Haemoglobin Interference in the Bichromatic Spectrophotometry of NAD(P)H at 340/380 nm

The negative bias observed in the NADPH-based bichromatic measurement of glucose in haemolysates (da Fonseca-Wollheim, F., Heinze, K.-G. & Liss, E. (1992) Temperature-dependent matrix effect in the direct enzymatic measurement of blood glucose, this journal 30, 371—375) is caused by shifts in the UV absorbance of haemoglobin which affect the absorbance difference ΔΑ340/38θηιη· la model experiments with haemoglobin solutions, spectral changes resulting in decreases of the absorbance at 340 nm and/or increases at 380 nm were found to occur for the following three reasons: