Near Infrared Analysis of Whole Blood and Plasma in Blood-Collecting Tubes

Abstract

An easy-to-use measurement method requiring no cleaning between samples, was developed and applied for the determination of cows' plasma constituents. Whole blood and plasma samples were measured with blood-collecting tubes as sample cells, providing easy sample handling and presentation. For whole blood, near infrared (NIR) spectra in the short wavelength region from 600 to 1000 nm were recorded with a portable NIR instrument (Fruit Tester 20: FT20). Plasma samples were measured in both the short wavelength region with the FT20 and in the long wavelength region from 1100 to 2500 nm with an NIRSystems 6500. Both instruments were equipped with specially designed sample holders for blood-collecting tubes and fibre optics. Partial least squares (PLS) regression was applied to derive calibrations for total protein, total cholesterol and glucose. Whole blood showed inferior performance to plasma because of scattering interference and absorption by red blood cells. Plasma results heavily depended on the constituent analysed. Total protein was determined accurately in both wavelength regions due to its high concentration and high absorptivity. For total cholesterol, the long wavelength region provided much better results because of its higher absorptivity. Results for glucose were only mediocre in both regions as its concentration and absorptivity were low. Overall, results indicate that blood-collecting tubes can be easily and effectively used for quantitative analysis of major constituents in blood plasma.