| Development and characterization of a small-scale separator and a flow analyzer for near-patient clinical diagnostics is presented including: separator design and characterization, separator and analyzer integration, modeling of carryover in the analyzer, and instrument modifications made to expand capabilities to UV wavelengths.; The separator is designed for separation of plasma from whole blood for use in a point-of-care testing system. Sedimentation theory was used to optimize the chamber taper. Theoretical predictions indicate separation times of 37 to 28 sec for a taper angle of 16–20°, for 1–1.5 mL samples, which agrees to within 25% of experimental observations. Characterization included evaluation of hemolysis and cellular carryover. Hemolysis was determined to be negligible. Cellular content was reduced to 0.00063% after seven washes, and theoretically no carryover in 11 steps.; Integration of a separator, analyzer, and a sampling probe was characterized by evaluating hemolysis, cell pack volumes in plasma, and glucose recoveries. Hemolysis studies yielded statistically equal hemoglobin content in test and control samples. Cell pack in plasma was about 0.3% after 90 sec separations. Statistically, glucose recoveries were equal. Analyte carryover in the integrated system was determined to be negligible, but dilution of low concentration samples was observed.; Modeling carryover in the air-segmented continuous flow analyzer was investigated by describing the system as a series of continuously stirred tank reactors. An initial carryover flowrate of 0.087 μL/sec was determined from an experimental datum for a fully reacted reagent/sample pair. The carryover flowrate was adjusted to 0.114 μL/sec through residual analysis to improve agreement between numerical results and experimental observations for the system of boluses. Addition of kinetic rate expressions to the model allowed evaluation of varying scenarios of carryover with reaction. The model described 80% of the experimental data to within one standard deviation. Using the model, operating conditions that yield minimal carryover were identified, where at least five 16.4 μL boluses are needed to reduce carryover to <1%. Consequently, 6–8 chemistries can be processed in 6–8 minutes.; Modifications to the analyzer for UV measurements were evaluated using NADH solutions and a glucose hexokinase assay for glucose analysis. Results indicate a linear absorbance response for solutions analyzed, thus expanding capabilities to UV wavelengths. |
