Determination of Methoxyphenone Residue in Crops by High-Performance Liquid Chromatography

Abstract

Residues of methoxyphenone (NK-049) in watermelon, tomato, carrot, rice grain and rice straw were extracted with acetone and partitioned into chloroform from an aqueous solution after distillation of acetone. Chloroform was distilled and the residues were cleaned up by two steps of column chromatography. Ten gram of silica gel was used as adsorbent of the first chromatography and methoxyphenone was eluted with 100 ml of benzene containing 5% of ethyl acetate after washing with 60 ml of benzene. On the second chromatography, 2 g of alumina containing 0.1 ml of 50% silver nitrate aqueous solution was added to the column of 10 g of Florisil. Methoxyphenone was eluted with 100 ml of benzene containing 5% of ethyl ether after washing with 100 ml of benzene. Then the residue was dissolved in 1 ml of methanol and 80 µl of the solution was injected into a high performance liquid Chromatograph fitted with a stainless steel column (4.6 mm · 25 cm) packed with Jasco, SC-02. The column was eluted with methanol and water (75 + 25) at a flow rate of 2 ml/min. The detector was UVIDEC-100 and the wavelength was 295 nm. The liquid chromatogram was much clearer than the gas chromatogram with ECD and no interfering peaks were observed in any samples. The lower limits of detection were 0.005 ppm (watermelon, tomato, carrot, rice grain) and 0.03 ppm (rice straw), so this method was as sensitive as ECD gas chromatography. The average recoveries of methoxyphenone were 88–93%. © 1980, Pesticide Science Society of Japan. All rights reserved.