Interference by S-nitroso compounds with the measurement of nitrate in methods requiring reduction of nitrate to nitrite by cadmium

Various methods suited for the measurement of nitrate require its reduction to nitrite by cadmium under acidic or alkaline conditions. N-G-Nitroargini ne analogs have been shown to interfere with the measurement of nitrate by such assays. In the present work we show by gas chromatography-mass spectro metry that under alkaline reduction conditions the S-nitroso compounds S-ni trosoglutathione and S-nitrosohomocysteine but not S-nitroso-N-acetylcystei ne and S-nitroso-N-acetylpenicillamine can considerably contribute to nitra te and thus interfere with its measurement. Our results suggest that S-nitr oso compounds may interfere with the measurement of nitrate in methods requ iring cadmium-catalyzed reduction of nitrate to nitrite. (C) 1999 Elsevier Science B.V. All rights reserved.