Movement of certain agricultural chemicals in soil was studied in the laboratory by measurement of the Ri values of monuron, diuron, bromacil, terbacil, and chloroneb on thin layers (400 p) of soil deposited on glass plates and developed in water, and by determination of the Freundlich isotherm constants (K) of these chemicals in soil-water systems. The relationship of the Freundlich constants (K) to the Ri values is discussed. An empirical equation relating these constants for the above agrichemicals on Keyport silt loam is shown to be K = (1 IRi -1) + 0.85.

Methods for determining benomyl, methyl 1-(butylcarbamoyl) -2-benzimidazolecarbamate, residue in plant and animal tissues and in soil involve isolation of the residue by extraction with an organic solvent, purification of the extract by a liquid-liquid partitioning procedure, conversion of the residue to 2-aminobenzimidazole, and final determination by direct fluorometric measurement or colorimetric analysis following bromination. Each method has a sensitivity of 0.1 p.p.m. based on a 50-gram sample. Average recoveries of about 87% have been obtained on all samples investigated, using both the fluorometric and colorimetric methods.

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A programmed temperature microcoulometric gas chromatographic method for determining terbacil (3-zm-butyl-5-chloro-6-methyluracil) residues in soil, plant, and animal tissues is based on the measurement of the intact molecule after it has been extracted from the sample with an alkaline solution and subsequently partitioned into an organic solvent.Bromacil (5-bromo-3-iec-butyl-6-methyluracil) can also be determined by the same procedure. The method has a sensitivity of about 0.04 p.p.m. based on a 25-gram sample, and an average recovery of better than 90% has been demonstrated on a variety of substrates.

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