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In Japan, the maximum residue limit and an analytical bulletin method for alachlor and pyriminobac-methyl were recently published. Because this method has some problems, such as many interfering chromatographic peaks for some residues in certain crops, time-consuming sample preparation, etc., we have developed an alternative method. In the bulletin method, pesticides are extracted with acetone, reextracted with ethyl acetate, partitioned with hexane–acetonitrile, cleaned up on a Florisil column, and quantitatively determined by gas chromatography with flame thermionic detector (GC-FTD). In the developed method, pesticides are extracted by supercritical fluid extraction and directly cleaned up with a trap column consisting of Extrelut and Florisil (acetone–n-hexane, 3 + 7, as the eluent) or Bond Elut SAX and PSA (acetone–n-hexane, 1 +1, as the eluent). The test solution was quantitatively determined by GC with mass spectrometry. Alachlor, pyriminobac-methyl, and 9 other chloracetanilide pesticides were studied. Average recoveries of spiked samples (0.1 ppm) were between 52 and 104% with the bulletin method and between 68 and 106% with the developed method. By using the Japanese bulletin method, 3 pesticides from Japanese radish could not be measured because of many interfering peaks on the GC–FTD chromatogram, even on selected-ion monitoring (SIM) chromatograms. On the other hand, by using the developed method, SIM chromatograms had fewer interfering peaks than did the Japanese bulletin method.

Modification of HPLC conditions for the determinations of raw materials, intermediates and subsidiary colors (organic impurities) in 5 kinds of food azo colors were studied in order to analyze them simply and rapidly. The organic impurities were determined by HPLC using L-column ODS and a gradient system (0.02 mol/L ammonium acetate solution for 10 min, and a gradient with a mixture of acetonitrile and water (7 : 3)). The organic impurities in 163 samples of azo colors subjected to inspection in fiscal year 1999 were determined under the proposed HPLC conditions. It was found that the contents of organic impurities in 163 samples were less than the limit of Japan's Specifications and Standards for Food Additives, 7th Edition.