Residual fluorescence as an index of purity of reduced nicotinamide adenine dinucleotide.

Determination of fluorescence remaining after reduced nicotinamide adenine dinucleotide (NADH) has reacted with excess acetaldehyde in the presence of alcohol dehydrogenase (EC 1.1.1.1) is useful as a criterion of NADH purity when used in conjunction with other methods for determining purity such as the rate of reaction, the ratio of ultraviolet absorbances at 260 nm and 340 nm, the color, and the chromatographic homogeneity of the preparation. Measurement of residual fluorescence monitors the enzymatically inactive material which absorbs at 340 nm. The specific optical rotations of NADH at several wavelengths are also reported.