A simple and rapid LC-MS/MS method for the determination of amphenicols in Nile tilapia.

A quantitative method for analysis of amphenicols (chloramphenicol - CAP, thiamphenicol - TAP and florfenicol - FF) in Nile tilapia using LC-MS/MS is described. A simple sample preparation procedure was optimized using a Plackett-Burman design. The method was validated in accordance with Decision 2002/657/EC. Repeatability and reproducibility were less than 10.7% and 16%, respectively, for all compounds. Recoveries varied from 79.8% to 92.0%. CCα was 0.019, 54.81 and 54.93 µg.kg-1 for CAP, FF and TAP, respectively. CCß was 0.068, 64.88 and 58.91 µg.kg-1 for CAP, FF and TAP, respectively. Limits of quantification (LOQ) were 12.5 µg.kg-1 for FF and TAP and 0.15 µg.kg-1 for CAP. Nile tilapia fillets (n = 32) analyzed did not contain chloramphenicol. Thiamphenicol was detected in one sample (3.1%) and florfenicol was detected in every sample, all of them at concentrations below the maximum residue limit.

Quinolones and tetracyclines in aquaculture fish by a simple and rapid LC-MS/MS method.

The determination of antimicrobials in aquaculture fish is important to ensure food safety. Therefore, simple and fast multiresidue methods are needed. A liquid chromatography tandem mass spectrometry method was developed and validated for the quantification of 14 antimicrobials (quinolones and tetracyclines) in fish. Antimicrobials were extracted with trichloroacetic acid and chromatographic separation was achieved with a C18 column and gradient elution (water and acetonitrile). The method was validated (Decision 2002/657/EC) and it was fit for the purpose. Linearities were established in the matrix and the coefficients of determination were ≥0.98. The method was applied to Nile tilapia and rainbow trout (n = 29) and 14% of them contained enrofloxacin at levels above the limit of quantification (12.53-19.01 µg.kg-1) but below the maximum residue limit (100 µg.kg-1). Even though prohibited in Brazil and other countries, this antimicrobial reached fish. Measures are needed to ascertain the source of this compound to warrant human safety.

A simple, fast and sensitive screening LC-ESI-MS/MS method for antibiotics in fish.

The objective of this study was to develop and validate a fast, sensitive and simple liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method for the screening of six classes of antibiotics (aminoglycosides, beta-lactams, macrolides, quinolones, sulfonamides and tetracyclines) in fish. Samples were extracted with trichloroacetic acid. LC separation was achieved on a Zorbax Eclipse XDB C18 column and gradient elution using 0.1% heptafluorobutyric acid in water and acetonitrile as mobile phase. Analysis was carried out in multiple reaction monitoring mode via electrospray interface operated in the positive ionization mode, with sulfaphenazole as internal standard. The method was suitable for routine screening purposes of 40 antibiotics, according to EC Guidelines for the Validation of Screening Methods for Residues of Veterinary Medicines, taking into consideration threshold value, cut-off factor, detection capability, limit of detection, sensitivity and specificity. Real fish samples (n=193) from aquaculture were analyzed and 15% were positive for enrofloxacin (quinolone), one of them at a higher concentration than the level of interest (50µgkg-1), suggesting possible contamination or illegal use of that antibiotic.

Bioactive amines in soy sauce: validation of method, occurrence and potential health effects.

The objective of this study was to investigate the levels of bioactive amines in soy sauce. A method for the extraction of amines was optimized and an ion pair-HPLC method was validated. Overall, tyramine was the prevalent amine, followed by putrescine, histamine, phenylethylamine and cadaverine. The concentrations of amines varied widely among samples. The brands could be divided into two groups. The first one contained three amines; there was prevalence of cadaverine followed by tyramine and putrescine; and total amine levels were low. The second group contained four amines; there was prevalence of tyramine followed by histamine, phenylethylamine and putrescine; and total amine levels were high. A brand with lower NaCl levels contained significantly higher amine levels. Based on the levels of amines detected, a high percentage of samples could cause adverse effects to human health.