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The assessment of a plasma melatonin assay using gas chromatography negative ion chemical ionization mass spectrometry.

It has been shown that negative ion chemical ionization can increase the sensitivity of the mass spectrometric assay of the pineal hormone melatonin. However, it is an exacting assay requiring extensive sample preparation which precludes its use as a general research tool. We have investigated different derivatizing reagents and reaction conditions to demonstrate that a simple negative ion chemical ionization assay can be developed which will measure low picogram or even femtogram levels of the hormone in samples where the data have been ambiguous.