Development and Validation of a Multiresidue Method for the Determination of Pesticides in Dry Samples (Rice and Wheat Flour) Using Liquid Chromatography/Triple Quadrupole Tandem Mass Spectrometry

Abstract

A rapid and sensitive multiresidue method was developed and validated for the determination of around 100 pesticides in dry samples (rice and wheat flour) by ultra-performance LC coupled to a triple quadrupole mass analyzer working in tandem mode (UPLC/QqQ-MS/MS). The sample preparation step was optimized for both matrixes. Pesticides were extracted from rice samples using aqueous ethyl acetate, while aqueous acetonitrile extraction [modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method] was used for wheat flour matrixes. In both cases the extracts were then cleaned up by dispersive solid phase extraction with MgSO4 and primary secondary amine+C18 sorbents. A further cleanup step with Florisil was necessary to remove fat in wheat flour. The method was validated at two concentration levels (3.6 and 40 μg/kg for most compounds), obtaining recoveries ranging from 70 to 120%, intraday and interday precision values≤20% expressed as RSDs, and expanded uncertainty values≤50%. The LOQ values ranged between 3.6 and 20 μg/kg, although it was set at 3.6 μg/kg for the majority of the pesticides. The method was applied to the analysis of 20 real samples, and no pesticides were detected.

Optimization and validation of a QuEChERS-based method for the simultaneous environmental monitoring of 218 pesticide residues in clay loam soil

“…The original QuEChERS method was developed for fruits and vegetables, which are samples with high water content (> 70%). Therefore, when processing dry samples with QuEChERS it is common to add some amount of water (Grande-Martinez et al, 2015), and in fact, in soil samples it has been described that the addition of water could make the pores more accessible to the extraction solvent (Pinto et al, 2010). Thus, adding water to the soil samples was the next step in the optimization process.…”

Practical approach to develop a multi‐group screening method for detection of mycotoxins, pesticides and veterinary drugs in food

“…In rabbits, enrofloxacin was found together with ciprofloxacin, being this latter its metabolite. Mycotoxin residues (mainly deoxynivalenol and 3‐acetyldeoxynivalenol) were detected in 10 wheat flour samples out of 30 with confirmed concentrations frequently above the STCs 30 . On the other hand, pesticides were never found.…”

“…However, it must be underlined that in the negative (unspiked) samples, the presence of some analyte was detected and always confirmed, frequently at concentrations lower than STCs (Table 2). Due to the excessive effort, that is, the application of various confirmatory methods for each class of compounds such as antibiotics, 19 benzimidazoles, 26 avermectins, 27 nitroimidazoles, 28 steroids, 29 pesticides 30 or mycotoxins, 31 the 40 muscles and the 30 wheat flours selected for the validation study were not previously analysed to ascertain whether they were actually negative. Therefore, these samples should be called ‘not spiked’ instead of ‘negative’.…”

“…Suspect screening samples and results of the relevant confirmatory analysis concentrations frequently above the STCs 30. On the other hand, pesticides were never found.…”