Epitetracycline hydrochloride

A high-performance liquid chromatographic assay was developed to detect oxytetracycline (OTC) in chinook salmon muscle tissue. A solid-phase extraction protocol was used to recover OTC and the internal standard, epitetracycline hydrochloride, from the salmon tissue samples. OTC was analyzed using a mobile phase of methanol-0.02 M phosphate buffer, pH 2.25 (60:190), an ultraviolet detection wavelength of 365 nm and 250 mm x 4.6 mm I.D. Ultrasphere ODS column. A linear calibration curve (r2 = 0.999) of OTC in salmon muscle tissue from 0.05 to 3.0 ppm was obtained. Using a signal-to-noise ratio of 5:1, the OTC detection limit was 0.5 ppm in salmon muscle tissue. OTC recovery (74.4%) and intra-assay variability (2.3%) were optimized for salmon muscle tissue. An in vivo feeding study was performed by administrating OTC-medicated feed for a period of 10 days, followed by a 42-day sampling period. The half-life for the elimination of OTC in chinook salmon muscle tissue was found to be 5.4 days.

A captive striped skunk (Mephitis mephitis) study was conducted between February and June 2004 at the United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services National Wildlife Research Center, Fort Collins, Colorado, USA. The main objective was to determine the percentage of adult striped skunks that were marked after consuming placebo oral rabies vaccine (ORV) baits containing 100 mg of an experimental microencapsulated (coated microparticle) tetracycline hydrochloride biomarker. Biomarkers were identified in the canine teeth and mandibles of five of five skunks that consumed an ORV bait. A second objective was to determine if the microencapsulated tetracycline was resistant to photochemical conversion from tetracycline to epitetracycline. After 15 days of exposure, conversion from tetracycline to epitetracycline concentration in the microencapsulated product (mean 1.9% conversion, SD=1.24) was significantly less (P=0.006) than the pure-grade tetracycline powder (mean 7.5% conversion, SD=1.37). Results support the use of microencapsulated tetracycline hydrochloride as a biomarker in circumstances where the use of conventional powdered tetracycline hydrochloride is not feasible due to ORV bait design constraints.

In trying to estimate the separation efficiency of Capillary Electrophoresis (CE) methods, the resolution (RS), the number of theoretical plates (N) and the peak-to-valley ratio (p/v) are often used assessment criteria. This study demonstrates that these criteria are not as suitable to describe the separation efficiency in case of Capillary Zone Electrophoresis (CZE) methods as they are for Liquid Chromatography (LC) methods. The investigations were performed by means of a validated CZE method for the evaluation of tetracyclines and their related substances. Four impurities of tetracycline hydrochloride are described in the European Pharmacopoeia. Three were found in the sample used for our investigations, i.e. epi-tetracycline formed by keto-enol-tautomerism, anhydrotetracyclin and epi-anhydrotetracyline. It could be shown that higher values of these assessment criteria like RS do not necessarily represent better separation. Thus, a discussion on the usefulness of separation selectivity and efficiency as assessment criteria for capillary electrophoresis as well as on the introduction of additional parameters is needed.