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The determination of inorganic anions was very difficult until the development of ion chromatography (IC). The two techniques for performing the conductivity detection are 'single column' or 'non suppressed' IC and 'suppressed' IC. Non suppressed IC (NSIC) is generally the selected technique because of its simple instrumentation: with the addition of a conductivity detector, any standard HPLC system can perform NSIC.
Thus, according to the importance of IC, it is advisable the development of some IC experiments that could be integrated into existing laboratory courses in analytical chemistry. In this paper, the determination of phosphate in cola beverages by NSIC is introduced. Cola beverages are actually relatively rich in phosphoric acid, and may be considered as very suitable laboratory samples for the experiments.
In the practical session, each student analyzes at least 3 different colas, and calculates the phosphate concentration and its relative standard deviation from replicate injections of the same cola brand (Repeatability). From the students' reports, the instructor evaluates the reproducibility using the results obtained by different students for the same cola brands.
A relative difference among brands was detected in our experiments. The application of one-way-ANOVA to the collected results confirmed that the brands differ significantly.
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