The electrochemical reduction of the dye Disperse Red-13 at a glassy carbon electrode in N,N-dimethylformamide was investigated. The dye was better determined using a mixture of DMF/Britton-Robinson buffer (1:1, v/v), which displayed a well-defined peak at −0.40 V vs Ag/AgCl due to reduction of the protonated nitro group. This method was successfully applied for electroanalytical determination of DR-13 via a very simple and inexpensive way. All of the differential pulse voltammetry parameters were optimized using a glassy carbon electrode modified with poly(glutamic acid) films. The electroanalytical method presented a linear response from 2.5 × 10 −7 to 3 × 10 −6 mol L −1 to DR-13 (r = 0.997), with a detection limit of 1.5 × 10 −8 mol L −1 and recoveries from 89.7 to 95.10% in water samples. The dye was successfully determined in the wastewater after pre-extraction in a solid-phase extraction cartridge.Disperse dyes consist of non-ionic low molecular weight organic compounds that are sparingly soluble in water. 1 They are widely used in the dyeing of synthetic hydrophobic fabrics such as polyester, cellulose acetate, and nylon, among others. 2 Most of these disperse dyes contain an azo group as chromophore. They also contain polar groups and dyes of small molecular size, which improve their aqueous solubility in some special conditions. 3 As in the case of other dyes, dispersion dyes fixation does not reach 100%, so part of the dye that is not bound to the fabric during the dyeing process is drained into the wastewater. Because these dyes are designed to be chemically and photochemically stable in the aquatic biota, their determination in the dyeing bath and in the wastewater effluent is relevant for monitoring of their occurrence in the environment and control of their waste.However, methods that are suitable for the analysis of environmentally significant levels are scarce, due to the low solubility of disperse dyes in water. In addition, the toxicologic and ecotoxicologic properties of this kind of dyes have been brought to attention in the literature. The main papers on the determination of disperse dyes are based on UV-Vis spectrophotometry with multivariate calibration, total organic carbon analysis, 4 capillary electrophoresis, and liquid chromatography with UV or mass spectrometry detection, 5 which all require long preconcentration time and/or cleaning steps as well as special procedures concerning column poisoning in chromatographic experiments.There are a number of previous works, which detected disperse dyes based on electrochemical methods. Zanoni et al. 6 used cathodic stripping voltammetry for determination of two anthraquinonebased chlorotriazine dyes (procion blue MX-R and cibacron blue 3GA) at a hanging mercury drop electrode. They revealed that the reduction of the anthraquinone moiety in these dyes obtained no peak in differential pulse voltammetric stripping mode, while the signal was present in linear sweep mode. They concluded that the anthraquinone moiety is reduced so rapidly that reduct...