Determination of acetone in breath

A light emitting diode (LED)-based photometric method for the measurement of gaseous acetone in human breath is presented. The detection chemistry is based on the reaction of acetone with alkaline salicylaldehyde to form a colored product, which absorbs in the blue and can be monitored with GaN-based LEDs with emission centered at 465 nm. Gaseous acetone in breath is sampled with a porous membrane based diffusion scrubber (DS). The collected sample in the continuously flowing water carrier reacts with the reagent solution. We have used two approaches to collect breath acetone: the use of a face mask and a Mylar balloon as a collection bag. With the face mask approach, the expired air can be measured over long periods without major subject discomfort, balloon collection (5 l) permits four measurements from a single fill. The LED-based liquid core waveguide (LCW) absorbance detector utilized sapphire ball lenses to prevent exposure of other optical components to a hot alkaline reagent solution. The high refractive index of the final mixture permitted the use of an inexpensive fluorinated ethylene copolymer (FEP Teflon®) tube as a 10 cm long LCW. The limit of detection (S/N = 3) is 14 ppbv gaseous acetone, and the linear range extends to 1.21 ppmv. The concentration range in 11 volunteer subjects ranged from 176 to 518 ppbv.