Analysis of 118 pesticides in tobacco after extraction with the modified QuEChRS method by LC-MS-MS.

A liquid chromatography-tandem quadrupole mass spectrometry (LC-MS-MS) multi-residue method for the simultaneous target analysis of a wide range of pesticides in tobacco has been developed. Gradient elution has been used in conjunction with positive mode electrospray ionization tandem mass spectrometry to detect up to 118 pesticides in tobacco. The recoveries obtained for each pesticide ranged between 70 and 118% at two spiked concentration levels. Good linear relationships were observed with correlation coefficients r(2) > 0.992 for all analytes. The established method was successfully applied to the determination of pesticide residues in real tobacco samples in order to validate the suitability for routine analysis.

Determination of chlorinated phenoxy acid herbicides in tobacco by modified quechERS extraction and high-performance liquid chromatography/tandem mass spectrometry.

A new method for determination of phenoxy acid herbicide residues in tobacco based on the use of liquid extraction/partition and dispersive SPE followed by HPLC/electrospray ionization-MS/MS is reported. Formic acid (2%, v/v) in acetonitrile as the extraction solvent and inclusion of citrate buffer helped partitioning of all analytes into the acetonitrile phase. Quantitative analysis was done in the multiple-reaction monitoring mode using two combinations of selected precursor ion and product ion transition for each compound. The recoveries obtained for each pesticide ranged between 85 and 110% at two spike concentration levels. Good linear relationships were observed, with the correlation coefficient (r2) >0.998 for all analytes. The method is simple, efficient, and sensitive, and each of its performance characteristics meets the requirements for determination of phenoxy acid herbicide residues in tobacco.

Development and validation of a method for the determination of 159 pesticide residues in tobacco by gas chromatography-tandem mass spectrometry.

A multiresidue gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed for the analysis of 159 multiclass pesticides in tobacco. A modified QuEChERS sample preparation technique, based on acetonitrile extraction and toluene dilution, followed by dispersive solid-phase extraction (d-SPE) cleanup using primary-secondary amine (PSA) and octadecyl (C18) sorbents, was used for sample treatment. Key performance parameters investigated were linearity, recovery, relative standard deviation (RSD), limit of detection, and limit of quantitation. With the exception of chinomethionate and folpet, recoveries for pesticides ranged from 69 to 141%, and the RSDs ranged from 2 to 27%. The validated method was applied to the analysis of 118 real samples, and positive results were obtained for 116 samples, with 25 different pesticides being detected.

[Comparison of three different QuEChERS sample treatment methods in the analysis of more than one hundred pesticide residues in tobacco by gas chromatography-tandem mass spectrometry].

With a combination of QuEChERS method and gas chromatography-tandem mass spectrometry (GC-MS/MS) technique, three sample treatment methods (solvent exchange method, toluene dilution method, hexane liquid-liquid extraction method) were established to analyse more than one hundred pesticide residues in tobacco. The 155 pesticide analytes contained 58 organophosphorus, 28 organochlorine, 10 pyrethroids, 10 acyl amide, 11 carbamate, 7 dinitroaniline and 31 other family pesticides. Comparison of the three treatment methods was investigated on performances including matrix effect, co-extracted matrix, peak interference, recovery and the limit of quantification (LOQ). The hexane liquid-liquid extraction method gave the cleanest extract but poorer recovery; the solvent exchange and toluene dilution method could guarantee recoveries in the range of 70% and 120% for most of the 155 pesticides. We found that organophosphorus, acyl amide and carbamate pesticides exhibited relative strong matrix effects compared with organochlorine and pyrethroid pesticides. Toluene dilution method was recommended to analyse organophosphorus pesticides, and hexane liquid-liquid extraction (LLE) method was recommended to analyse organochlorine and pyrethroid pesticides.

[Determination of 132 pesticide residues in tobacco by gas chromatography-tandem mass spectrometry].

A simple method for the determination of 132 pesticide residues in tobacco by gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS) was established. The influences of different extraction solvents, different buffer systems and different purifying agents on the recoveries of pesticides were investigated. The tobacco sample was extracted with acetonitrile, then cleaned up by the mixed sorbents of primary secondary amine (PSA) and octadecylsilane (C18E). After dried by nitrogen, the extract residue was reconstituted with n-hexane-acetone (9:1, v/v). GC-MS/MS in multi-reaction monitoring (MRM) mode was used as the detection method and triphenyl phosphate (TPP) as the internal standard. All of the 132 pesticides had good linear relationships (r2 > 0.99) between 20 microg/kg and 2 000 microg/kg. At the three spiked levels of 50, 200 and 500 microg/kg in the tobacco extract, the average recoveries of all the pesticides were in the range of 68.10% to 123.15% except for mirex and hexachlorobenzene; moreover, the relative standard deviations (RSDs) of them were between 1.79% and 19.88%. We participated in the CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco) 2012's co-experiment. The results of our method and the existed standard methods had good consistency. The accurate, reliable and sensitive method can be applied to the determination of the 132 pesticide residues in tobacco for rapid screening and quantitative analysis.