Desenvolvimento de um equipamento portátil e de sistema de análises em fluxo empregando multicomutação. Determinação fotométrica de ferro em águas de rios / Development of a portable equipment and a flow analysis system employing multicommutation. Photometric determination of iron in river waters

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

20/07/2011

RESUMO

Iron is the most abundant element on Earth and plays an important role in biogeochemical cycles. In this work, an automatic analytical procedure was developed for the photometric determination of iron in river waters, employing a LED-based photometer and solenoid mini-pumps for solution handling. The proposed procedure was based on the reaction between iron (III) and potassium thiocyanate, yielding a red complex with maximum absorption at 470 nm. For the determination of total iron, an in line oxidation step was included, employing a persulfate solution (S2O82-) as oxidant. The module was constructed with four solenoid mini-pumps and a three-way solenoid valve. For data acquisition a photometer was constructed with a 50 mm optical path flow cell, a blue LED (\ lâmbda\ = 470 nm) and a photodetector. Envisioning the use of this portable equipment in field, two 6-Volt batteries were employed to supply energy to the active devices. Laboratory tests showed that the batteries provide more than 50 hours of operation without recharging. The proposed procedure showed the following analytical features: linear response between 0.25 and 4.0 mg L-1, according to the equation Y = (0.0183 ± 0.003) + (0.15326 ± 0.002) X (r = 0.9997); detection limit of 0.013 mg L-1 Fe (III), estimated with 99.7 % of confidence; relative standard deviation estimated as 0.95% (n = 15), obtained with a 1.5 mg L-1 Fe (III) solution; sampling rate of 50 determinations per hour.The results obtained with the proposed and reference procedure did not show significative differences at a 95% confidence level

ASSUNTO(S)

natural waters solenoid mini-pumps spectrophotometry Águas naturais análises em fluxo espectrofotomeria ferro flow analysis fotômetro de led iron led photometer mini-bombas solenóide multicommutation multicomutação

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