title: Determination of hematocrit based on diffusion of an inert molecular probe from agarose gels into whole blood.
abstract: 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 X 10(-3) delta A/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 X 10(-6) cm2 sec-1.
mesh_terms: D001786:Blood Glucose / Q000032:analysis; D004058:Diffusion; D005782:Gels; D006400:Hematocrit; D006461:Hemolysis; D006801:Humans; D008956:Models, Chemical; D011134:Polysaccharides; D012685:Sepharose; D012709:Serum Albumin / Q000032:analysis; D014805:Vitamin B 12 / Q000097:blood
chemical_list: D001786:Blood Glucose; D005782:Gels; D011134:Polysaccharides; D012709:Serum Albumin; D012685:Sepharose; D014805:Vitamin B 12