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Sodium salicylate was administered to rabbits in order to compare its disposition with that in other major and minor agricultural species. A dose of 44 mg/kg was given orally (p.o.) or intravenously (i.v.), and plasma and urine samples were collected for 36 h and 96 h, respectively. The majority of the drug was excreted as salicylic acid (SA) within 12 h. The major metabolites following an oral dose were salicyluric acid (SUA) and the glucuronide conjugates of SA and SUA. Following i.v. dosing, sulfate conjugates of both SA and SUA were also evident. Both SA and SUA were detected in plasma. Following i.v. administration, SA was distributed with a Vss of 0.249 +/- 0.082 l/kg and cleared at a rate of 0.0432 +/- 0.006 l/h/kg. The biological half-life, calculated from the terminal disposition-rate constant, was 4.3 h (i.v.) or 9.7 h (p.o.). The urinary elimination pattern of SA and metabolites in the rabbit was similar to that previously reported by our laboratories for cattle and goats, although total recovery of the administered dose was not as high as for the latter two species. However, the volume of distribution was larger than for cattle and goats, and rabbits cleared the drug more slowly than those species. As a consequence, the biological half-life was eight to ten times longer than in the ruminants studied previously.

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A multlresldue method for the isolation and liquid chromatographic determination of oxytetracycline (OTC), tetracycline (TC), and chlortetracycllne (CTC) antibiotics In milk Is presented. Blank and tetracycline (OTC, TC, and CTC) fortified milk samples (0.5 mL) were blended with octadecylsllyl (C18, 40 /an, 18% load, endcapped, 2 g) derivatized silica packing material containing 0.05 g each of oxalic acid and dlsodlum ethylenedlamlnetetraacetlc. A column made from the C18/milk matrix was first washed with hexane (8 mL), following which the tetracyclines were eluted with ethyl acetate-acetonltrlle (1 + 3; v/v). The eluate contained tetracycline analytes that were free from Interfering compounds when analyzed by liquid chromatography with UV detection (photodiode array, 365 nm). Correlation coefficients of standards curves for Individual tetracycline isolated from fortified samples were linear (from 0.982 ± 0.009 to 0.996 ± 0.004) with average percentage recoveries from 63.5 to 93.3 for the concentration range (100,200,400,800,1600, and 3200 ng/ mL) examined. The Inter-assay variability ranged from 8.5 ± 2.4% to 20.7 ± 13.0% with an Intra-assay variability of 1.0- 9.3%.

Journal of Liquid ChromatographyPublication details, including instructions for authors and subscription information: ABSTRACT A m u l t i r e s i d u e method f o r t h e i s o l a t i o n and h i g h performance 1 i q u i d chromatographic (photodiode array, UV 270nm) determination o f s u l f a t h i azole, s u l f i soxazole, sul f amerazine, sul f amethazine, s u l famethoxazole, sul fi soxazol e and sulfadimethoxine i n a m i 1 kbased i n f a n t formula i s presented. Blank o r sulfonamide spiked i n f a n t formula samples were blended w i t h o c t a d e c y l s i l y l d e r i v at i z e d s i l i c a (C-18) packing m a t e r i a l . A column made from t h e C -l 8 / i n f a n t formula m a t r i x was f i r s t washed w i t h hexane f o l l o w i n g which the sulfonamides were e l u t e d w i t h methylene c h l o r i d e . The e l u a t e contained sulfonamide analates which were f r e e from i n t e rf e r i n g compounds when analyzed by l i q u i d chromatography. T h i s r e s u l t e d i n c o r r e l a t i o n c o e f f i c i e n t s (0.9973 t 0.0016 t o 0.9992 t 0.0006), recovery percentages (75.91 t 1 1 . 1 2 r t o 112.01 t 8 . 1 5 q and i n t e r -(5.51 2 1.74% t o 15.27 K14X) and i n t r a -a s s a y (1.71 1601 1602 LONG ET AL. to 8.89%) variabilities for individual sulfonamides, over the concentration range (62.5 to 2000 ng/mL) examined, that are indicative of a useful method for the rnultiresidue analysis of milk-based infant formula for the presence of sulfonamides.