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A simple and efficient LC/ESI/MS/MS method was developed to determine 18 (fluoro)quinolone (QNs) residues in milk, chicken, pork, fish and shrimp. This method is capable of screening and confirming the presence of 12 amphoteric QNs (marbofloxacin, norfloxacin, enrofloxacin, ciprofloxacin, desethylene ciprofloxacin, lomefloxacin, danofloxacin, sarfloxacin, difloxacin, ofloxacin, orbifloxacin and enoxacin) and 6 acidic QNs (oxolinic acid, nalidixic acid, flumequine, cinoxacin, piromidic acid and pipemidic acid). The drugs were extracted from matrix with acetonitrile containing 1% formic acid, diluted in 10% acetonitrile and defatted by extraction with hexane. The LC separation was conducted on an XDB C-8 (150 mm × 4.6 mm, 5 μm) column with gradient elution of 20 mM ammonium formate in 0.1% formic acid-acetonitrile as the mobile phase. Mass spectrum acquisition was completed in the positive ion mode by applying multiple reaction mode (MRM). The decision limit (CCα) and detection capability (CCβ), stated in the Decision No. 2002/657/EC and the ISO standard No.11843, have been calculated in the case of nonauthorized substance. The values of CCα ranged from 0.18 to 0.68 ng/g and CCβ ranged from 0.24 to 0.96 ng/g under specified conditions. [ABSTRACT FROM AUTHOR]

A simple and efficient multiresidue method was developed for determining 11 quinolones (QNs; marbofloxacin, norfioxacin, ciprofloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin, difloxacin, oxolinic acid, nalidixic acid and flumequine) in chicken, pork, fish and shrimp. The analytes were extracted with 0.3% metaphosphoric acid and acetonitrile (1:1, v/v), followed by a HLB cartridge clean-up procedure. The HPLC separation was carried out on a symmetry column C-18 (250 mm × 4.5 mm i.d., 5 μm) with linear gradient elution of 0.1% formic acid and acetonitrile as mobile phase and programmable fluorescence detection. The method was validated by spiking blank animals tissues at three different levels (25, 50 and 250 ng/g; except 6.25, 12.5 and 62.5 ng/g for DAN) while the linearity, detection limit, quantification limit, precision and accuracy were checked. Mean recoveries of II QNs from edible animal tissues were 71.7-105.3%. The limits of quantification in different muscle tissues ranged from 5.0 to 28.0 ng/g. The results showed this method was simple, rapid, sensitive and suitable for routine tests. [ABSTRACT FROM AUTHOR]

A precise and reliable analytical method to measure trace levels of sulfamonomethoxine (SMM) and N4-acetyl metabolite in tilapia samples using liquid chromatography-tandem mass spectrometry was developed. Optimized chromatographic separation was performed on C18 reversed-phase columns using gradient elution with methanol and 5 mmol/L of an ammonium acetate aqueous solution (adjusted to pH 3.5 using formic acid). This study investigated the pharmacokinetic properties and tissue distribution of SMM and its major metabolite N4-acetyl sulfamonomethoxine (AC-SMM) in tilapia after a single dose of 100 mg kg-1 body weight of orally administered SMM. Blood and tissues were collected between 0.5 and 192 h with 14 total sampling time points. SMM was rapidly absorbed, and extensively distributed in the bile and liver through systemic circulation. Enterohepatic circulation of SMM was observed in the tilapia body. Acetylation percentages were 45% (blood), 90% (liver), 62% (kidney), 98% (bile), and 52% (muscle). High concentrations of AC-SMM accumulated in the tilapia bile. At 192 h, AC-SMM concentration in the bile remained at 4710 mg kg-1. The ke value of AC-SMM (0.015 h-1) in the blood was lower than that of SMM (0.032 h-1). This study demonstrated effective residue monitoring and determined the pharmacokinetic properties of SMM and AC-SMM in tilapia. [ABSTRACT FROM AUTHOR]

