Sixteen laboratories participated in a collaborative study to evaluate method performance parameters of a liquid chromatographic method of analysis for paralytic shellfsh toxins (PST) in blue mussels (Mytilus edulis), soft shell clams (Mya arenaria), sea scallops (Placopectin magellanicus), and American oysters (Crassostrea virginicus). The specifc analogs tested included saxitoxin, neosaxitoxin, gonyautoxins-1 to -5, decarbamoyl-gonyautoxins-2 and -3, decarbamoyl-saxitoxin, and N-sulfocarbamoylgonyautoxin-2 and -3. This instrumental technique has been developed as a replacement for the current AOAC biological method (AOAC Offcial MethodSM 959.08) and an alternative to the pre-column oxidation LC method (AOAC Offcial MethodSM 2005.06). The method is based on reversed-phase liquid chromatography with post-column oxidation and fluorescence detection (excitation 330 nm and emission 390 nm). The shellfsh samples used in the study were prepared from the edible tissues of clams, mussels, oysters, and scallops to contain concentrations of PST representative of low, medium, and high toxicities and with varying profles of individual toxins. These concentrations are approximately equivalent to ½ maximum level (ML), ML, or 2×ML established by regulatory authorities (0.40, 0.80, and 1.60 mg STX·diHCl eq/kg, respectively). Recovery for the individual toxins ranged from 104 to 127%, and recovery of total toxin averaged 116%. Horwitz Ratio (HorRat) values for individual toxins in the materials included in the study were generally within the desired range of 0.3 to 2.0. For the estimation of total toxicity in the test materials, the reproducibility relative standard deviation ranged from 4.6 to 20%. A bridging study comparing the results from the study participants using the post-column oxidation (PCOX) method with the results obtained in the study director’s laboratory on the same test materials using the accepted reference method, the mouse bioassay (MBA; AOAC Offcial MethodSM 959.08), showed that the average ratio of results obtained from the two methods was 1.0. A good match of values was also achieved with a new certifed reference material. The results from this study demonstrated that the PCOX method is a suitable method of analysis for PST in shellfsh tissue and provides both an estimate of total toxicity, equivalent to that determined using the MBA AOAC Offcial MethodSM 959.08, and a detailed profle of the individual toxin present in the sample.

Quantitative methods using liquid chromatography coupled with tandem mass spectrometry were developed for seven kinds of aminoglycoside antibiotics in kidney and muscle tissues. Mass spectral acquisition was performed in the positive-ion mode by applying multiple reaction monitoring. Liquid chromatographic separation employed a ZIC-HILIC column (SeQuant) for hydrophilic interaction chromatography. Extraction of the aminoglycosides was performed using liquid extraction with a phosphate buffer containing trichloroacetic acid, followed by a solid-phase clean-up procedure on a weak cation-exchange column with carboxypropyl (CBX) SPE cartridge (Mallinckrodt Baker). The limits of quantification were 25 ng g(-1) for gentamicin, 50 ng g(-1) for spectinomycin, dihydrostreptomycin, kanamycin and apramycin, and 100 ng g(-1) for streptomycin and neomycin. These are well below the maximum residue limits set by the Codex Alimentarius Commission. The recoveries of all compounds from all tissues fortified at the level of quantification limits of 500 and 1000 ng g(-1) were >70%, and the variability (relative standard deviation) was generally <12%.

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Procaine penicillin G was administered by intramuscular (i.m.) injection to groups of healthy 100 kg market pigs at the approved label dose (15,000 IU/kg body weight), once daily for three consecutive days; or an extra-label dose (66,000 IU/kg body weight), once daily for five consecutive days. Penicillin G residue depletion was followed in plasma, tissue and injection sites using a liquid chromatographic method. Groups of pigs were killed 1, 2, 3, 4, 5 and 8 days after the last injection with the label dose. Penicillin G was not detected in liver after 1 day of withdrawal, in muscle and fat after 2 days of withdrawal, in plasma after 4 days of withdrawal, in skin after 5 days of withdrawal, or in kidney and the injection sites after 8 days of withdrawal. Other groups of pigs were killed 1, 2, 3, 5 and 7 days after injection with the extra-label dose. In these pigs penicillin G was not found in liver after 2 days of withdrawal, in fat after 3 days of withdrawal, or in the muscle, skin, plasma and injection sites after 7 days of withdrawal. Penicillin G was found at all times in the kidneys of the groups of pigs that received the high dose. The technique used for neck injections was critical to obtain intramuscular rather than intermuscular injections. The Bureau of Veterinary Drugs, Health Protection Branch, Health Canada calculated that the appropriate withdrawal period for pigs was 8 days for a dose of 15,000 IU procaine penicillin G/kg body weight and 15 days for a dose of 66,000 IU/kg.

1988. Effect ofthe feed additives chlofietracycline, monensin and lasalocid on feedlot performance of finishing cattle, liver lesions and tissue levels of chlortetracycline.Can. J. Anim. Sci (CON). L'ingestion de matidre sdche des sujets ayant requ de la CTC est 6galement plus 6lev6e que celle des animaux nourris de la ration CON. La CTC n'influe pas sur I'indice de consommation, mais la compl6mentation ir la MON ou ir la LAS 1'am6liore par rapport aux sujets nourris de la ration CON. Au cours de la p6riode d'alimentation riche en concentrds, I'inclusion d'additifs alimentaires n'am6liore pas significativement le gain moyen quotitidien ni I'ingestion de matidre sbche comparativement aux sujets nourris de la ration Can.