Rapid discrimination of oils containing coumarin using three-layer extraction and fluorescence spectrometry.

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  • KURATA Shoji
    Criminal Investigation Laboratory, Metropolitan Police Department
  • AIZAWA Naoyuki
    Criminal Investigation Laboratory, Metropolitan Police Department
  • HIRANO Haruo
    Criminal Investigation Laboratory, Metropolitan Police Department
  • NAGAI Masatoshi
    Graduate School of Bio-applications and Systems Engineering, Tokyo University of Agriculture and Technology

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Other Title
  • 三層分離抽出／蛍光分光光度法によるクマリンを含む油類の簡易識別分析
  • 技術論文 三層分離抽出/蛍光分光光度法によるクマリンを含む油類の簡易識別分析
  • ギジュツ ロンブン 3ソウ ブンリ チュウシュツ ケイコウ ブンコウ コウドホウ ニ ヨル クマリン オ フクム ユルイ ノ カンイ シキベツ ブンセキ

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Abstract

Three-layer extraction followed by fluorescence spectrometry has been developed for the rapid discrimination of oils containing coumarin. The proposed method provides facilities, such as rapidity, convenience, and down-sizing. The procedure of the method is as follows: 0.25 ml of oil samples was used for quantification. After shaking a mixture of the sample with 1.5 ml of dodecane, two ml of butanol-ethanol (4:3; v/v) solution, and 1.25 ml of alkaline aqueous solution (2.5 M NaOH) for three min, non-fluorescing o-coumarinate ions produced from coumarin by hydrolysis were extracted in an alkaline aqueous solution. Fluorescent compounds in oils were extracted together with the o-coumarinate ions in the alkaline aqueous solution, and interfered with the quantification of the o-coumarate ions using fluorescence spectrophotometry. The addition of inorganic salts to the alkaline aqueous solution was very effective to quench the fluorescent interference of the co-extracted substances from oils. The addition of sodium nitrate which was the most effective quencher, suppressed any unfavorable fluorescent interferences. After the o-coumarinate ions were converted into isomeric o-coumarate ions by the irradiation of ultraviolet light for five min, fluorescence intensities at 500 nm were measured. The fluorescence intensity showed a good linear relationship with the gas-oil content in the range of 5∼100% of fuel oil A in the gas-oil mixtures. A statistical analysis of the calibration curve gave an excellent relation with a correlation coefficient of 0.996∼0.999. The proposed method could successfully discriminate illegal diesel fuels containing coumarin.<br>

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 52 (3), 187-194, 2003

    The Japan Society for Analytical Chemistry

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