Spectrophotometric determination of sulphate in automotive fuel ethanol by sequential injection analysis using dimethylsulphonazo(III) reaction.

A sensitive SIA method was developed for sulphate determination in automotive fuel ethanol. This method was based on the reaction of sulphate with barium-dimethylsulphonazo(III) leading to a decrease on the magnitude of analytical signal monitored at 665 nm. Alcohol fuel samples were previously burned up to avoid matrix effects for sulphate determinations. Binary sampling and stop-flow strategies were used to increase the sensitivity of the method. The optimization of analytical parameter was performed by response surface method using Box-Behnker and central composite designs. The proposed sequential flow procedure permits to determine up to 10.0mg SO(4)(2-)l(-1) with R.S.D. <2.5% and limit of detection of 0.27 mg l(-1). The method has been successfully applied for sulphate determination in automotive fuel alcohol and the results agreed with the reference volumetric method. In the optimized condition the SIA system carried out 27 samples per hour.

[1]  F. Krug,et al.  Turbidimetric determination of sulphate in plant digests and natural waters by flow injection analysis with alternating streams , 1983 .

[2]  T. S. West,et al.  Kinetochromic spectrophotometry-II Determination of sulphate by catalysis of the zirconium-methylthymol blue reaction. , 1969, Talanta.

[3]  J. Moreira,et al.  The alcohol program , 1999 .

[4]  J. Lima,et al.  Multicommutation in flow analysis. Part 1. Binary sampling: concepts, instrumentation and spectrophotometric determination of iron in plant digests , 1994 .

[5]  K. Brunt.  Sulfate determination in industrial wastewater by liquid chromatography with postcolumn solid-phase reaction detection , 1985 .

[6]  Qin Zhang,et al.  Ethanol-diesel fuel blends -- a review. , 2005, Bioresource technology.

[7]  A. O. Jacintho,et al.  Emprego de reagente em suspensão em sistema de injeção em fluxo: determinação espectrofotométrica de sulfato em águas naturais , 2002 .

[8]  D. F. Boltz,et al.  Colorimetric Determination of Nonmetals , 1959 .

[9]  Johanna Smeyers-Verbeke,et al.  Handbook of Chemometrics and Qualimetrics: Part A , 1997 .

[10]  R. E. Taljaard,et al.  Determination of sulphate in natural waters and industrial effluents by sequential injection analysis , 1996 .

[11]  P. Haddad,et al.  Electrostatic ion chromatography using hydroxide solutions as mobile phase with suppressed conductivity detection , 1999 .

[12]  B. Dale,et al.  Global potential bioethanol production from wasted crops and crop residues , 2004 .

[13]  K. Ueno,et al.  Flow-injection spectrophotometric determination of sulphate ion with a barium chloranilate-cellulose reaction column , 1992 .

[14]  William S. Saint.  Farming for energy: social options under Brazil's National Alcohol Programme , 1982 .

[15]  R. Bock.  Textbook of the Quantitative Inorganic Analysis, von I. M. Kolthoff und E. B. Sandell. The MacMillan Co., New York. 1952. 3. Aufl. XV, 759 S., 131 Abb. Gebd. $ 6.50 , 1954 .

[16]  A. O. Rangel,et al.  Use of a single air segment to minimise dispersion and improve mixing in sequential injection: turbidimetric determination of sulphate in waters. , 2003, Water research.

[17]  B. Klein.  Microdetermination of sulfate. A colorimetric estimation of the benzidine sulfate precipitate. , 1944 .

[18]  J. H. Karchmer,et al.  The analytical chemistry of sulfur and its compounds , 1970 .