A method for the simultaneous determination of robenidine, halofuginone, lasalocid, monensin, nigericin, salinomycin, narasin, and maduramicin residues in eggs by liquid chromatography–tandem mass spectrometry (LC–MS/MS) was developed. The sample preparation method used a combination of liquid–liquid extraction (LLE) and solid-phase extraction (SPE) technology to extract and purify these target compounds from eggs. The target compounds were separated by gradient elution using high-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography (UPLC). Tandem mass spectrometry was used to quantitatively and qualitatively analyze the target compounds via electrospray ionization (ESI⁺) and multiple reaction monitoring mode. The HPLC–MS/MS and UPLC–MS/MS methods were validated according to the requirements defined by the European Union and the Food and Drug Administration. The limits of detection and limits of quantification of the eight coccidiostats in eggs were 0.23–0.52 µg/kg and 0.82–1.73 µg/kg for HPLC–MS/MS, and 0.16-0.42 µg/kg and 0.81-1.25 µg/kg for UPLC–MS/MS, respectively. The eggs were spiked with four concentrations of the eight coccidiostats, and the HPLC–MS/MS and UPLC–MS/MS average recoveries were all higher than 71.69% and 72.26%, respectively. Compared with the HPLC–MS/MS method, utilizing UPLC–MS/MS had the advantages of low reagent consumption, a short detection time, and high recovery and precision. Finally, the HPLC–MS/MS and UPLC–MS/MS methods were successfully applied to detect eight coccidiostats in 40 eggs.

A simple, rapid and novel method for the detection of residues of thiamphenicol (TAP), florfenicol (FF) and its metabolite, florfenicol amine (FFA), in poultry eggs by ultra-performance liquid chromatography-fluorescence detection (UPLC-FLD) was developed. The samples were extracted with acetonitrile-ammonia (98:2, v/v) using accelerated solvent extraction (ASE) and purified by manual degreasing with acetonitrile-saturated n-hexane. The target compounds were separated on an ACQUITY UPLC^® BEH C₁₈ (2.1 mm × 100 mm, 1.7 μm) chromatographic column using a mobile phase composed of 0.005 mol/L NaH₂PO₄, 0.003 mol/L sodium lauryl sulfate and 0.05% trimethylamine, adjusted to pH 5.3 ± 0.1 by phosphoric acid and acetonitrile (64:36, v/v). The limits of detection (LODs) and limits of quantification (LOQs) of the three target compounds in poultry eggs were 1.8–4.9 µg/kg and 4.3–11.7 µg/kg, respectively. The recoveries of the three target compounds in poultry eggs were above 80.1% when the spiked concentrations of three phenicols were the LOQ, 0.5 maximum residue limit (MRL), 1.0 MRL and 2.0 MRL. The intraday relative standard deviations (RSDs) were less than 5.5%, and the interday RSDs were less than 6.6%. Finally, this new detection method was successfully applied to the quantitative analysis of TAP, FF and FFA in 150 commercial poultry eggs.