Novel Instrumental Approach to the Measurement of Total Body Water: Optothermal Detection of Heavy Water in the Blood Serum

The optothermal window (OW) in conjunction with a low-power infrared source was used at 4 μm wavelength to measure the concentration of D2O needed to determine the total body water (TBW) in human subjects. The 30 ppmv D2O detection limit is comparable to that obtainable by infrared transmission (IRT) spectroscopy but can be further enhanced. Low cost and ease of sampling and operation are other advantages of the novel method.