Flow injection determination of chlorpromazine by inhibition of glutamate dehydrogenase Original Research Article

A double injection flow procedure is used for the determination of chlorpromazine (≤10×10−5 M, in 44 μl), by its inhibition of glutamate dehydrogenase (GlDH). The enzyme is injected into pH 7.5 phosphate buffer containing substrate (1×10−3 M α-ketoglutaric acid) and 1×10−3 M NH4Cl, and drug/NADH (8×10−5 M) solution is injected from a second valve in series into the enzyme zone. The relative standard deviation for the determination of 6×10−5 M drug (n=6) was 5.0%; the 3σ limit of detection was 2×10−5 M. Although GlDH was successfully immobilised on controlled pore glass, and showed good activity between pH 7.0 and 8.5 in a single channel manifold, it was not inhibited by chlorpromazine. Possible reasons for this behaviour are given.