Electrochemical Determination of Inorganic Contaminants in Automotive Fuels AndrØ L. Santos , a Regina M. Takeuchi, a Rodrigo A. A. MuÇoz,* b Lfflcio Angnes , c Nelson R. Stradiotto d a Universidade Federal de Uberlândia, Faculdade de CiÞncias Integradas do Pontal, 38304-402, Ituiutaba, Minas Gerais, Brazil b Universidade Federal de Uberlândia, Instituto de Química, 38400-902, Uberlândia, Minas Gerais, Brazil c Universidade de S¼o Paulo, Instituto de Química, 05508-000, S¼o Paulo, S¼o Paulo, Brazil d Universidade Estadual Paulista, Instituto de Química, 14800-900, Araraquara, S¼o Paulo, Brazil *e-mail: raamunoz@iqufu.ufu.br Received: April 13, 2012; & Accepted: May 24, 2012 Abstract This article critically reviews the electroanalytical methods developed for the determination of inorganic contami- nants in automotive fuels. Topics include the methods applied to the analysis of liquid biofuels and liquid fossil fuels for which different strategies were developed based on analytes and sample matrices. Special attention is given to electrodes, detection techniques, and sample preparation protocols (when required). Analytes include anions such as chloride, sulfate and phosphate, and mainly metallic species such as sodium, potassium, magnesium, calcium, cad- mium, copper, iron, lead, manganese, mercury, nickel, platinum, tin, vanadium, and zinc. Suggestions for future re- search are also presented. Keywords: Biodiesel, Bioethanol, Gasoline, Inorganic species, Electrochemical methods DOI: 10.1002/elan.201200193 1 Introduction The demand for energy is constantly increasing in order to supply commercial, agricultural and industrial activities of the modern society. The diminishing petroleum re- serves and increasing concerns regarding environmental pollution caused by fossil fuel emission has pressed the development of cleaner and renewable sources of energy. In this context, biofuels play a key role for the develop- ment of a sustainable society. The term biofuel refers to solid, liquid or gaseous fuels produced from biomass. Un- doubtedly bioethanol and biodiesel are the most used bi- ofuels which have partially replaced fossil fuels, such as gasoline and diesel oil. The US Department of Energy has set an ambitious goal of replacing 30 % of the liquid petroleum transportation fuel with biofuels by 2025 [1]. Similarly, the Brazilian Program of Production and Use of Biodiesel established the use of 20 % of biodiesel in the biodiesel-diesel blend used as automotive fuel by 2020. On the other hand, not only fuel but also food sup- plies will need to massively grow in the next few decades due to the continuous increase in the world population, which require energy to power their lives. Thus the dis- cussion regarding the total replacement of fossil fuels by biofuels is still ongoing [2]. The quality control of biofuels as well as fossil fuels is of capital importance for their commercialization and market acceptation. Electroanalysis provides remarkable advantages for on-site analysis such as inherent miniaturi- zation, low-power requirements, minimal waste of sample and reagents, fast response, low cost, and elevated sensi- tivity [3]. In this way, the application of electroanalysis for the quality control of (bio)fuels offers tremendous promise for on-site measurements. This article presents the first critical review of electroa- nalytical methods devoted to fuel analysis. This review fo- cuses specifically on the electrochemical determination of inorganic contaminants in liquid biofuels and fossil fuels. Analytes comprise anions such as chloride, sulfate and phosphate, sulfur compounds, acids, and mainly metallic species such as sodium, potassium, magnesium, calcium, cadmium, copper, iron, lead, manganese, mercury, nickel, platinum, tin, vanadium, and zinc. Additionally, gasoline additives (organometallic compounds) are included. Or- ganic contaminants will be addressed in a future review because of the large number of articles related to this topic. The different strategies developed for fuel analysis based on analyte and sample matrices are discussed. A wide range of electroanalytical techniques have been em- ployed such as potentiometry, conductometry, and vol- tammetry. Hyphenated techniques such as capillary elec- trophoresis and ion chromatography coupled with electro- chemical detectors have also been reported for fuel analy- sis. Electroanalysis 2012, 24, No. 8, 1681 – 1691  2012 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim 1681 Review