Abstract:

The consumption of agricultural products has increased in recent years owing to abundant production and improved living standards. Veterinary drugs are highly commercialized and widely used in animal husbandry to ensure animal health and production performance. Moreover， pesticides can become enriched during animal breeding， resulting in animal-derived food pollution through foraging， drinking， and environmental disinfection that can potentially damage human health. Consequently， food-safety issues associated with pesticide and veterinary-drug residues have attracted considerable attention. However， few reports on the multi-residue analysis of livestock and poultry meat using ultra performance liquid chromatography-quadrupole time of flight mass spectrometry （UPLC-Q-TOF/MS） have been published. Therefore， developing high-throughput and efficient screening methods for monitoring various illegal and/or restricted drugs in animal-derived foods is imperative. In this study， we developed a protocol for simultaneously examining seven pesticide and veterinary-drug types that uses an accurate mass-spectral library. UPLC-Q-TOF/MS was then employed to screen 111 such compounds， including quinolones， macrolides， cephalosporins， and antiviral drugs. The developed protocol was subsequently used to establish a method for quantitatively analyzing more than 90 compounds in livestock and poultry meat. The formula， theoretical exact mass， experimental exact mass， and retention time of each analyte were recorded and used for identification purposes. The main factors affecting the response and sensitivity of the method， such as the LC separation conditions （chromatographic column and mobile phases） and MS parameters， were optimized during instrumental analysis. Pork and chicken samples were extracted with an 80% acetonitrile aqueous solution， after which the supernatant was purified using an Oasis PRiME HLB solid-phase extraction column. The 111 target analytes were separated on a Waters HSS T3 analytical chromatographic column （100 mm×2.1 mm， 1.8 μm） after being blown with nitrogen and redissolved， with gradient elution performed using mobile phases composed of 0.1% formic acid aqueous solution and methanol. The analysis process included a flow rate of 0.4 mL/min， a column temperature of 40 ℃， and an injection volume of 5 μL， with positive electrospray ionization （ESI） and time of flight mass spectrometry full scan information-dependent acquisition-product ion （TOF MS-IDA-Product Ion） scanning modes used. The method was validated in terms of linearity， limits of screening and quantification （SDLs and LOQs， respectively）， matrix effects， accuracy， and precision. Quantification was performed using matrix-matched external-standard calibration. All target compounds exhibited good linearities in their corresponding concentration ranges， with all correlation coefficients （r²） above 0.99. The SDLs of all analytes were in the range of 0.5-10 μg/kg， and the proportion of LOQs within the range of 0.5-10 μg/kg were 88.3% and 86.5%， respectively. The compounds quantified in pork and chicken exhibited recoveries of between 60.2% and 100.2%， and 61.1% and 116.7%， respectively， at spiked levels of LOQ， 2×LOQ and 10×LOQ， with relative standard deviations （RSDs） ranging from 1.1% to 13.9% and 1.0% to 14.1%， respectively. Simulated positive samples and commercial livestock and poultry meat samples were screened using an in-house-constructed mass spectrometry database. Commercial samples were screened while enrofloxacin was detected in two pork samples and tilmicosin was detected in one chicken sample， with content in the range of 4.94-29.1 μg/kg. The method developed in this study is advantageous because it involves simple sample processing and is less time consuming than existing methods； consequently， it is suitable for the rapid and high-throughput screening of pesticides and veterinary residues in livestock and poultry meat.

Key words: ultra performance liquid chromatography-quadrupole-time of flight mass spectrometry （UPLC-Q-TOF/MS）, livestock and poultry meat, pesticides and veterinary drugs, rapid screening, multi-residue analysis