Comprehensive target analysis for 19 pyrethroids in tea and orange samples based on LC-ESI-QqQ-MS/MS and LC-ESI-Q-ToF/MS

Comparison of different fast gas chromatography - mass spectrometry techniques (Cold EI, MS/MS, and HRMS) for the analysis of pyrethroid insecticide residues in food

In the multiclass, multiresidue analysis of pesticides in food and environmental samples, pyrethroid insecticides are generally more difficult to analyze than other types of analytes. They do not ionize well by electrospray ionization, and although they are suitable for analysis by gas chromatography-mass spectrometry (GC-MS), selectivity using standard electron ionization (EI) in GC-MS is often insufficient because the molecular ion is rarely present. Many pyrethroids tend to have the same fragment ions in MS or high-resolution (HR)MS, and similar ion transitions in tandem MS/MS, leading to difficulties in distinguishing different pyrethroids from each other and chemical interferences in complex matrices. In this study, different forms of fast GC coupled with different types of MS detectors were compared for the analysis of up to 15 pyrethroids in barley extracts as a test case to assess which approach was the most advantageous. The three studied GC-MS techniques consisted of Cold EI using supersonic molecular beams in selected ion monitoring (SIM) mode with a single quadrupole instrument; triple quadrupole MS/MS; and HRMS using an orbital ion trap (orbitrap). A higher flow rate was used in Cold EI, and low pressure (LP) GC was employed in the MS/MS and orbitrap methods, to speed up the GC analyses (<10 min chromatograms in all cases). Each technique had some advantages over the others depending on specific pyrethroid analytes in the matrix. Nontargeted LPGC-orbitrap typically yielded the highest selectivity, but it rarely achieved the needed detectability to quantidentify the residues at 10 ng g-1. Cold EI-SIM and LPGC-MS/MS usually met the needed detection limits and generally achieved similar capabilities for the targeted pyrethroids.

Measuring the Residual Levels of Fenpyroximate and Its Z-Isomer in Citrus Using Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry and Assessing the Related Dietary Intake Risks

Fenpyroximate is an efficient, broad-spectrum phenoxypyrazole acaricide which is used for controlling various mites. In this study, we measured the levels of terminal fenpyroximate residues in citrus fruits, and estimated the dietary intake risks posed by fenpyroximate. To this end, a QuEChERS analytical method was used in combination with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to determine the residual levels of fenpyroximate and its Z-isomer (Z-fenpyroximate) in citrus fruits collected from 12 fields under good agricultural practices (GAPs). The average recoveries of fenpyroximate in whole fruits and citrus flesh were 104-110% and 92-109%, respectively, with corresponding RSDs of 1-4% and 1-3%. The average recoveries of Z-fenpyroximate were 104-113% and 90-91%, respectively, with RSDs of 1-2% in both cases. Each limit of quantification (LOQ) was 0.01 mg kg-1. Fifteen days after application with 56 mg kg-1, the terminal residues of fenpyroximate in whole fruits and citrus flesh were <0.010-0.18 mg kg-1 and <0.010-0.063 mg kg-1, respectively; the corresponding values for total fenpyroximate (the sum of fenpyroximate and Z-fenpyroximate) were <0.020-0.19 and <0.020-0.053 mg kg-1. The levels of terminal fenpyroximate residues in citrus fruit were less than the maximum residue limits (MRLs) specified in all the existing international standards. In addition, the risk quotients RQc and RQa were both less than 100%, indicating that the long-term and short-term dietary intake risks posed to Chinese consumers by fenpyroximate in citrus fruit are both acceptable after a 15-day harvest interval.

Characterization and quantification of ginsenosides from the root of Panax quinquefolius L. by integrating untargeted metabolites and targeted analysis using UPLC-Triple TOF-MS coupled with UFLC-ESI-MS/MS

The root of Panax quinquefolius L. (RPQ) is considered as an important functional food and rich in bioactive components, ginsenosides. To comprehensively characterize ginsenosides and evaluate the quality of RPQ from different sources, UPLC-Triple TOF-MS coupled with UFLC-ESI-MS/MS was applied to untargeted metabolites and targeted analysis for the first time. In untargeted metabolites analysis, a total of 225 ginsenosides were identified from RPQ using UPLC-Triple TOF-MS combined with SWATH data-independent strategy. Furthermore, the contents of 39 targeted ginsenoside markers in 14 RPQ samples were analyzed by a rapid and sensitive UFLC-ESI-MS/MS method. In addition, the results of chemometric analysis showed the quality of American RPQ was distinguished from that of Chinese RPQ according to the amount of targeted ginsenosides. This newly developed approach provides a powerful tool for enriching the diversity of saponins database and assessing the quality of RPQ, which can be further extended to other ginseng products and functional foods.