High-Throughput Screening and Confirmation of 22 Banned Veterinary Drugs in Feedstuffs Using LC-MS/MS and High-Resolution Orbitrap Mass Spectrometry

A new analytical strategy based on liquid chromatography–tandem mass spectrometry (LC-MS/MS) combined with accurate mass high-resolution Orbitrap mass spectrometry (HR-Orbitrap MS) was performed for high-throughput screening, confirmation, and quantification of 22 banned or unauthorized veterinary drugs in feedstuffs according to Bulletin 235 of the Ministry of Agriculture, China. Feed samples were extracted with acidified acetonitrile, followed by cleanup using solid-phase extraction cartridge. The extracts were first screened by LC-MS/MS in a single selected reaction monitoring mode. The suspected positive samples were subjected to a specific pretreatment for confirmation and quantification of analyte of interest with LC-MS/MS and HR-Orbitrap MS. Mean recoveries for all target analytes (except for carbofuran and chlordimeform, which were about 35 and 45%, respectively) ranged from 52.2 to 90.4%, and the relative standard deviations were <15% except for 20% for carbofuran. The decision limits (CCαs) for target analytes in formulated feed were between 2.6 and 23 μg/kg, and the detection capabilities (CCβs) were between 4.2 and 34 μg/kg. The method was successfully applied to screening of real samples obtained from local feed markets and confirmation of the suspected target analytes. It provides a high-throughput, sensitive, and reliable screening, identification, and quantification of banned veterinary drugs in routine monitoring programs of feedstuffs

High-Throughput Screening and Confirmation of 22 Banned Veterinary Drugs in Feedstuffs Using LC-MS/MS and High-Resolution Orbitrap Mass Spectrometry

A new analytical strategy based on liquid chromatography–tandem mass spectrometry (LC-MS/MS) combined with accurate mass high-resolution Orbitrap mass spectrometry (HR-Orbitrap MS) was performed for high-throughput screening, confirmation, and quantification of 22 banned or unauthorized veterinary drugs in feedstuffs according to Bulletin 235 of the Ministry of Agriculture, China. Feed samples were extracted with acidified acetonitrile, followed by cleanup using solid-phase extraction cartridge. The extracts were first screened by LC-MS/MS in a single selected reaction monitoring mode. The suspected positive samples were subjected to a specific pretreatment for confirmation and quantification of analyte of interest with LC-MS/MS and HR-Orbitrap MS. Mean recoveries for all target analytes (except for carbofuran and chlordimeform, which were about 35 and 45%, respectively) ranged from 52.2 to 90.4%, and the relative standard deviations were <15% except for 20% for carbofuran. The decision limits (CCαs) for target analytes in formulated feed were between 2.6 and 23 μg/kg, and the detection capabilities (CCβs) were between 4.2 and 34 μg/kg. The method was successfully applied to screening of real samples obtained from local feed markets and confirmation of the suspected target analytes. It provides a high-throughput, sensitive, and reliable screening, identification, and quantification of banned veterinary drugs in routine monitoring programs of feedstuffs

Oxidation-Sulfidation Approach for Vertically Growing MoS₂ Nanofilms Catalysts on Molybdenum Foils as Efficient HER Catalysts

Molybdenum disulfide (MoS₂) has emerged as a promising electrocatalyst for hydrogen evolution reaction (HER). However, the performance of the catalyst suffers from the scarce active sites and poor electrical conductivity. Here we grow vertical MoS₂ films on Mo foils to achieve highly catalytic active sites and enhanced electrical conductivity for facilitating high efficient HER catalysis. The ultrathin nanofilm with a thickness of around 4 nm on molybdenum foils is grown by a two-step method: (1) the molybdenum oxide (MoO₂) nanofilm is achieved by oxidizing the surface of the Mo foil under a low pressure condition and (2) a MoS₂ nanofilm is obtained by sulfurizing the MoO₂ nanofilm in sulfur vapor at 700 °C within 1 min. Furthermore, the vertically aligned MoS₂ nanofilm on Mo foils exhibit excellent stability in acidic solution and the electrochemical measurements show an onset overpotential of as low as 18 mV and a small Tafel slope of 55 mV/dec. The excellent HER catalysis originates from the synergistic effect of the dense catalytic active sites at the vertical MoS₂ surface and superior electron transport along the Mo foil. This study opens a novel avenue for the development of earth-abundant, low-cost electrocatalysts with high HER activities