Distribution and depletion of flubendazole and its metabolites in edible tissues of guinea fowl.

1. We measured the distribution and depletion of residues of flubendazole and its major metabolites in breast muscle, thigh muscle and liver of guinea fowls during and after oral administration of the veterinary medicine Flubenol 5% at two doses. 2. The guinea fowls were treated orally with normal feed, medicated at doses of 56 and 86 mg per kg feed for 7 successive days. Afterwards, depletion was observed for 8 d. Just before slaughter, body weights were measured. Thigh muscle, breast muscle and liver of three female and three male birds were sampled. The concentrations of the flubendazole-derived residues were determined by a liquid chromatographic-mass spectrometric method. 3. The highest residue concentrations were obtained for the reduced metabolite. With the therapeutic dose, the maximum mean residue concentrations obtained for this compound in thigh muscle, breast muscle and liver were 312, 288 and 1043 microg/kg, respectively. The values for flubendazole, the parent molecule, were 114, 108 and 108 microg/kg, respectively. The residues of the hydrolysed metabolite were negligible in the sampled muscle tissues. After 24 h of depletion, the sum of the residues of parent and metabolites in muscle tissue still exceeded 50 microg/kg. After 8 d of depletion, flubendazole-derived residues at low concentrations could still be measured in both muscle tissues and liver. Generally, the disposition of residues in breast and thigh muscle was comparable. 4. The European Union has not established a maximum residue limit (MRL) for flubendazole in edible tissues of guinea fowl. In contrast, the existing MRLs for other bird species are expressed as the sum of parent flubendazole and its hydrolysed metabolites. An estimated withdrawal period of three days will assure residue safety in the edible tissues of guinea fowl treated with flubendazole at therapeutic dose. After this withdrawal period following treatment of the guinea fowl, the residues were approximately constant, very low and far below the established safe MRL level for other bird species.

Determination of flubendazole and its metabolites in eggs and poultry muscle with liquid chromatography-tandem mass spectrometry.

The optimization of a quantitative and sensitive LC-MS/MS method to determine flubendazole and its hydrolyzed and reduced metabolites in eggs and poultry muscle is described. The benzimidazole components were extracted from the two matrices with ethyl acetate after the sample mixtures had been made alkaline. The HPLC separation was performed on an RP C-18 column with gradient elution, using ammonium acetate and acetonitrile as mobile phase. The analytes were detected after atmospheric pressure electrospray ionization on a tandem quadrupole mass spectrometer in MS/MS mode. The components were measured by the MS/MS transition of the molecular ion to the most abundant daughter ion. The overall extraction recovery values for flubendazole, the hydrolyzed metabolite, and the reduced metabolite in eggs (fortification levels of 200, 400, and 800 microg kg(-1)) and muscle (fortification levels of 25, 50, and 100 microg kg(-1)) were, respectively, 77, 78, and 80% and 92, 95, and 90%. The trueness (fortification levels of 400 and 50 microg kg(-1), respectively, for eggs and muscle), expressed as a percentage of the added values for these analytes, was, respectively, 89, 100, and 86 and 110, 110, and 98%. The proposed MS detection method operating in the MS/MS mode is very selective and very sensitive. The limits of detection for flubendazole and its hydrolyzed and reduced metabolites in egg and muscle were, respectively, 0.19, 0.29, and 1.14 microg kg(-1) and 0.14, 0.75, and 0.31 microg kg(-1). The limits of quantification were, respectively, 1, 1, and 2 microg kg(-1) and 1, 1, and 1 microg kg(-1). The discussed method was applied to a pharmacokinetic study with turkeys. Residue concentrations in breast and thigh muscle of turkeys orally treated with flubendazole were quantified. Medicated feed containing 19.9 and 29.6 mg kg(-1) flubendazole was provided to the turkeys for seven consecutive days. For the trial with the recommended dose of 19.9 mg kg(-1), one day after the end of the treatment, the mean sum of the flubendazole plus hydrolyzed metabolite residue values in thigh and breast muscle declined to below the maximum residue limit (50 microg kg(-1)) and were, respectively, 36.6 and 54.1 microg kg(-1). The corresponding values with the higher dose of 29.6 mg kg(-1) were, respectively, 101.7 and 119.7 microg kg(-1).

Development and validation of a liquid chromatography-electrospray tandem mass spectrometry method for mebendazole and its metabolites hydroxymebendazole and aminomebendazole in sheep liver.

