Oxytetracycline degradation in model meat processing systems

A RP-HPLC method was developed that successfully quantified mixtures of oxytetracycline (OTC), 4-epiOTC, á- and â-apoOTC down to 40, 20, 50 and 140 ng/ml at ambient temperature in less than 35 minutes. A 0.1M ammonium acetate buffer (pH 3.0)-acetonitrile-tetrahydrofuran (72.5:12.5:15, v/v/v) mobile phase was found by means of the statistical simplex method of solvent optimization to give excellent separation of compounds. Quantitative and reproducible isolation of OTC from aqueous and tissue matrices using solid-phase extraction (SPE) C18 cartridges was successful, whereas isolation of the degradation compounds, particularly á- and â-apoOTC from tissue, was not. Using this method, the degradation kinetics of OTC upon exposure to various meat processing parameters (heat, water activity, and the presence of certain additives) in aqueous and tissue matrices were studied. Regression analysis of ln-linear data revealed that pseudo-first order kinetics were observed for all matrices and parameters. Between 60 and 80°C, the rate of OTC degradation (kobs) increased several-fold. Glycerol-adjusted water activities (0.6 to 1.0) had only a minimal effect upon kobs (p > 0.05), although changes in the secondary kinetic parameters (enthalpy and entropy) were evident. Monomeric phosphate increased kobs in aqueous solution in accordance with a base-catalyzed reaction mechanism. Polymeric phosphates significantly decreased (p 0.05), although their secondary effects on the matrix altered the apparent stability of OTC. Binding studies provided evidence that OTC binding to tissue was due in part to complexing protein-bound cations. Experimental evidence indicated that mineral content was the primary factor affecting OTC degradation. Parameter manipulation did not appear to alter the rate-limiting mechanism (E2 elimination) by which OTC breakdown occurred, as was evidenced by the occurrence of enthalpy/entropy compensation. This research has provided a detailed database for the degradation of OTC. Enthalpy/entropy compensation was shown to be a potentially useful tool for studying OTC degradation

Aqueous biphasic systems: a benign route using cholinium-based ionic liquids

Ionic-liquid-based aqueous biphasic systems (ABS) have been the focus of a significant amount of research in the last decade. However, only (moderately) toxic and poorly biodegradable ionic liquids have been explored hitherto. Focusing on the development of more benign and sustainable approaches, a novel class of ABS using cholinium-based ionic liquids is proposed. For the first time, it is shown that a large assortment of cholinium-based ionic liquids is capable of undergoing liquid-liquid demixing in the presence of aqueous solutions with strong salting-out species. In order to assess the applicability of these systems for separation purposes, the partitioning of two antibiotics and/or their hydrochloride forms was also investigated. Cholinium-based ABS are shown to be improved routes for the extraction of pharmaceuticals, achieving complete extractions in a single-step by way of the proper tailoring of the phase forming components and their concentrations in the aqueous media

Current trends in sample preparation for growth promoter and veterinary drug residue analysis

This research was part-funded under the Food Institutional Research Measure (project reference number: 06RDTAFRC479) and Food for Health Research Initiative (project reference number: 07FHRITAFRC5), which was administered under the Irish Department of Agriculture, Fisheries and Food.peer-reviewedA comprehensive review is presented on the current trends in sample preparation for isolation of veterinary drugs and growth promotors from foods. The objective of the review is to firstly give an overview of the sample preparation techniques that are applied in field. The review will focus on new techniques and technologies, which improve efficiency and coverage of residues. The underlying theme to the paper is the developments that have been made in multi-residue methods and particularly multi-class methods for residues of licensed animal health products, which have been developed in the last couple of years. The role of multi-class methods is discussed and how they can be accommodated in future residue surveillance.Department of Agriculture, Food and the Marin