QuEChERS Liquid Chromatography-tandem Mass Spectrometry Research Articles

Determination of 105 pesticide residues in vegetables by QuEChERS-liquid chromatography-tandem mass spectrometry

After optimization of the QuEChERS pretreatment method, combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology, a multi-residue determination method was established for 105 typical insecticides, bactericides, herbicides, and plant growth regulators in vegetables. The target compounds were extracted by acetonitrile, purified with 150 mg primary secondary amine (PSA), 150 mg EC-C18, and 30 mg graphitized carbon black (GCB) adsorbents. The standard curves of 105 target compounds were linear in the concentration range of 0.010-0.200 mg/L, with correlation coefficients (r)>0.99. The limit of quantification was 0.010 mg/kg, the recoveries were between 68.2% and 108% at three spiked levels, and the RSDs of the method were between 1.02% and 11.8%. The method is suitable for the rapid determination of the common pesticides in vegetables owing to its advantages of rapidity, simplicity, and better purification.

Simultaneous determination of pyraclostrobin and thiophanate-methyl and its metabolite carbendazim residues in soil and citrus by QuEChERS-liquid chromatography- tandem mass spectrometry

A QuEChERS-liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of pyraclostrobin, thiophanate-methyl and its metabolite carbendazim in soil and citrus. The samples were extracted with methanol or acetonitrile, purified by primary secondary amine (PSA), then separated by LC, detected in multiple reaction monitoring (MRM) mass spectrometry mode via positive electrospray ionization. The analytes were quantified by matrix-matched standard solutions with external standard method. The limits of quantification (LOQs) of pyraclostrobin, thiophanate-methyl and carbendazim in different matrices were 5.8-7.0 μg/kg, 9.3-14.1 μg/kg and 2.1-2.6 μg/kg, respectively. For all the samples, the spiked recoveries ranged from 75.48% to 109.18%, and the relative standard deviations (RSDs) were 0.60%-5.11% (n=5). The method is quick, easy, effective, sensitive and accurate. The matrix-matched calibration solutions can efficiently compensate matrix effects of the pyraclostrobin, thiophanate-methyl and carbendazim in LC-MS/MS analysis. The established method can be applied to the residue analysis of the real samples of soil, citrus peel, citrus pulp and citrus fruits.

Determination of 16 pesticide residues in fruits and vegetables by QuEChERS-liquid chromatography-tandem mass spectrometry

A sensitive and convenient liquid chromatography-tandem mass spectrometric method was developed for the determination of 16 pesticides such as imidacloprid, prochloraz, difenoconazole, azoxystrobin, and thiamethoxam in fruits and vegetables. After compared with methanol and acetone-cyclohexane (1:2, v/v), acetonitrile was chosen as the extraction solvent. The samples were extracted by acetonitrile in high-speed homogenization. The extraction solution was cleaned up by liquid-liquid extraction, and the supernatant was collected. In this work, QuEChERS exhibited much higher efficiency than Carbon-NH2 solid-phase extraction in purification. The pigments and organic acids were removed by purge line (150 mg primary secondary amine (PSA) sorbent and 900 mg absolute magnesium sulfate), leading to the decrease of the background interferences. The average recoveries of the 16 pesticides were almost in the range of 75%-111% at the three spiked levels, and the relative standard deviations were less than 16%. The qualitative analysis and quantitative analysis were investigated by LC-MS/MS and matrix-matched calibration curves. The results showed that the method of QuEChERS combined with LC-MS/MS is rapid, accurate and sensitive for the determination of the 16 pesticide residues in fruits and vegetables.

Determination of 30 carbamate pesticide residues in vegetative foods by QuEChERS-liquid chromatography-tandem mass spectrometry

Via the classification of vegetative foods in British Standard EN 15662, six representative food matrices were chosen in the current study. The QuEChERS method for each matrix was optimized. The 30 carbamate pesticide residues in the samples after pretreatment were determined by liquid chromatography-tandem mass spectrometry in positive ionization mode. According to the experimental results, the linear ranges were 1-100 µg/kg for aldicarb sulfone and 2-100 µg/kg for the others. The recoveries at three spiked levels of 5, 20 and 100 µg/kg in the six representative matrices were between 56.13% and 127.6%, with the RSDs between 0.47% and 16%. The limits of quantification (S/N-10) were in the range of 0.041-1.9 kg/kg. In conclusion, this method provides a sensitive and efficient way suitable for the analysis of the 30 carbamate pesticide residues in vegetative foods.

Determination of Residual Flubendiamide in the Cabbage by QuEChERS-Liquid Chromatography–Tandem Mass Spectrometry

Flubendiamide, which belongs to the new chemical class of phthalic acid diamides, is widely used against lepidopteron pests in a variety of vegetable and rice pests. It provides superior plant protection against a broad range of economically important lepidopterous pests, including Spodoptera exigua and Plutella xylostella. A determination method of flubendiamide in the cabbage was established in this paper. Flubendiamide in the cabbage was extracted with acetonitrile and ultrasonic extraction, and was purified by QuEChERS and analyzed by LC-MS/MS (liquid chromatography-tandem mass spectrometry). The results indicated that the average recovery of flubendiamide in the cabbage was 81.27%-91.45%, the coefficient of variation was 1.79%-4.81%, and the lowest detection concentration was 0.3 μg/kg. The extraction of flubendiamide from the cabbage and its analysis was in accordance with the pesticide residue criterion, i.e., simple, rapid, accurate, reproducible, stable, separatory, and convenient. It identifies and quantifies trace-level flubendiamide residues in the cabbage extracts using LC-MS/MS in the ESI negative mode coupled with the QuEChERS method.