compound in the multiple reaction monitoring mode. Quantification was carried out using matrix-matched standard calibration. The method has been validated by various tobacco cultivars, such as Burley, Oriental, and Virginia from different countries. Recoveries of the proposed method for spiked samples ranged from 71.1 to 109.8%, and RSD values were below 10%. The LOQ values were are all below the guidance residue levels proposed by the Agrochemical Advisory Committee of Cooperation Center for Scientific Research Relative to Tobacco. This method is valuable for measurement of pesticide residues in tobacco for QC and monitoring.

[Determination of 14 mycotoxins in Chinese herbs by liquid chromatography-tandem mass spectrometry with immunoaffinity purification].

A method was developed for the determination of 14 mycotoxins, aflatoxins, T-2, HT-2, fumonisins, ochratoxin A, zearalenone, etc. in Chinese herbs by liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). The sample was extracted with phosphate buffer solution (PBS) and methanol in turn, and then purified by a high selective multi-functional immunoaffinity column. The column was washed by PBS (containing 0.1% Twain) and water, and then eluted by methanol. The eluate was dried under nitrogen, dissolved in methanol-10 mmol/L NH4Ac (40 : 60, v/v) solution. The mycotoxins were separated on a Waters Xterra C18 MS column (100 mm x 2.1 mm, 3.5 microm) and detected by MS/MS. The limits of quantification (LOQs) of the 14 mycotoxins were from 1.0 to 5.0 microg/kg. The average recoveries of the 14 mycotoxins spiked in Chinese herbs (Ginseng, Campanulaceae, Radix and Ophiopogonis) ranged from 71.9% to 99.7% at the three spiked levels of 1.0, 5.0, 10.0 microg/kg, and the relative standard deviations (RSDs, n = 6) were between 4.8% and 15.8%. The method is rapid, sensitive and accurate, and suitable for the determination of the 14 mycotoxins in Chinese medicines. The quantification limits of aflatoxins can meet the domestic and foreign requirements.