The effect of cooking on veterinary drug residues in food: nicarbazin (dinitrocarbanilide component).

The change of concentration of residues of the marker compound for the anti-coccidial drug nicarbazin, N,N'-bis(4-nitrophenyl)urea (dinitrocarbanilide, DNC), was investigated in model oil and aqueous solutions and in chicken muscle and egg. In model aqueous solutions, DNC decreased rapidly in concentration upon heating followed by a much more gradual decomposition. The curves produced when this information was plotted were not typical of exponential decay.

Effect of cooking on veterinary drug residues in food. Part 9. Nitroimidazoles.

Most food containing drug residues is consumed after cooking or processing, yet surveillance for these residues is almost always conducted on raw tissue. This investigation was to establish the effect of cooking on residues of the nitroimidazole drugs dimetridazole and ronidazole in chicken muscle and egg, to enable dietary intake calculations based on surveillance results. In model aqueous and lipid solutions, dimetridazole and its 2-hydroxy metabolite, which is usually found when residues are present, were relatively stable for times and temperatures normally encountered during standard cooking methods.

Extension of multi-residue methodology to include the determination of quinolones in food.

The multi-residue procedure for basic drugs described elsewhere by this laboratory has been evaluated for quinolone and fluoroquinolone antibiotics. The fluoroquinolones are a relatively new class of drug and an increasing number of licensed products containing these compounds are becoming available for use in animal husbandry. This, along with the possibility of the development of antibiotic resistant human pathogens, make it an important class of drug for which methodology is required for the monitoring of residues in food.

Screening and confirmation of triphenylmethane dyes and their leuco metabolites in trout muscle using HPLC-vis and ESP-LC-MS.

An extraction and clean-up protocol for the determination of Malachite Green and Crystal Violet and the corresponding leuco compounds in trout muscle has been developed. Final determination is by HPLC with visible (screening) or ESP-MS (confirmation) detection. In both cases lead(IV) oxide was used on-line to oxidise the leuco compounds back to the parent after chromatographic separation and prior to detection.

The effect of cooking on veterinary drug residues in food. Part 8. Benzylpenicillin.

The stability of benzylpenicillin to heat and cooking was studied. Stability of this compound in water (at 100 degrees C and 65 degrees C), 5% ethanol, 5% sodium bicarbonate, pH 5.5 buffer at 100 degrees C and in hot cooking oil at 140 degrees C and 180 degrees C was established.

The effect of cooking on veterinary drug residues in food: 4. Oxytetracycline.

The heat stability of oxytetracycline (OTC) in water and vegetable oil was investigated. Results showed that the drug was unstable in water at 100 degrees C with a half-life of about 2 min, but more stable in oil at 180 degrees C where the half-life was about 8 min. The effect of a range of cooking processes including microwaving, boiling, roasting, grilling, braising and frying on OTC residues in incurred animal tissues was investigated.

Determination of quinoxaline carboxylic acid (metabolite of carbadox) in animal tissue by HPLC.

A method for the determination of residues of quinoxaline-2-carboxylic acid (QCA), the major metabolite of carbadox, in pig kidney has been developed. Tissue samples were subjected to alkaline hydrolysis, liquid-liquid extractions, ion-exchange chromatography and further extraction to concentrate the analyte and purify the extract. Determination was by reverse phase HPLC with UV detection at 320 nm.

Analysis of trace residues of tetracyclines in animal tissues and fluids using metal chelate affinity chromatography/HPLC.

A novel method of analysis for the trace residue determination of tetracyclines in animal tissues and fluids has been developed. Clean-up of sample extracts is based upon the specific ability of tetracyclines to chelate with divalent metal ions (metal chelate affinity chromatography, MCAC) and determination made by high-performance liquid chromatography. The method has been tested for the determination of oxytetracycline (OTC), tetracycline (TC) and chlortetracycline (CTC) in porcine kidney and muscle, ovine kidney, bovine kidney and milk, and trout muscle.