Determination of the substituted pyrimidine pesticides ethirimol, dimethirimol, pirimiphos-methyl, pirimiphos-ethyl and pirimicarb in technical and formulated materials by gas chromatography
Gas chromatography can be used to determine the members of a group of substituted pyrimidines that comprises two systemic fungicides, ethirimol and dimethirimol; two insecticides, pirimiphos-methyl and pirimiphos-ethyl; and an aphicide, pirimicarb.
The two fungicides, ethirimol and dimethirimol, are hydroxy compounds, which are determined by gas chromatography with flame-ionisation detection after conversion into their volatile trimethylsilyl ethers. The remaining three compounds are determined directly without derivative formation. All separations are carried out on a column packed with 100 to 120-mesh Celite coated with 10 per cent. silicone elastomer. Depending upon the retention time of the compound to be determined, either n-octadecane or n-nonadecane is added as an internal standard. The procedures are applicable to the technical pesticides and to a range of formulated products.
The methods are sufficiently specific and accurate to be recommended for referee purposes, and their precision has been shown to be satisfactory for routine control.