Flow-injection spectrophotometric determination of ascorbic acid in pharmaceutical products with the Prussian Blue reaction

Spectrophotometric determination of ascorbic acid in grapes with the Prussian Blue reaction

“…Redox processes are generally involved in these determinations and it is possible to minimize air oxidation by using techniques such as flow injection (FI). One of these techniques is proposed by Nobrega and Lopes [12] and are mainly based on electroanalytical detectors due the inherent redox chemistry of the analyte and reagents. Optical FI methods also involve redox reactions with AA in which a colored compound is formed or decomposed.…”

A new, improved sensor for ascorbate determination at copper hexacyanoferrate modified carbon film electrodes

“…Shankaran and Narayanan [14] mechanically immobilised CuHCF on the surface of a graphite electrode and performed electrocatalytic oxidation of AA in 0.1 M NH 4 Cl using cyclic voltammetry. The oxidation peak of AA appeared at the same position that Cu + / Cu 2+ took place: the oxidation peak increased proportionally with the amount of AA in the solution.…”

“…Besides sensitivity and selectivity, stability is also a very important factor for the sensor. It is well known that Prussian Blue is unstable in neutral media [13,29], but the CuHCF film sensor is reported to be stable in slightly acidic medium (0.1 M NH 4 Cl solution) [14]. Its stability also depends on the deposition and operating conditions [13,[31][32][33][34][35].…”

“…Hexacyanoferrate(III) reacts with AA chemically in acidic medium [3] (see Scheme 1). This reaction is used to determine AA spectrophotometrically in pharmaceutical products [4][5][6].…”

Uso de scanner em espectrofotometria de absorção molecular: aplicação em experimento didático enfocando a determinação de ácido ascórbico

“…Esse procedimento foi adaptado por Nóbrega e Lopes em um sistema de injeção em fluxo com detecção espectrofotométrica. 2 A maneira mais comum de determinar a quantidade da substân-cia colorida é através do uso de espectrofotômetros que operam nas regiões do ultravioleta e visível do espectro eletromagnético. Esses equipamentos apresentam, basicamente, uma fonte contínua (por exemplo, uma lâmpada de tungstênio) que emite radiação, um monocromador para seleção de uma faixa estreita de comprimentos de onda que atingem a solução contendo o analito, um compartimento para posicionamento da amostra e um dispositivo para detecção da medida da intensidade de radiação.…”