Determination of Various Hemoglobin Species with Thermal-Lens Spectrometry

Desoxyhemoglobin, oxyhemoglobin, carboxyhemoglobin, methemoglobin, cyanohemoglobin, and hemichrome are determined using thermal-lens spectrometry, with the detection limits at the level of 10(-8) M/l (2-5 mcg/l depending on hemoglobin species). Signal behavior and detectability thresholds are in good agreement with theoretical modeling based on the approach proposed earlier by the authors to describe thermal-lens signal generation in complex (inhomogeneous) systems. The thermooptical response for all studied hemoglobin species depends on the power of laser radiation within the range of 1-50 mW (532, 514.5, and 488 nm). Under the conditions of a thermal-lens experiment, the total temperature growth (0.0001 K) due to heating of the studied solution as the radiation of the inducing laser is absorbed by hemoglobin is estimated. Due to the interference with oxyhemoglobin the error in determining desoxyhemoglobin using thermal-lens spectrometry (for a maximum radiation power of 532 nm, 210 mW) does not exceed 3% in the case when the ratio of the species is 10 :1. In the opposite case (determination of oxyhemoglobin in the presence of desoxyhemoglobin), the error does not exceed 5%, the ratio of test and interfering species being the same.