“…This is due to the fact that the inherent selectivity of enzymes is such that direct determination of a single species in a complex mixture is often possible without prior separation. In principle, enzymatic methods are sufficiently specific so that inherently nonspecific detection systems including pH-stats (4, 5), conductometers (6, 7) and enthalpimeters (8,9) may be used to measure sample concentration. Many analytical chemists have been reluctant to use enzymes because of their expense and instability, as well as the difficulties experienced in attaining adequate precision in kinetic assays.…”