Multi-pesticide residue screening, identification, and quantification analysis in various fruits and vegetables by UHPLC-Q Exactive HRMS.

A general strategy for qualitative screening and quantitative analysis of 403 pesticides in various fruits and vegetables was developed using ultrahigh-performance liquid chromatography (UHPLC) in conjunction with a Thermo Q Exactive Focus high-resolution mass spectrometer, relying on an executable compound database comprised of the exacted mass of precursor ions, retention times, and fragment ions. Taking advantage of the powerful separation capacity of UHPLC, an Orbitrap analyzer with high sensitivity in full scan mode and elevated mass resolution of product ions in the MS/MS mode, eight pairs of isomers and fifty-seven groups of isobaric compounds were selectively identified. The method was then systematically assessed and validated for eight fruits and vegetables, in terms of screening detection limit (SDL), matrix effects, recovery, and precision over 400 pesticides. The results showed that the SDLs of 68.0-84.4% for the pesticides were less than or equal to 10 µg kg-1 in the representative matrices, recoveries in the range of 60-120% accounting for 48.6-84.4% of all the targets at three lower fortified levels of 5, 20, and 50 µg kg-1 with a precision of less than 20% while the range of overall average recoveries for the majority of the pesticides were from 82.4% to 105.1% in the as-selected matrices with RSDs between 3.9% and 7.7%. Using this method, screening data from a survey of pesticide residues in 68 practical samples across 32 different matrix types provides scientific data for the inspection and supervision of pesticide residue safety of fruits and vegetables.

Determination of multiclass contaminants in chilli powder based on magnetic multiwalled carbon nanotubes and UPLC-QTOF/MS.

A multiclass analysis approach was developed using magnetic multiwalled carbon nanotubes sorbents and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) for the rapid screening and simultaneous determination of 216 contaminants including 15 mycotoxins, 9 synthetic colourants, and 192 pesticides in chilli powder. The sample preparation process was optimized. The optimal preparation procedure utilized NaCl and NaAc as the salting-out agents, and Fe3O4-MWCNTs as the sorbents, resulting in reduced chemical consumption, improved cleaning performance, and facilitated high-throughput analysis. The proposed method was validated, and satisfactory parameters were obtained. Approximately 85.6% of the target analytes exhibited a weak matrix effect, with the matrix effects falling within the range of 0.8 âˆ¼ 1.2. The method demonstrated acceptable recoveries of the analytes, falling within the range of 62.14%∼119.76% at three fortified levels with relative standard deviations (RSDs) of less than 20%. Additionally, the method's limit of quantification (LOQ) ranged from ranged from 0.50 µg·kg-1 to 49.56 µg·kg-1. The method was further applied for analysis of 27 chilli powder samples, demonstrating its potential for screening and quantification of multiclass contaminants for spices.

UPLC-Q-TOF/MS-based metabolomic analysis reveals the effects of asomate on the citrus fruit.

The regulation of the sugar-acid ratio is of great significance to the improvement of citrus fruit quality. The citric acid level in fruit is influenced by many factors. Among them, cultivar selection and production practices are the most important strategies under the grower's control. In recent years, an arsenic-containing preparation called "Tianmisu", with the main ingredient of asomate, has occasionally been reported to be used in citrus cultivation to improve the sweetness of fruits. In order to reveal the effects of the pesticide on citrus fruits, 'Harumi' tangor was treated with "Tianmisu", and the impact of this pesticide on fruit quality and metabolites was investigated through UPLC-Q-TOF/MS-based metabolomic analysis. Compared with the control, the concentration of titratable acidity, in particular citric acid, in the pulp of 'Harumi' tangor treated with the pesticide, was significantly reduced by 60.5%. The differences in metabolites between the pesticide-treated samples and the control were illustrated by Principal Component Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLS-DA). The PLS-DA analysis demonstrated a clear discrimination, with R2Y and Q2 values of 0.982 and 0.933 in the positive mode and 0.984 and 0.900 in the negative mode, respectively. A total of 155 compounds were identified, and 63 characteristic components were screened out from the pesticide-treated samples compared to the control. Aside from the upregulation observed for a few metabolites, the majority of the compounds, including citric acid and various lipids, were down-regulated in the treated citrus fruits compared to the control. This study can serve as a basis for understanding the regulatory mechanism of organic acids in citrus and will be helpful in developing different strategies to improve citrus quality.