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)-Nitroarginine analogs have been shown to interfere with the measurement of nitrate by such assays. In the present work we show by gas chromatography-mass spectrometry that under alkaline reduction conditions the S-nitroso compounds S-nitrosoglutathione and S-nitrosohomocysteine but not S-nitroso-N-acetylcysteine and S-nitroso-N-acetylpenicillamine can considerably contribute to nitrate and thus interfere with its measurement. Our results suggest that S-nitroso compounds may interfere with the measurement of nitrate in methods requiring cadmium-catalyzed reduction of nitrate to nitrite.