A quantitative liquid chromatography-electrospray tandem mass spectrometry method for the determination of mebendazole and its hydrolysed and reduced metabolites in sheep liver has been developed and validated. The benzimidazole substances were extracted with ethyl acetate after the sample mixture had been made alkaline. The HPLC separation was performed on a reversed-phase C18 column with gradient elution using a mobile phase consisting of water containing 0.1% formic acid and acetonitrile. The analytes were detected after atmospheric pressure electrospray ionization on a tandem quadrupole mass spectrometer in MS-MS mode. The components were measured by the MS-MS transitions of the molecular ion to the two most abundant daughter ions. The detection limits are lower than 1 microg kg(-1). For this application, the validation limit was set at 50 microg kg(-1). The examined validation parameters were in accordance with the permitted tolerances ranges stipulated in the proposed new European validation criteria for residue surveillance. For the three analytes, the overall recovery was higher than 90%. The RSD for the repeatability ranged from 5 to 11%. The range for the within-laboratory reproducibility was between 2 and 17%. The decision limits for mebendazole, the hydrolysed and the reduced metabolite were 56.6, 61.8 and 64.2 microg kg(-1), respectively. The detection capabilities for these substances were 60.0, 86.1 and 90.9 microg kg(-1), respectively.

Confirmatory assay for the simultaneous detection of penicillins and cephalosporins in milk using liquid chromatography/tandem mass spectrometry.

A high-performance liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the detection of residues of penicillins and cephalosporins in milk has been developed. After a simple extraction with acetonitrile, the extract was directly injected into the LC/MS/MS system on a C(18) column. A gradient consisting of acetonitrile and water, each containing 0.1% formic acid, was applied. The abundant parent ions [M + H](+) produced by positive electrospray ionisation were selected for fragmentation with argon. For each compound at least one fragment was recorded with multiple reaction monitoring. The limits of detection ranged from 1.5 to 25 microg/kg and the limits of quantification ranged from 4 to 50 microg/kg. Recoveries were examined at three levels (MRL, 0.5 x MRL, 2 x MRL) and ranged from 57 to 88%. The coefficients of variation obtained for the repeatability experiments were in agreement with those specified by the Horwitz equation. Linearity was checked by injecting extracts of samples spiked with increasing amounts of the different standards ranging from 0 to 150 microg/kg. The advantage of this method over existing methods is the very simple sample pre-treatment which makes the method very suitable for routine analysis.

Validation of HPLC method of analysis of tetracycline residues in eggs and broiler meat and its application to a feeding trial.

HPLC with ion-pairing chromatography and diodearray detection at 355 nm was used to determine tetracycline antibiotics in eggs and broiler meat. The analytical methods were optimized and validated. The mean recovery values for oxytetracycline for eggs and for tetracycline for breast meat were 76%. The within-day precision ranged from 8.0 to 11.8% for oxytetracycline in eggs and from 6.1 to 15.5% for tetracycline in breast meat. The between-day precision was 4.8% and 5.0% respectively for oxytetracycline in eggs and tetracycline in breast meat. The limit of detection and the limit of quantitation for oxytetracycline in eggs were 2.2 and 13.0 ng/g respectively. These limits for tetracycline in breast meat were 10.5 and 20.9 ng/g respectively. Residue values of tetracycline antibiotics in eggs and broiler meat were determined after oral administration of medicated feed. Medicated feed with 840 mg/kg oxytetracycline was provided to laying hens for seven successive days. Two days after the administration was stopped, the mean oxytetracycline residue value in the eggs was already lower than the Maximum Residue Limit (MRL)-level and reached 118 ng/g. Broilers were supplied with medicated feed containing 480 mg/kg tetracycline for seven successive days. Four days after the administration was stopped, the mean tetracycline residue value in breast meat decreased below the MRL and was 86 ng/g.

Evaluation of a modified enzymatic test for the detection of tetracyclines in milk.

The tetracycline galactosidase (TG) test, a new method for the detection of tetracycline residues in raw milk based on the inhibition of beta-galactosidase biosynthesis in Escherichia coli, was previously validated with spiked milk samples. It has now been applied to milk from cows treated with oxytetracycline. In view of the occurrence of false positives, related to highly elevated somatic cell counts (>10(6)/ml), the improved TG test was developed, in which a heating step (80 degrees C, 15 min) preceded the original TG test protocol. A good agreement with other assays (Delvotest SP, the Bacillus cereus microtiter test, the LacTek tetracycline milk screening test, the Charm HVS-8100 tetracycline test) as well as with high-pressure liquid chromatography was obtained. No false negatives were observed with reference to the established maximum residue limit for tetracyclines of 100 microg/kg milk.