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FIA potentiometric system based on periodate polymeric membrane sensors for the assessment of ascorbic acid in commercial drinks
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Orientador(es)
Resumo(s)
Ascorbic acid is found in many food samples. Its clinical and technological importance demands an easyto-
use, rapid, robust and inexpensive method of analysis. For this purpose, this work proposes a new flow
procedure based on the oxidation of ascorbic acid by periodate. A new potentiometric periodate sensor
was constructed to monitor this reaction. The selective membranes were of PVC with porphyrin-based
sensing systems and a lipophilic cation as additive. The sensor displayed a near-Nernstian response for
periodate over 1.0x10-2–6.0x10-6 M, with an anionic slope of 73.9 ± 0.9 mV decade-1. It was pH independent
in acidic media and presented good selectivity features towards several inorganic anions. The
flow set-up operated in double-channel, carrying a 5.0x10-4 M IO-
4 solution and a suitable buffer; these
were mixed in a 50-cm reaction coil. The overall flow rate was 7 ml min-1 and the injection volume 70 µl.
Under these conditions, a linear behaviour against concentration was observed for 17.7–194.0 µg ml-1,
presenting slopes of 0.169 mV (mg/l)-1, a reproducibility of ±1.1 mV (n = 5), and a sampling rate of ~96 samples h-1. The proposed method was applied to the analysis of beverages and pharmaceuticals.
Descrição
Palavras-chave
Periodate Ascorbic acid Potentiometric sensors Flow injection analysis (FIA) Flavoured waters
Contexto Educativo
Citação
Editora
Elsevier