Ultratrace determination of highly hydrophilic compounds by 2,2,3,3,4,4,5,5-octafluoropentyl chloroformate-mediated derivatization directly in water

Highly hydrophilic compounds, with multiple carboxylic, hydroxylic, or amin ic groups, have been determined at ultratrace level (3-30 fmol injected) in aqueous solution by direct derivatization with 2,2,3,3,4,4,5,5-octafluorop entyl chloroformate, followed by n-hexane extraction and analysis by gas ch romatography-electron capture negative ion mass spectrometry (GC-ECNI-MS). The products have high molecular weights, but also high volatility, making their elution from the GC column efficient. The derivatizing agent was synt hesized from the corresponding alcohol and phosgene. The derivatization rea ction is catalyzed by a pyridine solution of N,N-dicyclohexylcarbodiimide. At 200 degrees C ion-source temperature, most negative ion mass spectra sho wed only a weak or no molecular ion, but a controlled and interpretable fra gmentation, allowing the derivatives to be easily monitored by high-mass io n chromatograms. Typical distinctive fragments are located in the m/z 500-8 00 mass range. Optimization of the operating conditions for the derivatizat ion was performed. This was done in order to minimize number and intensity of peaks due to the hydrolysis of chloroformate in the total ion chromatogr am. Calibration curves proved linear over two orders of magnitude concentra tion. (C) 1999 American Society for Mass Spectrometry.