Whole blood hematocrit was determined by an approach which depends on the diffusion of an inert probe, to which red blood cells are impermeable, from a small agarose gel into a stirred, much larger blood sample. Blood cells influence the diffusion rate of the probe by, on the average, physically blocking a fraction of the gel surface. The blocking effect increases with the hematocrit. Cyanocobalamin (B-12) was found to be a suitable probe because it did not penetrate, bind to, or lyse blood cells and was not bound by plasma solutes. The loss of B-12 from gels in contact with blood was monitored by determination of the absorbance change at 540 nm of gels which had been quickly rinsed. The visible spectrum of B-12 in agarose gels was identical to the spectrum in water. Beer's Law was obeyed in 1-mm thick agarose gels over a concentration range of 0.1–0.8 mM. Based on the results from 48 blood samples covering the hematocrit range 25–69, a least-squares line was generated with a slope, −3.46 × 10−3 ΔA/hematocrit unit, a Y intercept of 0.295, and a correlation coefficient of 0.971. The precision of the technique was ±9.7%. The assay was insensitive to mean corpuscular volume and sample volume as long as the latter was 50-fold larger than the gel volume. The diffusion coefficient for B-12 in 1% agarose gels was found to be 1.4 ± 0.2 × 10−6 cm2 sec−1. © 1983, All rights reserved.
CITATION STYLE
Malin, M. J., Mihalik, M. C., & Sclafani, L. (1983). Determination of hematocrit based on diffusion of an inert molecular probe from agarose gels into whole blood. Analytical Biochemistry, 129(2), 434–445. https://doi.org/10.1016/0003-2697(83)90574-2
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