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We present an official AACC reference method for the measurement of alkaline phosphatase, the culmination of optimization experiments conducted by a group of independent laboratories. The details of this method and evaluation of factors affecting the measurement are described. A metal ion buffer has been incorporated that maintains optimal and constant concentrations of zinc(II) and magnesium(II) ions. Final reaction conditions are: pH (30 degrees C), 10.40 +/- 0.05; 2-amino-2-methyl-1-propanol buffer, 0.35 mol/L; 4-nitrophenyl phosphate, 16.0 mmol/L; magnesium acetate, 2.0 mmol/L; zinc sulfate, 1.0 mmol/L; and N-(2-hydroxyethyl)ethylenediaminetriacetic acid, 2.0 mmol/L.

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Enzymatic substrate analysis is an attractive means of analysis in clinical chemistry because of its sensitivity and specificity. The GeMSAEC Fast Analyzer, in conjunction with a small computer, provides a means of performing routine enzymatic substrate analysis and offers the following advantages: (a) selectivity of approaches to enzymatic analysis, i.e., end-point or kinetic; (b) essentially parallel analyses of multiple samples, yielding a unique method for performing kinetic fixed-time analysis; (c) on-line data reduction, resulting in rapid calculation and output of results and the minimization of data handling errors; and (d) a small reagent volume per test (400 µl), which reduces the cost of analysis. The analysis of substrate with enzymatic end-point and kinetic procedures is examined by use of a computer-interfaced Fast Analyzer. Computer programs were written to facilitate this study. Glucose (hexokinase/GPD), urea (urease/GMD), and uric acid (uricase) have been used as examples in evaluating both end-point and kinetic analyses. The advantages and limitations of each type of analysis are presented, with the emphasis being placed on enzymatic substrate analysis and means by which the computer-interfaced Fast Analyzer can facilitate both end-point and kinetic analyses.

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