Flow injection determination of chlorpromazine by inhibition of glutamate dehydrogenase

A double injection flow procedure is used for the determination of chlorpromazine (less than or equal to 10 x 10(-5) M, in 44 mu l), by its inhibition of glutamate dehydrogenase (GlDH). The enzyme is injected into pH 7.5 phosphate buffer containing substrate (1 x 10(-3) M alpha-ketoglutaric acid) and 1 x 10(-3) M NH4Cl, and drug/NADH (8 x 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 x 10(-5) M drug (n=6) was 5.0%; the 3 sigma limit of detection was 2 x 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. (C) 1999 Elsevier Science B.V. All rights reserved.