Determination of phosphate and phosphite in plant material by gas chromatography-mass spectrometry and ion chromatography

Abstract

A method is described for the rapid and simultaneous detection of phosphate and phosphite in samples of plant material as small as 10 mg fresh weight. Samples are extracted into formic acid-isopropanol, clarified by the addition of chloroform and partially purified by sequential passage through cation- and anion-exchange resins. The analytes can then be separated directly by single-column anion-exchange chromatography using a conductivity detector. Alternatively they can be separated by capillary gas chroamtography after the formation of tert.-butyldimethylsilyl esters. Recoveries of 95% or better were achieved, estimated both by the addition of 32P or by mass addition. The lower limit of detection was 100 ng using ion chromatography and 100 pg with mass spectrometry.