Simple and rugged SPE method for the determination of tetracycline antibiotics in serum by HPLC using a volatile mobile phase

A simple and rugged SPE method for the determination of tetracycline (TC), minocycline (MC) and demeclocycline (DCC) in pot-cine serum by high performance liquid chromatography (HPLC) was developed. The spiked serum sample was pretreated with 2% phosphoric acid followed by a simple and rugged solid-phase extraction procedure using the Oasis(TM) HLB extraction cartridges. High and reproducible recoveries were obtained even though the cartridges were run dry. The extracted sample analytes were injected onto a Waters Symmetry Shield(TM) RPs column. The mobile phase was a simple volatile solution containing 0.1% TFA, 2% methanol and 7% acetonitrile in Water. The antibiotics were detected at 350 nm. The calibration curves were linear from 2.0 to 25.0 mu g mL(-1) of TC and MC with DCC as the internal standard at a concentration of 25.0 mu g mL(-1). For six replicate analyses, the average recoveries of TC and MC from porcine serum sample fortified at the level of 2.5 mu g mL(-1) were 96.1% with 1.3% RSD and 101% with 0.54% RSD; at level of 0.5 mu g mL(-1) the average recoveries were 88% with 1.6% RSD and 97.8% with 1.4% RSD.