Analysis of ascorbate and dehydroascorbate in plant extracts by high-resolution selected ion monitoring gas chromatography mass spectrometry

Here we report on the quantitative analysis of tert.-butyldimethylsilyl derivatives, of ascorbate and dehydroascorbate in plant extracts by high-resolution selected ion monitoring gas chromatography-mass spectrometry. The analysis involved an isotope dilution assay using [C-13(1)]ascorbate and [C-13(1)]dehydroascorbate. The limit of detection was approximately 0.5 pg for ascorbate and 5 pg for dehydroascorbate. The reproducibility of the whole quantification procedure, from extraction of Pinus sylvestris needles with 5% trichloroacetic acid to the final analysis, was very high: giving a relative standard deviation (R.S.D.) of 4% and 10% for ascorbate and dehydroascorbate, respectively. The reproducibility of the analysis of the redox ratio of ascorbate/(ascorbate+dehydroascorbate) was even higher (R.S.D.=1%). The high-resolution selected ion monitoring gas chromatography-mass spectrometry methodology developed here with very high sensitivity and specificity for ascorbate and dehydroascorbate opens new perspectives for investigations on distribution patterns of these substances in plants. (C) 1997 Elsevier Science B.V.