Recebido em 29/11/01; aceito em 27/5/02 DEVELOPMENT OF A LOW COST DEVICE FOR CHEMILUMINESCENCE MEASUREMENTS. A simple and low cost device (ca. US$ 150) that comprises two photodiodes fixed in lab-made Perspex flow cell is proposed for chemiluminescence measurements. The characteristics of the device (large observation window and reduced thickness) allow maximizing the amount of the emitted radiation detected. A sensitivity improvement of ca. 50 % was observed by employing two photodiodes for signal measurements. The performance of the device was assessed by the oxidation of luminol by hydrogen peroxide, yielding a linear response within the range of 2.50 to 500 µmol L -1 H 2 O 2 . The detection limit was estimated as 0.8 µmol L -1 hydrogen peroxide which is comparable with those obtained by using equipments based on photomultipliers.
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 K 2 Cr 2 O 7 per determination. Results are precise (r.s.d. < 2%) and in agreement with an official procedure.
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