Simple and rapid determination of iodide in table salt by stripping potentiometry at a carbon-paste electrode

Abstract

A simple and rapid procedure, utilising constant-current stripping analysis (CCSA) at a carbon-paste electrode containing tricresyl phosphate as a pasting liquid (TCP-CPE), has been developed for the determination of iodide in table salt. Because of a synergistic accumulation mechanism based on ion-pairing and extraction of iodide in combination with electrolytic pretreatment of the TCP-CPE, the method is selective for iodide and enables direct determination of iodide in samples of table salt containing anti-caking agents such as K(4)[Fe(CN)(6)] (food additive "E 536") or MgO. The iodide content (calculated as KI) can be determined in a concentration range of 2 to 100 mg kg(-1) salt, with a detection limit (S/N=3) of 1 mg kg(-1), and a recovery from 90 to 115%. The proposed method has been used to determine iodide in several types of artificially iodised table salt and in one sample of natural sea salt. The results obtained agreed well with those obtained by use of three independent reference methods (titration, spectrophotometry, and ICP-MS) used to validate the CCSA method, indicating that the developed method is applicable as a routine procedure for rapid testing in salt production process control and in the analysis of marketed table salts.

Gold nanoelectrode ensembles for direct trace electroanalysis of iodide

“…The iodide concentration in the electrochemical cell, determined from triplicate analyses, was 1.6 ± 0.3 M. This value is smaller, but in acceptable agreement with the values of 2.1 M calculated from the iodide contents declared by the producer. Note that the iodine content declared for this kind of products is rather indicative; the initial amount of added iodide can, in fact, be lowered during storage as a consequence of partial volatilization following spontaneous oxidation of iodide to iodine [4,49]. The lower electrochemical reversibility of the CVs in these salt samples is probably due to other components, such as anticaking agents [50], which can be present in this rather complex sample.…”

Perspectives of Carbon Paste Electrodes in Stripping Potentiometry

“…One of such applications has already been proposed (determination of iodine in table 304 ANALYTICAL SCIENCES MARCH 2002, VOL. 18 salts 25 ) and it is believed that similar examples will appear soon. For this, however, we should to continue in the development and optimization of the individual methods, including those reported herein as hitherto preliminary assays.…”

Carbon paste electrodes in the new millennium

“…For instance, mixtures of this type have been employed in potentiometric indications, which is the case of carbon paste-based electrodes made of chemically active di-iso-nonyl phthalate (DINP [97]) or tricresyl phosphate (TCP [98]). The latter -when protonated in an acidic supporting electrode -is also applicable in electrochemical stripping analysis (ESA), acting as counter-ion for effective pre-concentration of some anions [99][100][101].…”

“…This was shown already in the first years of a new millennium; e.g., a former procedure elaborated for the determination of thallium [333] could be adapted for gold (as tetrachloroaurate [99,331]), or iodide [101,331], and the perspectives of stripping potentiometry with CPEs, focused on the role of pasting liquid, were thus outlined as quite promising; especially, for some determinations in samples with extremely complex matrices (e.g., iodide in non-pretreated and solely diluted urine [334]). As already shown in the previous section 3.4.1., another recently frequent application of CPEs in stripping potentiometry is their use as the electrode support for metallic films; the advantage of application being again that the electrode surface can easily be renewed compared to metallic film electrodes on solid supports [244,247,249,[344][345][346].…”