However, it is also important to evaluate how the FIA method compares with the standard Monier-Williams method. For this purpose, the results obtained for identical samples of concentrated cashew and

grape juices and coconut water were carried out and shown in Table 1. It is interesting to note that the free sulphite content in all samples was found to be within the range established by the Brazilian legislation. Concentrated cashew juices with high pulp content, traditionally showing much higher sulphite concentrations, ZD6474 were found to be within acceptable limits. Sulphite contents as high as 200 ppm were determined for the cashew juice samples, but was below 15 ppm in concentrated grape juices. In fact, in two this website of the analysed samples the sulphite concentration was below the detection limit of the M-W and of the FIA method. The low concentration of sulphite in grape juices, close to the limit of the M-W method estimated as 10 ppm, may be responsible for larger errors and higher differences in those measurements, since excellent signal to noise ratio and reproducible results were obtained for the FIA analyses. It is important to notice that the samples used in the analyses shown in Table 1 are different from those used in all other experiments. The average of three measurements and the respective deviation (in

parentheses), as well as the ratio of the respective standard injection FIA and M-W method analyses are listed. In general, the results of the FIA method compared well with that of M-W method. For instance, the cashew juice with high solid content gave very similar results for both methods, suggesting that amperometric FIA method is

suitable for the free sulphite content analyses. However, higher concentrations Florfenicol were consistently determined by FIA in comparison with the M-W method, probably due to the lower influence of the oxygen in air during the manipulation of the samples. In fact, oxygen tends to react with sulphite decreasing its actual amount. To overcome this problem, the samples were carefully prepared avoiding contact with air; and the FIA analyses were carried out in minutes, providing an interesting alternative to the M-W method. The new compact system, integrating a gas diffusion unit and a wall-jet amperometric FIA detector using a glassy carbon electrode modified with supramolecular tetraruthenated porphyrin, allowed fast, reproducible and accurate analyses of free sulphite content in concentrated juice samples. Two different ways of analysis were examined: one based on the direct injection of a standard sample as reference followed by the injection of the real sample; and another involving the injection of the real sample alone and with increasing amounts of a standard solution.