A method for the determination of 11 substituted ureas and related herbicides in soils is described. Acetone extraction is followed by alkaline hydrolysis, steam distillation and concentration of anilines in toluene, the last three steps being carried out in a single operation using a liquidliquid extractor. The anilines, after partition into hydrobromic acid, are brominated and determined by gas chromatography with an electron-capture detector. The procedure is sufficiently sensitive for investigations into problems of crop damage and can be applied to a wide variety of soil types. An additional step to remove interference due to the presence of aniline metabolites is also described. The limit of detection is 0.01 mg kg-l and recoveries a t residual levels are generally better than 80%.

Gasliquid chromatography provides a method of extreme sensitivity for the detection and determination of organochlorine pesticides residues. A single retention-time cannot, however, be regarded as a reliable identification of an unknown compound. A "clean-up" procedure is described by which interference is virtually eliminated, and a technique is proposed in which the change in retention-time after simple chemical reactions provides confirmation of the identity of a pesticide.

Rapid and sensitive techniques for the determination of residues of the fungicides furalaxyl and metalaxyl in agricultural samples are described. Air-dried soils and peat composts are extracted with acetone in a Soxhlet apparatus; the extract is applied directly to the gas chromatograph and detected using a nitrogen-selective detector. Plants are macerated with acetone and, after filtration and dilution with water, partitioned with chloroform ; nutrient solutions are similarly extracted with chloroform. The extracts are subjected to gas chroniatography after removal of chloroform and dissolution in acetone. Recoveries are generally better than SOY0 with detection limits of 0.5 mg kg-1 for peat, 0.1 mg kg-l for soils and plants and 0.02 mg kg-1 for nutrient solutions.

A rapid and sensitive procedure for the determination of residue levels of three uracil herbicides in soils is described. After addition of calcium hydroxide and Celite to the soil the herbicides are eluted from columns with water. After acidification of the eluate and partition into chloroform these herbicides are determined by gas chromatography using a nitrogen-selective detector.Recoveries from a range of soil types are better than SO%, with a sensitivity limit of 20 ,ug kg-l.