Clean and rapid liquid chromatographic technique for monitoring of oxytetracycline and sulphadimicline in milk without use of organic solvents

A clean method without use of organic solvents has been developed for isolation and high-performance liquid chromatographic (HPLC) determination of oxytetracycline (OTC) and sulphadimidine (SDD) in cows milk Isolation is rapid and simple - homogenization with an inorganic acid solution by means of a handy ultrasonic homogenizer, which is easy-to-use and portable, followed by centrifugation. Reversed-phase HPLC was performed on a C-4 column, with 1.25 mmol L-1 succinic acid solution as mobile phase, and identification was by means of a photodiode-array detector. Separation of the analytes was achieved in less than 8 min. Significant linearity was established over the concentration range of 0.1 - 1.0 mug mL(-1) for both target compounds (r > 0.99, P < 0.01). Average recoveries of OTC and SDD (each spiked at 0.1 - 1.0 mug mL(-1)) were greater than or equal to 88.8, and inter- and intra-assay variability was less than or equal to 2.8%. The total time required for analysis of one sample was < 20 min. The limits of quantitation of the method (mu g mL(-1) in milk) were 0.044 for OTC and 0.023 for SDD. No organic solvent was used at any stage of the analysis.