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Exploiting gas diffusion for non-invasive sampling in flow analysis: determination of ethanol in alcoholic beverages

Author(s): Vicente Simone | Zagatto Elias A.G. | Pinto Paula C.A.G. | Saraiva Maria Lucia M.E.S. | Lima José L.F.C. | Borges Eduardo P.

Journal: Anais da Academia Brasileira de Ciências
ISSN 0001-3765

Volume: 78;
Issue: 1;
Start page: 23;
Date: 2006;
Original page

Keywords: Flow-injection analysis | ethanol determination | gas diffusion | semi-permeable membrane | UVVis spectrophotometry

A tubular gas diffusion PTFE membrane is exploited for non-invasive sampling in flow analysis, aiming to develop an improved spectrophotometric determination of ethanol in alcoholic beverages. The probe is immersed into the sample, allowing ethanol to diffuse through the membrane. It is collected into the acceptor stream (acidic dichromate solution), leading to formation of Cr(III), monitored at 600 nm. The analytical curve is linear up to 50% (v/v) ethanol, baseline drift is < 0.005 absorbance during four working-hours, and sample throughput is 30 h-1, meaning 0.6 mmol K2Cr2O7 per determination. Results are precise (r.s.d.< 2%) and in agreement with an official procedure.
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