Square wave voltammetry (SWV) on carbon disk ultramicroelectrodes (UME) was used to determine antioxidants tert-butylhydroxyanisole (BHA) and tert-butylhydroxytoluene (BHT) in vegetable oils. Direct determinations were accomplished in benzene/ethanol/H 2 SO 4 solutions or in acetonitrile (ACN) after an extractive procedure. Much better recovery percentages were obtained in ACN extracts. By comparing with high-performance liquid chromatography (HPLC) results, BHA has a slightly lower recovery percentage by the SWV technique on ACN extracts. On the other hand, BHT shows a greater recovery percentage using the methodology proposed here. The analysis time through SWV is less than an hour for a duplicated analysis while the HPLC technique needs a greater time, besides the overnight stored time required by the current methodology. The present work tends to show that SWV on carbon disk UME allows sensitive, reproducible, and faster determination of BHA, BHT, or antioxidant mixtures in oil-solvent solutions or after a simple extractive procedure with the advantage of a higher recovery percentage. This validates the methodology as an analytical alternative for antioxidant quantification.Paper no. J9364 in JAOCS 77, 731-735 (July 2000).KEY WORDS: Antioxidant electroanalytical determination, BHA, BHT, carbon disk ultramicroelectrode, nonaqueous solvents, square-wave voltammetry, standard addition method, synthetic antioxidants, vegetable oils.During recent years, many articles claim the advantage of the use of electrochemistry in food process or analysis (1-5). In the analytical field, electrochemical techniques were used to determine and quantify phenolic compounds used as antioxidants (6-10). tert-Butylhydroxyanisole (BHA) and/or tert-butylhydroxytoluene (BHT) are the most common antioxidants used in the lipid industry to improve stability and prevent rancidity in their products (11-13). Thus, the identification and quantification of antioxidants play an important role in the quality assignment of lipid compounds.Both the AOAC (14) and AOCS Official Methods and Recommended Practices (15) include the determination of several antioxidants with acetonitrile (ACN) extraction step followed by high-performance liquid chromatography (HPLC) separation with ultraviolet (UV) detection at 280 nm.Electrochemistry on ultramicroelectrodes (UME) appears as a good alternative for electroanalysis, particularly for the quantification of synthetic antioxidants (16-21).On the other hand, pulse voltammetric techniques, especially square-wave voltammetry (SWV), have been proposed as alternative methods to decrease the time needed for analytical purposes (7,22). Thus, it is also possible to combine disk UME with SWV (23) to obtain highly reproducible signals, to minimize the cleaning difficulties of the UME and to improve both speed and sensitivity compared with other voltammetric methods (7,18,24).In this work, direct measurements of antioxidants on vegetable oil solutions as well as determinations after extraction steps followed by SWV detect...