Bismuth Film Electrode as an Alternative for Mercury Electrodes: Determination of Azo Dyes and Application for Detection in Food Stuffs

Abstract

Bismuth electrodes were investigated and exhibit electrochemical properties similar to mercury electrodes but with much lower toxicity. An electrochemical application of bismuth film modified glassy carbon electrode for azo dyes determination was investigated. The plating step was optimized in order to achieve its analytical efficiency. A plating potential of À 0.9 V in a solution of 200 mg/L Bi(NO 3 ) 3 , 0.5 M HNO 3 for 100 s yields to a suitable electrode (in terms of stability and detection). Azo dyes such as azorubine (i.e., carmoisine, E122), amaranth (E123), ponceau 4R (i.e., new coccine, E124) and allura red (E129) were determined by differential pulse voltammetry in a NaCl solution in the concentration range of few ppm to 100 ppm. The reproducibility of the signal, characterized by the relative standard deviation, was found to be less than 5%, the detection and quantification limits were few mg/L. The influence of other food components on the signal was studied and the applicability was tested on real beverages samples.

A Decade with Bismuth‐Based Electrodes in Electroanalysis

“…Also, organic compounds were not omitted, when the corresponding reports announced possible determinations of 4-nitrophenol [111], formic acid [112], or a quintet of synthetic Azorubine dyes used as the "E-" food additives [102]. Organic pollutants were then the focus of two reports [123,125] on nitroguanidines (Thiamethoxam and Imidacloprid), cyanoimine (Acetamiprid), and a nitromethylene derivative (Nitenpyram).…”

Determination of Allura Red and Tartrazine in Food Samples by Sequential Injection Analysis Combined with Voltammetric Detection at Antimony Film Electrode

“…TheE pw as shift towardsm ore negative values with the increment of the pH value.Alinear relationshipw ith slopes values of À0.057 and À0.053 VpH À1 were obtained for Ta nd AR, respectively.T hese values indicatea n equal number of electrons and H + in the reaction, which is congruentw itht he reductiono ft he azog roup (ÀN=NÀ) to hydrazo species( ÀNHÀNHÀ) [ 13,15].I na ddition, the highest signal for AR was observeda tp H4.0;t his pH value allows determine Ta tl ess cathodic.Ap Ho f4 .0 (acetate buffer solution)w as therefore selected for subsequent analysis.…”

“…3Results and Discussion 3.1 Optimizationo fthe SIA-VD System AR and Th ave cathodicr esponses at glassy carbone lectrodes [12] and BiFE [13].T he electrochemical reduction of azo dyes at SbFE was evaluated initially using DPV in the pH range from 4.0-8.0, as shown in Figure 2 Figure 2B), with ac lear dependenceo np Ho ns ignal peak potential (E p ), was obtained. TheE pw as shift towardsm ore negative values with the increment of the pH value.Alinear relationshipw ith slopes values of À0.057 and À0.053 VpH À1 were obtained for Ta nd AR, respectively.T hese values indicatea n equal number of electrons and H + in the reaction, which is congruentw itht he reductiono ft he azog roup (ÀN=NÀ) to hydrazo species( ÀNHÀNHÀ) [ 13,15].I na ddition, the highest signal for AR was observeda tp H4.0;t his pH value allows determine Ta tl ess cathodic.Ap Ho f4 .0 (acetate buffer solution)w as therefore selected for subsequent analysis.…”

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Natural and synthetic dyes are added to food and beverages to improve the visuala ppearanceo ft he finalp roducts.S ynthetic dyes are commonly usedb ecause of their lower cost and higher stability towardl ight, oxygen and pH changes [1].A llura red (AR)a nd Tartrazine (T) are two azo dyes commonly that can be foundi nc ommon food products.However, they can cause allergic and intolerance reactions [2].T he Food and Drug Administration establish acceptable daily intakes of 7a nd 5mg/kg/day for AR and T, respectively [3].I nM exico,t he maximum limits in drinks are 300 mg L À1 for AR and 100 mg L À1 for T, individually and 100 mg L À1 as mixture [4].Azo dyes have high values of molar absorption coefficients,t hus spectrophotometry has been commonly applied to determine these compounds [5][6][7].O ther methods described for this purpose are high performance liquid chromatography [8],c apillary electrophoresis [9] and electrochemical techniques.C athodic voltammetry has been applied to determine azo dyes as ac onsequence of the reduction processo btained using mercury [10], modified carbon [11][12] and bismuth film electrodes [13]. Thea ntimony film electrode (SbFE)h as demonstrated to possess adequate analytical performance compares to bismuth and mercury films during analysis of inorganic ions by anodic strippingv oltammetry [14].R egarding the analysis of azo compounds by SbFE, it has been describedt he analysis of sulfasalazine in pharmaceutical formulation [15].

Nowadays al aboratory should be able to perform determinations of al arge number of samples in an accurate, reproducible,f ast and economicw ay.F low techniques and in particular Sequential Injection Analysis (SIA) has becomei sbecoming an important toolf or the automation of chemicalp rocedures [16].T he combination of SIA with voltammetric detection improves the sensitivity and reproducibility of the methoda sac onsequence of the highly controllable conditions provided by the flowing solutions.

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“…Azo dyes have high values of molar absorption coefficients,t hus spectrophotometry has been commonly applied to determine these compounds [5][6][7].O ther methods described for this purpose are high performance liquid chromatography [8],c apillary electrophoresis [9] and electrochemical techniques.C athodic voltammetry has been applied to determine azo dyes as ac onsequence of the reduction processo btained using mercury [10], modified carbon [11][12] and bismuth film electrodes [13]. Thea ntimony film electrode (SbFE)h as demonstrated to possess adequate analytical performance compares to bismuth and mercury films during analysis of inorganic ions by anodic strippingv oltammetry [14].R egarding the analysis of azo compounds by SbFE, it has been describedt he analysis of sulfasalazine in pharmaceutical formulation [15].…”