Influence of Temperature on the Delta pH Method of Measuring Blood Cholinesterase.
Technical rept. Sep 73-Feb 74,
EDGEWOOD ARSENAL ABERDEEN PROVING GROUND MD
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Efforts to evaluate the precision of the Michel delta pH method of measuring cholinesterase activity, performed in a breaker immersed in a 25C water bath, resulted in unexpected variability in results of day-to-day replicate analyses. Most disturbing was the considerable variation between each 4-hour period of an 8-hour day a.m. and p.m. measurements. Precision of quadruplicate sets, expressed as coefficient of variation, ranged from plus or minus 0.5 to 8.0. By rigidly controlling temperature with a water-jacketed reaction vessel, the variation was reduced to plus or minus 1.7. A study of the effect of temperature on the method showed that a 1-degree change in temperature resulted in a 5.5 change in plasma activity and a 3.0 change in red cell activity. A graphing of the influence of temperature on reaction rate produced a linear relationship. Identical thermodynamic data were obtained with plasma and red cell samples which were inhibited 50 with an with an irreversible anticholinesterase agent. Author