Flow injection analysis of trace amounts of NADH with inhibited chemiluminescent detection

The flow injection analysis of NADH was developed based on its inhibitory effect on a luminol–potassium hexacyanoferrate(III) chemiluminescence (CL) system. Under the optimum conditions, the decreased CL intensity was linear to the NADH concentration in the range of 5.0×10−8–2.0×10−5 mol l−1. The relative standard deviation was 1.24% for eight determinations of 1.0×10−6 mol l−1 NADH and the detection limit (3sb1/S) was 2.0×10−8 mol l−1. The study of interfering substances was also performed and the method was applied to the direct determination of trace amounts of NADH in synthetic samples with satisfactory results. Moreover, the inhibitory mechanism of CL was investigated with CL spectra, fluorescence spectra and UV–visible absorption spectra.