Continuous determination ascorbic acid by photobleaching of methylene blue

Abstract

The photolysis of a flowing stream to produce a reactive titrant has been reported (7). It was found that a solution could be completely or partially photolyzed with precision of 1 % or better (See Table II, Reference 7). However it was then necessary to add the photolyzed solution to a batch sample; this is cumbersome and time consuming for routine

Dye-sensitized continuous photochemical analysis. Identification and relative importance of key experimental parameters

“…We have previously reported the continuous determination of ascorbic acid (AA) by sensitized photooxidation with Methylene Blue (MB) (9). There exists an extensive literature detailing similar dye-sensitized reactions (6,(10)(11)(12)(13)(14)(15); most experiments were carried out batchwise in Warburg apparatus.…”

“…Although a study of the MBIAA system showed DCPA to have analytical potential ( 9 ) , it became clear that better understanding of the interactions between the photochemistry and operating conditions for DCPA was badly needed. The following objectives were selected for the present work: first, identify and evaluate those experimental parameters which have a significant effect on rate and extent of dye photobleaching reactions; second, determine whether experimental parameters for one given dye-sensitizer vary with the substrate photooxidized; third, develop guidelines for future study of dye-sensitized reactions to be tested for DCPA.…”

Flow Analysis: Looking Back and Forward

“…About 20 years after the inception of SCFA and following the proposals of some approaches involving unsegmented flows, 26,27 the term flow injection analysis (FIA) was coined by Ruzicka and Hansen. 28 They also established the fundamentals of FIA and jointly with other co-workers demonstrated several of its potentialities to large scale chemical analysis.…”

Informações essenciais para a caracterização de um sistema de análise em fluxo

“…Foram também apresentadas propostas explorando a segmentação por diferentes gases ou solventes. A viabilidade do emprego de um sistema de fluxo não-segmentado tornou-se evidente nos anos 70 7,10,[16][17][18] : os sistemas de fluxo sem segmentação apresentaram um aumento na versatilidade 19 , e o termo "análise por injeção em fluxo" ("flow injection analysis") foi proposto por Ruzicka e Hansen 10 . Além dos analisadores baseados em injeção em fluxo, outros sistemas de fluxo baseados em fluidos não-segmentados têm sido propostos 12,13,[20][21][22][23][24] e a versatilidade é, em geral, uma conseqüência do fluxo não-segmentado.…”