A noncompetitive flow injection immunoassay method has been developed to assay small haptens. In this assay the sample containing the hapten is incubated with excess enzyme-labeled monovalent antibody for a brief period. The excess antibody is then separated from the bound antibody by eluting through an antigen-immobilized immunoaffinity column. The enzyme label of the eluting antibody-hapten complex is fluorometrically detected. The applicability of the method is demonstrated by assaying alpha-(difluoromethyl)ornithine (DFMO), an anticancer drug in human plasma samples. The assay is sensitive enough to detect 200 amol of DFMO. Interferences from other similar endogenous amines have been eliminated by selective immunoaffinity purification of the antibodies.

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Three interlaboratory round-robin studies (RR1, RR2, and RR3) were conducted to identify a serum-based reference material that would aid in the standardization of direct ion-selective electrode (ISE) measurements of sodium and potassium. Ultrafiltered frozen serum reference materials requiring no reconstitution reduced between-laboratory variability (the largest source of imprecision) more than did other reference materials. ISE values for RR3 were normalized by the use of two points at the extremes of the clinical range for sodium (i.e., 120 and 160 mmol/L), with values assigned by the flame atomic emission spectrometry (FAES) Reference Method. This FAES normalization of ISE raw values remarkably improved all sources of variability and unified the results from seven different direct ISE analyzers to the FAES Reference Method value. Subsequently, a three-tiered, fresh-frozen human serum reference material was produced to the specifications developed in RR1-RR3, was assigned certified values for sodium and potassium by Definitive Methods at the National Institute of Standards and Technology (NIST), and was made available in 1990 to the clinical laboratory community as a Standard Reference Material (SRM); it is now identified as SRM 956. Albeit retrospectively, we show how applying an FAES normalization step identical to that used in RR4/5 to the ISE data for SRM 956 after the NIST Definitive Method values were known, consistently moved the ISE results for RR3 closer to the true value for Na+ and K+.

This review discusses the analytical applications of monoclonal antibodies specific for enzymes. One important, but not well-studied, application of these monoclonal antibodies is their use in immobilizing enzymes on solid supports. This method is based on binding the enzymes to an immobilized antibody through the antigen binding site of the antibody. Enzymes immobilized this way retain much of their activity. The utility of immobilized enzyme reactors prepared by immobilizing the enzymes through antibodies is demonstrated by using them in the determination of acetylcholine and choline in brain tissue extracts. Currently available methods for immobilizing antibodies and enzymes are reviewed. Other issues discussed in this review include the problems and advantages of immobilized enzyme reactors, especially when used in conjunction with HPLC. In addition, the applications of monoclonal antibodies for the detection and measurement of enzymes and their isoforms are summarized.

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