A LC-MS/MS method was validated for the simultaneous quantification of 4 quinolones (oxolinic acid, enrofloxacine, ciprofloxacine, norfloxacine) and 4 sulfonamides (sulfamethoxypyridazine, sulfadoxine, sulfadimidine, sulfamerazine) on fish muscle following the European Union's (EU) criteria for the analysis of veterinary drug residues in foods. One gram of sample was extracted by acidic acetonitrile (0.5 mL of 0.1% formic acid in 7 mL of ACN), followed by LC-MS/MS analysis using an electrospray ionization interface. Typical recoveries of the 4 quinolones in the fish tissues ranged from 85 to 104%. While those of the sulfonamides ranged from 75 to 94% at the fortification level of 5.0 µg/kg. The decision limits (CCα) and detection capabilities (CCβ) of the quinolones were 1.35 to 2.10 µg/kg and 1.67 to 2.75 µg/kg, respectively. Meanwhile, the CCα and CCβ of the sulfonamides ranged from 1.62 µg/kg to 2.53µg/kg and 2.01µg/kg to 3.13 µg/kg, respectively. [ABSTRACT FROM AUTHOR]

A method validated based on the European Union (EU) regulations for determining the presence of furazolidone, furaltadone, nitrofurazone, nitrofurantoin and their corresponding metabolites AOZ, AMOZ, SC and AH in fish muscle was developed. Samples were acid-hydrolyzed, treated with 2-nitrobenzaldehyde and extracted with ethyl acetate. The extracts were dried in a N2 stream and redissolved in methanol:water (50:50, v/v). Analysis was performed by LC/ESI/MS/MS. This developed method carried limits of quantification lower than 10 μg/kg for the nitrofurans and 1.0 μg/kg for the metabolites. It was observed that the decision limit (CCβ) ranged from 2.93 to 5.01 μg/kg for the nitrofurans and 0.19 to 0.43 μg/kg for the metabolites. The detection capability (CCβ) was between 3.62 and 6.20 μg/kg for the nitrofurans and between 0.23 and 0.54 μg/kg for the metabolites. The linear calibration curve parameters in the fortified fish muscle were between 1.0-100.0 μg/kg and 0.1-10.0 μg/kg for the nitrofurans and metabolites, respectively. [ABSTRACT FROM AUTHOR]

In this study, a method for determination of cholesterol and four phytosterols by gas chromatography coupled with electron impact ionization mode-tandem mass spectrometry without derivatization in general food was developed. The sample was saponified with 7.5% KOH in methanol. After heating on hot plate and reflux for 60 minutes, the saponified portion was extracted with n-hexane/petroleum ether (50:50, v/v). The extracts were evaporated with rotary evaporator and then redissolved with tetrahydrofuran. The tetrahydrofuran layer was transferred into an injection vial and analyzed by gas chromatography on a 30 m VF-5 column. Limit of quantification was 2 mg/kg. Recoveries of cholesterol and four phytosterols from general food were between 91% and 100%. [ABSTRACT FROM AUTHOR]

A confirmatory and quantitative method based on liquid chromatographyetandem mass spectrometry (LC/MS/MS) has been developed for the determination of low-level residues of three antibiotic dyes and two metabolites in fish muscle and feed. The target compounds include methylene blue (MB), crystal violet (CV), leucocrystal violet (LCV), malachite green (MG), and leucomalachite green (LMG). The procedures involve solvent extraction by 50% McIlvaine’s buffer with acetonitrile, followed by solid phase extraction (SPE) with an MCX cartridge. High performance liquid chromatography (HPLC) and positive electrospray ionization (ESI) MS with multiple reaction monitoring of two transition reactions was applied for each compound. The detected ion ratios of MB, CV, LCV, MG, and LMG were 11.8, 34.9, 88.4, 25.6, and 42.0, respectively. The average fortification recoveries of the MB, CV, LCV, MG, and LMG of the level of 0.8 mg/kg tested in fish muscle and feed samples were 99.68, 98.93, 100.49, 100.01, and 100.00%, respectively. The precision of analysis of analytes in fish muscle and feed ranged from 4% to 14% and from 7% to 14%, respectively. The decision limits (CCa) were 0.28e0.54 mg/kg, and the detection capabilities (CCb) were 0.35 e0.67 mg/kg (n ¼ 99). [ABSTRACT FROM AUTHOR]