A microflow analyzer with an integrated gas diffusion unit

Abstract

Este trabalho descreve o desenvolvimento de um micro-analisador de fluxo com unidade de difusão gasosa integrada. A fotolitografia profunda no ultravioleta foi empregada para gravar os canais (largura de 500 mm e profundidade de 440 mm) sobre duas placas de fotoresiste de uretana-acrilato (UA), e uma membrana de politetrafluoretileno (PTFE) foi adaptada entre as estruturas planejadas para a manipulação das soluções doadora e aceptora. Para a realização de medidas de condutividade, três pares de eletrodos (seis fios de cobre com 0,5 mm de diâmetro) foram acoplados ao sistema, através de canais-guia, ortogonais ao canal de detecção. O dispositivo microfluídico proposto apresentou um volume interno total de 48 mL e suportou vazões de até 1,0 mL min −1 sem vazamentos ou rompimento da membrana. Os sinais analíticos para a determinação de bicarbonato em águas minerais proporcionaram uma resposta linear (R 2 = 0,999) para a faixa de concentração estudada (20 a 80 mg L e RSD = 3,0% (n = 5)). As freqüências de amostragem para os procedimentos com HCO 3 − e NH 4 + foram 15 e 25 injeções h −1 , respectivamente. Para ambas as aplicações, os resultados foram concordantes com aqueles obtidos por titulações potenciométricas (HCO 3 − ) e espectrofotometria UV-Vis em batelada (NH 4 + ). Adicionalmente, utilizando-se vazões de 40 mL min −1 para as soluções aceptora e doadora, uma redução de aproximadamente 75% na geração de resíduos foi calculada ao se comparar o micro-analisador com um sistema de análise em fluxo convencional. Estes resultados demonstraram a viabilidade de se desenvolver micro-analisadores de fluxo com unidade de difusão gasosa e detecção condutométrica.This work describes the development of a microflow analyzer with an integrated gas-diffusion unit. Deep ultraviolet photolithography was employed to engrave the channels (width of 500 µm and depth of 440 µm) on two plates of urethane-acrylate (UA) photoresist, and a polytetrafluoroethylene (PTFE) membrane was adapted between the structures designed for manipulation of donor and acceptor solutions. To perform the conductivity measurements, three pairs of electrodes (six copper wires with 0.5 mm diameter) were coupled into guiding channels, orthogonal to detection channel. The proposed microfluidic device presented a total internal volume of 48 µL and supported flow rates up to 1.0 mL min −1 without leakages or membrane damages. Analytical signals for the determination of bicarbonate in mineral waters provided a linear response (R 2 = 0.999) for the concentration range studied (20 to 80 mg L −1 ), a limit of detection (LOD) of 2.3 mg L −1 and a relative standard deviation (RSD) of 2.5% (n = 5). A similar performance was observed for the determination of ammonium in medicinal tablets (R 2 = 0,998 (10-40 mg L −1 ), LOD = 2.9 mg L -1 and RSD = 3.0% (n = 5)). The sampling rates for HCO 3 − and NH 4 + procedures were 15 and 25 injections h −1 , respectively. For both applications, results agreed with those obtained by potentiometric titrations (HCO 3 − ) and UV-Vis spec...

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