Abstract Adsorptive stripping voltammetry was used for the determination of trace amounts of the dye Tartrazine (E-102) by square-wave (SWS) and differential pulse tech- niques (DPS). Its adsorptive voltammetric behaviour was investigated at different pH media. NH 4 Cl/NH 3 buffer so- lution was chosen as the most suitable, taking into account the sensitivity and definition of the reduction peaks ob- tained. The effects of the experimental parameters on the determination are discussed. Standard deviations of 3.3% and 2.6% were obtained by SWS and DPS for 100 and 50 μg/L Tartrazine solutions, respectively (n = 10). Both meth- ods were applied to determine the dye in several commer- cial soft drinks, containing very small amounts of it. Mea- surements were made directly in the commercial samples. A comparison of the results obtained by the proposed voltammetric methods with those of an HPLC method was also made. Good correlations between the voltammetric results and the values supplied by the manufacturer were found, whereas recoveries of the same order of magnitude were obtained by the HPLC method. Introduction Food colorants may often simply be considered as cos- metic in nature, but their role in food industry is actually very significant. Colour is the first sensory quality by which foods are judged and food quality and flavour are closely associated with colour. Consumers expect food of certain colours and reject any deviation from their expectations. The psychological basis for the need of food colours is well established [1]. Colorants also play a significant role in enhancing the aesthetic appeal of food. They are very important ingredi- ents in many convenience foods such as confectionery products, gelatin desserts, snacks and beverages, since many of these would be colourless and would thus appear unde- sirable. The term colour additive can be applied to any dye, pigment or other substance synthetically prepared (artifi- cial colorant) or obtained from a vegetable, animal, min- eral or other natural source, capable of colouring foods, drugs or cosmetics [2]. Tartrazine, subject of this work, is a synthetic dye available as yellow powder that can be present in common foods (drinks, yoghourts, ice cream, sweets, etc.). The content of this dye must be controlled because its presence and/or contact with some kinds of drugs (aspirin, benzoic acid and other analgesics) in the human body can induce allergic and asthmatic illness in sensitive people. This colorant had been included in a list of ingredients after an extensive study of the genotoxicity of drugs, foods and cosmetic colours realized by Have- land-Smith [3]. Recently, we have developed spectrophotometric meth- ods in order to determine this dye in three binary mixtures and a ternary mixture with three other yellow dyes [4–7]. These methods were applied to several commercial products. On the other hand, chromatographic methods have been previously used for colorant analysis in foods [8–11]. Fogg et al. have realized a theoretical and general study about the voltammetric behaviour of several synthetic col- orants (reduction peaks potentials and intensities) by means of DPP and DPS techniques [12, 13]. Tartrazine was not determined in any commercial product in both cases, since the study made was brief and theoretical. The sensitivities reached by Fogg et al. in the analysis of other dyes in commercial samples (tablet coatings and cosmet- ics) were smaller than those obtained by us in soft drinks. Due to the low contents of the dye in some commercial products, we have developed an adsorptive stripping volt- ammetric method, which is a very useful technique for the study and determination of low levels of compounds. In this work, an optimization of the experimental parameters to reach the best sensitivity in Tartrazine determination by SW or DP voltammetry has been achieved taking into ac- count the possible adsorption of the molecule (whose for- mula is given below) on the mercury and following the J. J. Berzas Nevado · J. Rodríguez Flores · M. J. Villaseñor Llerena Adsorptive stripping voltammetry of Tartrazine at the hanging mercury drop electrode in soft drinks Fresenius J Anal Chem (1997) 357 : 989–994 © Springer-Verlag 1997 Received: 23 May 1996 / Revised: 5 July 1996 / Accepted: 10 July 1996 ORIGINAL PAPER J. J. Berzas Nevado () · J. Rodríguez Flores · M. J. Villaseñor Llerena Department of Analytical Chemistry and Food Technology, University of Castilla-La Mancha, E-13071 Ciudad Real, Spain