Volumetric Titrations Using Electrolytically Generated Reagents for the Determination of Ascorbic Acid and Iron in Dietary Supplement Tablets: An Undergraduate Laboratory Experiment

Abstract

An undergraduate laboratory experiment for the volumetric quantitative analysis of ascorbic acid and iron in dietary supplement tablets is presented. Powdered samples of the dietary supplement tablets were volumetrically titrated against electrolytically generated reagents, and the mass of dietary reagent in the tablet was determined from the volume of potassium hydrogen phthalate solution used as a primary standard. Proposed electrolysis cell was directly powered by a 9 V battery eliminating the requirement of a coulometer. Students use this method to quantify the active ingredient in dietary supplement tablets: iron and ascorbic acid (vitamin C). The experiment is suitable for the undergraduate quantitative analysis laboratory.

Analytical Capabilities of Coulometric Sensor Systems in the Antioxidants Analysis

“…Taking into account the different strengths of the titrants-oxidants, there is the possibility of controlling the selectivity of the target analyte response. Thus, electrogenerated iodine does not oxidize phenolic AOs [55] and retinol [63], while it reacts with thiol-containing AOs [47][48][49][50][51] and ascorbic acid [55,59,60]. On the contrary, hexacyanoferrate(III) ions easily interact with phenolic AOs and ascorbic acid [55] but do not react with S-containing AOs.…”

All Roads Lead to Rome: Triple Stoichiometry with a Lithium Battery

“…To reinforce its concepts, experiments are continuously designed so that students can better understand molar ratios from a practical standpoint. For example, in the past decade, the Journal of Chemical Education published papers on the subject whereby the favorite techniques to ascertain stoichiometric relationships included mainly colorimetry/spectrophotometry, − conductivity, , electrochemistry, − gravimetry, − titrimetry, , gas generation, − thermochemistry/thermal analysis, , − and catalysis …”

Iodine Coulometry of Various Reducing Agents Including Thiols with Online Photocell Detection Coupled to a Multifunctional Chemical Analysis Station To Eliminate Student End Point Detection by Eye

“…Starch is used as the visual indicator when iodine is the electrogenerated titrant. 1,3,4,8,9 Twin polarized electrodes for biamperometric measurements have been used for cyclohexene, hydrazine, biologically active thiols, and carbimazole determina-tions. 6,7,10,11 Some authors have used two or more different end point determination methods to compare their precision.…”

“…Different titrants can be electrogenerated to determine electroactive species, acids and bases, and even complexing reactants. Iodine, bromine, hydroxide, and hydrogen ions have been reported in the literature. − These home-built instruments recommend either isolation of the anodic and cathodic electrodes or instrument simplification using nonisolated electrodes. ,, …”

“…For example, colorimetric end point determinations require the use of chemical indicators that signal the completion of the analyte reactions. Starch is used as the visual indicator when iodine is the electrogenerated titrant. ,,,, Twin polarized electrodes for biamperometric measurements have been used for cyclohexene, hydrazine, biologically active thiols, and carbimazole determinations. ,,, Some authors have used two or more different end point determination methods to compare their precision. Comparison of eye detection versus graphical analysis, potentiometry versus eye detection, potentiometry versus amperometry and eye detection, and spectrophotometry versus amperometry have all been published in this Journal and elsewhere. ,,− …”