Direct vapor generation Fourier transform infrared spectrometric determination of ethanol in blood

A new procedure is proposed for a direct determination of ethanol in plasma and whole blood. The method is based on the injection of a discrete sample volume of 10 μl into an electrically heated Pyrex glass reactor in which, at a temperature of 90 °C, the ethanol is volatilized and introduced by means of a N2 carrier flow inside a long-path infrared gas cell and the corresponding flow analysis recording registered as a function of time. The measurement of the area of the flow injection recording, obtained from the absorbance of the transient signal in the range 1150−950 cm−1, allows the direct quantification of ethanol upto 2 g l−1, with a limit of detection of 0.020 g l−1 and coefficient of variation between 0.3 and 1.9% for three replicate analyses of the same sample. The analysis frequency of the method is 40 h−1, and it can be applied to a single drop of finger blood.