GAS-CHROMATOGRAPHIC DETERMINATION OF SODIUM MONOFLUOROACETATE AS THE FREE ACID IN AN AQUEOUS SOLVENT

A procedure was developed for the determination of sodium monofluoroacetate as the free acid by capillary gas chromatography with mass-selective detection. Commercially available polyethylene glycol capillary columns were compatible with injections of highly acidic aqueous solutions which were required for this relatively strong acid. Using monochloroacetic acid as an internal standard, a coefficient of variation of less than 2% was routinely obtained from replicate injections of a 100 mug/ml solution of sodium monofluoroacetate in 1 M HCl. The monofluoroacetic acid/monochloroacetic acid detector response ratio was a linear function of sodium monofluoroacetate concentration from 5 to 200 mug/ml. Since derivatization is not required and mass spectrometric identification of monofluoroacetic acid is obtained, the method offers advantages over previously described chromatographic methods for the determination of sodium monofluoroacetate. The average analyte recovery from 30 to 40 g biological samples fortified with between 2.5 and 100 mg of sodium monofluoroacetate was 81% with relative standard deviation typically less than 7%. The instrument limit of detection was 200 pg sodium monofluoroacetate when the detector was operated in the selected ion monitoring mode.