Monitoring antibiotic residues in honey

Authors; Monica Cristina Cara1, Gheorghita Simion1, Mirabela Panfiloiu2, Harieta Pîrlea3

Affiliation: 1 Directia Sanitar Veterinara si Pentru Siguranta Alimentelor Timis                                                                  2 S.C. Antarctica, Timisoara
                       3 Universitatea Politehnica Timisoara

Next to the β-lactam antibiotics in veterinary medicine, streptomycin is one of the mostly used antibiotics. High concentration of streptomycin could lead to ototoxic and nephrotoxic effects. Low concentration – as found in food – may cause allergies, destroy the intestinal flora and favor immunity to some pathogenic microorganisms. In 1948 chlortetracycline was isolated by Duggan as a metabolite and this was the first antibiotic substance of the group of tetracyclines. In the present paper there are presented the monitoring of the antibiotic residues in honey from Timis County. The residues of tetracycline and streptomycin in honey were determined by the method ELISA – a quantitative method of detection. The microtitre wells are coated with tetracycline and anti-streptomycin antibodies. Free antibiotic and immobilized antibiotic compete with the added antibiotic antibody (competitive immunoassay reaction). Any unbound antibody is then removed in a washing step. Bound conjugate enzymes convert the colorless chromogen into a blue product. The addition of the stop reagent leads to a color change from blue to yellow. The measurement is made photometrically at 450 nm. The absorption is inversely proportional to the antibiotic concentration in the sample.

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LC-MS/MS Analysis of albendazole and its metabolites in animal tissues

Authors: Ana Csuma, Ana Cismileanu                                                                                           Affiliation: S.N. Institutul Pasteur S.A., Bucuresti

Treating the animals with veterinary medicines raise the issue of residues that can persist in their edible tissues. In order to establish the withdrawal time necessary for depletion of the residues to sufficiently low concentration not to affect human health, biological tests performed on animals implicitly involve the use of sensitive and reliable analytical methods for residues determination. The aim of this work was to establish and validate a sensitive and reliable method for simultaneous determination of albendazole and its metabolites, albendazole sulfoxide, albendazole sulfone and 2-aminoalbendazole sulfone in animal tissues by LC/MS/MS. The method involves acid hydrolysis with 6N HCl in order to release most residues, in particular the bound metabolite 2-amino-albendazole sulfone especially from liver, followed by extraction with ethyl acetate and solid phase clean up of the extract on a C18 SPE cartridge. The liquid chromatographic separation was achieved on a XTerra MS C18 column (10 cm x 2,1 mm, 3,5 ìm), with gradient elution of 0,1% formic acid – methanol. Detection was performed by mass spectrometry in ESI+ mode. The limits of quantification were lower than 4 ìg/ml for each component.The correlation coefficients (R2) of the calibration curves (in the range from 0,01 ìg/ml to 0,5 ìg/ml) were higher then 0,9935. The relative standard deviations of repetability on samples naturaly contaminated from treated animals were between 5,75% and 11,6%. Recoveries from fortified muscles in the range of 10 ìg/kg to 100 ìg/kg were between 70,2% and 88% with relative standard deviation of 5,4% – 12,2%. For liver fortified in the range of 100 ìg/kg to 1000 ìg/kg recoveries between 70,3% and 83,2% were obtained with relative standard deviation of 5,7 %-11%.

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Contamination of food with residues of antibiotics in the sulphonamide class, a risk that can be avoided

Autori: Carmen Lidia Chițescu1, Anca Nicolau2

1 S.C. Pasteur, Filiala Filipesti,                                                                                                                     2 Universitatea Dunarea de Jos, Galati

Sulfadimethoxine, sulfamethoxazole, sulfaquinoxaline and sulfadiazine are the most common used sulfonamides in veterinary practice. The recommended withdrawal periods if not observed before slaughtering of the medicated animals, the products may obtain from such animals may be contaminated with residue. The interest in having reliable methods able to detect low amounts of sulfonamides in food is very actual. In this study, a multiresidue analysis was performed to simultaneously determine those four sulfonamides in chicken muscle tissue by the Waters LC. Criteria of validation: specificity, accuracy, precision, limit of detection, limit of quantification, and linearity, according to the European Commission Decision 2002/657/EC, show that the method can detect different kinds of sulfonamides within one run, without mass spectrometry analyses, or Fluor metric derivatization of analyts. The method is accurate, simple, economical in both time and cost, capable of detecting sulfonamides residues below the maximum residue limits (MRL) and easy to perform to routine samples, in normal condition of laboratory. The sulfonamides were extracted with acetonitrile and acetone and dichloromethane. N-hexane was added for defeating the sample. Separation was carried out on a Zorbax SB- C18 analytical column, using as mobile phase a mixture of 75:25 = di-natrium-hydrogenphosphat solution 6 g/1000 ml (pH = 8.5) : methanol. The detection wavelength was set at: 254 nm Calibration graphs were linear with very good correlation coefficients in the concentration range from 0.320 to 1.5ìg /mL. The limits of quantification (LOQ) for the sulfonamides were in the range of 6.6–0.34 ìg /kg. The recovery for spiked chicken muscle with 50–150 ìg/kg ranged more than 70%. The relative standard deviation (Reds) of the sulfonamides for six measurements at 50 go/kg, 100 ìg /kg and 150 ìg /kg was less then 15%. The applicability of the method to the analysis of chicken muscle tissue was demonstrated.

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