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.

Design features and operation of a prototype miniaturized Fast Analyzer are described, and some results obtained with it are presented. The Analyzer occupies only one cubic foot of space. It has a 17-cuvet plastic rotor that rotates through a stationary optical system at speeds up to 5000 rpm. The resulting centrifugal force is utilized to transfer and mix a series of sample(s) and reagent(s) into the cuvets. The ensuing reactions are monitored spectrophotometrically, and the data evaluated in real time by an on-line computer. Samples (1 to 10 µl) and reagents (70 to 110 µl) are loaded into the rotor either discretely or dynamically; various rotor configurations can be used to do this. Many of the standard clinical analyses, including most of the NADH-linked enzymatic analyses, have been adapted for use with this analyzer. Precision obtained ranges from 1 to 4%. This report considers, specifically, analyses of some serum enzymes. Results show that the small analyzer possesses the previously demonstrated advantages of Fast Analyzers and, in addition, has several beneficial features arising from miniaturization.

A modified version of a previously described miniature Fast Analyzer [Clin. Chem. 18, 753 (1972)] was used as the basis for developing a compact, potentially portable, analytical system. This system includes an automated and versatile sample-reagent loader, a miniature Fast Analyzer, several plastic rotors and their cleaning station, and a portable data system. The sample-reagent loader combines a unique turntable assembly and two "Micromedic" pipets to quickly (5 min per rotor), accurately, and precisely obtain, transfer, and dispense small volumes of sample (1 to 10 µl of sample, 50 µl of diluent) and reagent (20 µl of reagent, 50 µl of diluent) into their respective cavities in a 17-cuvet rotor. The loader uses separate sample and reagent carousels, which allows operation of the system in either the single-sample—multiple-chemistry, multiple-sample— single-chemistry, or multiple-sample—multiple-chemistry analytical modes. The miniature Fast Analyzer rotates a loaded 17-cuvet rotor through a stationary optical system at speeds up to 5000 rpm. The resulting centrifugal force is used to mix and to transfer the discrete aliquots of sample(s) and reagent(s) into their respective cuvets. The ensuing reactions are monitored photometrically, and the data are processed in real time by either a portable Data Processor [Clin Chem. 18, 762 (1972)] or an on-line computer. A major improvement to the analyzer has been the addition of a temperature-control system that allows the temperature of the spinning rotor to be monitored and controlled to within ±0.2°C. After completion of an analytical run, the rotor is automatically washed and dried in the rotor cleaning station. Many of the standard clinical analyses, including most of the NADH-linked enzymatic analyses, have been adapted for use with this system.

We have developed a centrifugal analyzer with both fluorescence/light-scatter and conventional absorbance optics. The instrument is used in this investigation to study the formation of antigen-antibody complexes by light scattering and turbidimetric measurements, and to develop assays for human immunoglobulins G, A, and M. Concentrations are calculated from a nonlinear least-squares fit of calibrators, and antigen excess is automatically detected from kinetic curve characteristics. Precisions and patients’ results are presented, and assay sensitivity and reliability in the detection of antigen excess are compared. We also investigated the effects of centrifugal force on complex formation. Both nephelometry and turbidimetry can be very satisfactorily adapted to centrifugal analyzers. We present a model to describe the observed differences between the light-scatter and the turbidity data.

A miniature Centrifugal Fast Analyzer has been modified for fluorescence and light-scatter measurements by using several rotors developed for this purpose. The modified system has been used to evaluate the feasibility of adapting specific protein analyses, such as IgG, IgA, IgM, C'3 complement component, and α-1-antitrypsin, to the Centrifugal Fast Analyzer. A study of reaction conditions has revealed that the addition of polyethylene glycol 6000 (Carbowax) to the dilution medium increases the rate of reaction and allows apparent equilibrium to be achieved in less than 60 s. Furthermore, scatter intensity is enhanced. This system can be used to make rapid immunoglobulin measurements with only microliter volumes of antibody (2-7 µl), without the need of sample blanks. Determination of antigen excess by a method that involves dynamic injection of antibody is also discussed.

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Serum triglycerides can be enzymatically determined by hydrolysis of triglycerides to glycerol and free fatty acids [Clin. Chem. 19, 476 (1973)]. Enzyme integral (end-point) and fixed-time rate analyses of serum triglycerides by this procedure have been investigated with a centrifugal analyzer. We determined the precision of blank determinations, the contribution of normal serum alkaline phosphatase to total values, and the amount of endogenous glycerol in fasting serum samples and blood collection tubes. We also made a statistical analysis of enzymatic triglyceride values obtained for a healthy, fasting (12-16 h) population of men and women. The relative merits of both procedures are discussed.