Relocation of a Tubular Voltammetric Detector for Standard Addition in FIA

Abstract

In this work a new strategy for the automation of the standard addition method by FIA with voltammetric detection is described, based on the concept of multi‐site detection. In the system developed, a single voltammetric detector with mobility in the FIA manifold, carried out sequential measurement of the sample plug before and after addition of the standard solution. The construction and evaluation of the voltammetric detector of tubular configuration and internal diameter similar to the tubing of the FIA manifold, whose incorporation in the system allowed the measurement process to be carried out without change of the hydrodynamic characteristics of the sample plug, is also mentioned. To evaluate the usefulness of the proposed multi‐site voltammetric detection system, this was used in the amperometric determination of ascorbic acid in fruit juices where the standard addition method is frequently required to overcome the matrix effect. The results obtained with the FIA system were compared with those from the reference procedure proposed by AOAC. No statistical difference between methods was found at the 95% confidence level. The relative deviations between both methods were always less than or equal to 3.8%. The sampling rate was about 55 samples per hour (110 measurements).

Kinetic method for acetylsalicylic acid determination based on its inhibitory effect upon the catalytic decomposition of H 2 O 2

“…The method was tested on commercial-available tablets, mentioned above, and the recovery of ASA, by the kinetic method, was between 98.4 and 101.4%. The detection limit of the proposed kinetic method may be competitive with those of spectrophotometric [12,14,15] or potentiometric methods [20,21] meant for pharmaceutical or medical applications, but not with those of amperometric [26,27,28] or chromatographic [18,19,20,21] methods. Simultaneous determination of 3-4 compounds, possible using chromatographic [18,19,20,21] methods, cannot be performed with this kinetic method, but it does have the advantages of relatively fast response, uncomplicated determination of ASA, and low cost of instrumentation, and so may be used for routine determination of ASA in drugs.…”

“…Acetylsalicylic acid (ASA) is probably one of most highly consumed drugs in the world, and many methods have been developed for its determination, including spectrophotometric [12,13,14,15,16], spectrofluorometric [17], chromatographic [18,19,20,21], potentiometric [22,23,24,25] and amperometric methods [26,27,28]. Chromatographic methods reach high performances and have the important advantage of permitting the simultaneous, accurate determination of several compounds, although they need expensive instrumentation.…”

Sequential Injection Anodic Stripping Voltammetry at Tubular Gold Electrodes for Inorganic Arsenic Speciation

“…Tubular configuration provides minimal flow disturbance and a higher contact area, compared with thin-layer configuration. This feature has enabled the application of tubular configuration in flow injection systems with sequential determination in which the detector is relocated inside the flow manifold (Catarino et al, 2002).…”

Automatic Determination of Uric Acid in Urine in a FIA System with a Tubular Amperometric Detector

“…On the one hand, voltammetric detection enables elevated levels of sensitivity and selectivity to be achieved and, on the other hand, the flow systems permit automation, making viable rapid, reproducible and relatively inexpensive determinations [12][13][14].…”

“…Previous work already demonstrated the efficacy of amperometric detectors of tubular configuration, coupled to FIA systems [11][12][13][14], namely in relation to the flexibility of the whole automatic system and the possibility of a rigid fixing to the manifold, conferring it with an elevated degree of robustness.…”