Microsampling homogeneous immunoassay with Cedia digoxin reagents on the Technicon CHEM 1 chemistry analyzer.

We report the determination of digoxin concentration in serum with Microgenics Cedia digoxin reagents on the Technicon CHEM 1. The Technicon CHEM 1 clinical chemistry analyzer has a throughput of 720 tests per hour and uses only 7 microliters each of two reagents. A 100 test kit can perform 2,640 tests. The within-run coefficient of variation (CV) range is 2.3-0.9% and the total CV is 6.3-2.9% at concentrations tested ranging from 1.10 to 2.94 ng/ml. The results of the Technicon CHEM 1 (y) assay correlated well with those by the Technicon RA 1000 system (x) with 31 clinical serum samples (y = -0.03 + 1.11x, r = 0.96). We concluded that the Cedia digoxin assay on the Technicon CHEM 1 provides a very cost-effective, precise, rapid, and accurate means to determine digoxin concentration in serum.

Capsule chemistry technology for high-speed clinical chemistry analyses.

We describe a new analytical approach--"capsule chemistry"--for high-speed, selective analysis of a wide variety of analytes. Sequential micro-aliquots of sample and reagents are encapsulated within an inert fluorocarbon liquid. The resulting "test capsule" is introduced into a single analytical flow path, composed of a solid fluorocarbon, Teflon, where the sample is incubated, mixed, reacted, and measured as a moving series of individual tests. These randomly selective assays are processed at a rate of 720 per hour. The unique physical interaction between the liquid and solid fluorocarbon carrier materials effectively prevents detectable "carryover" of aqueous constituents between the successive test capsules. Reactions are monitored through the walls of the Teflon analytical channel at nine in-line detector stations for colorimetric and nephelometric measurements.

An innovative technology for "random-access" sampling.

A major instrumental limitation to rapid, "random-access" clinical analysis has been cross-contamination at sampling and reagent probes. Use of an immiscible, nonreactive fluid as a positive barrier between the liquid sample and reagent and the interior and exterior surfaces of their respective probes provides an inert, deformable surface that both prevents carryover and ensures accurate delivery. Being totally nonreactive under clinical chemistry conditions, the fluid does not affect the ensuing analysis. Application of this technology to the Technicon RA-1000 (trademark of Technicon Instruments Corp.) system allows transfer of a liquid sample and any of 14 liquid reagents to the reaction vessel with a carryover of less than 1/10(6) with a precision (CV) of 0.5%. Its use provides for a rapid analysis rate of 240 tests per hour, and for transfer of microliter quantities of serum, with carryover of less than 1/8000, again at an average CV of 0.5%.

Polychromatic analysis: new applications of an old technique.

As a means of correcting for many potential interferences, polychromatic analysis offers an effective alternative to either sample pretreatment or separate blank determinations. Because of the differing spectral characteristics of each interfering species, and the nature of these interferences (static vs. kinetic), the application of polychromatic analysis must be optimized for each analytical procedure to minimize all residual errors. Overall assay precision can be maximized by proper use of flagging procedure to minimize all residual errors. Overall assay precision can be maximized by proper use of flagging procedures (also based on polychromatic analysis). By using a second wavelength measurement, the analyst can also verify the accuracy of an analytical measurement in selected situations. These applications of polychromatic analysis are a departure from conventional analytical procedures in allowing for correction of various interferences in the actual reaction mixture, without making assumptions about the recovery of analyte during pretreatment or the equivalent absorptivity of interferent in both blank and assay solutions.