Analysis of tetracycline, oxytetracycline and chlortetracycline in plasma extracts by electrospray tandem mass-spectrometry and by liquid chromatography

Abstract Pure standards of tetracyclines (tetracycline, oxytetracycline and chlortetracycline) have been analyzed on a triple quadrupole mass spectrometer with Atmospheric Pressure Chemical Ionization (APCI) and Electrospray Ionization (ESI). ESI appeared to be considerably more sensitive than APCI. Collisional activation of the MH+ ions gave fragment ions at m/z values equal to MH+ - 35 which corresponds to loss of both H2O and NH3. The collisionally induced loss of 35 from MH+ was used in developing a mass spectrometric method based on loop injection and selected reaction monitoring (SRM) as the final analytical step. The method was tested on extracts from fortified plasma and the measurements from the MS-MS analysis were compared with results from High Performance Liquid Chromatography (HPLC) analysis of the same samples. The fortified plasma (from pig) samples were purified by chelate affinity chromatography (amberlite XAD columns). After filtration and evaporation of the solvent the redissolved resid...