(725e) Optical Sensing of Acetone in Exhaled Breath Utilizing Acid Catalyst Membranes

Measurement of acetone content in human breath has been suggested as a non-invasive method to the diagnosis of diabetes and/or ketoacidosis. Existing methods employ time consuming, ex-situ analyses of breath condensate that limit broad, real-time application. In the present study, the diffusion and immobilization of dilute fluorescent dyes into the heterogeneous nanophases of perfluorosulfonic acid (PSA) polymer membranes is investigated for direct, one-step gas phase acetone analysis utilizing a hand-held device. The membranes act as acid catalysts for the condensation reaction of acetone and the immobilized dyes at temperatures above the acetone boiling point, yielding an optical response in the visible region of the electromagnetic spectrum that may be observed utilizing standard light emitting diodes (LED's). Partitioning of the dye concentration among the lipophilic, hydrophilic, and transitional nanophases within the PSA membrane is shown to control the sensitivity of the membrane to acetone exposure, down to ppb levels. UV/VIS and FTIR are utilized to quantify the diffusion of the dyes and acetone in the membrane. The use of deuterated acetone as a marker molecule allows for the determination of the intermediate and product molecules (flavans) immobilized within the membranes and to confirm the selectivity of the optical response.