Determination of substituted ureas and some related herbicide residues in soils by gas chromatography

Abstract

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%.

Search for linuron residues in tributaries of the Chesapeake Bay

“…A number of methods can be found in the literature for the analysis of linuron by gas chromatography. Some of these (Baunok and Geissbuehler, 1968; Caverly and Denney, 1978; Glad et al, 1978) include reaction of the compound to form a volatile derivative while others (Khan et al, 1975;Lawrence, 1976b;McKone, 1969; McKone and Hance, 1968; Onley and Yip, 1969) measure linuron directly without derivatization.…”

Detection and Degradation of Linuron in Organic Soils

“…After evaporation to near dryness, the residue in each flask was redissolved in spectrophotometric grade methanol and filtered through glass filter paper to remove florisil and glasswool fragments. Ten microliters of each fraction was then injected into the injection loop of the high pressure liquid chromatograph 3 • Parameters of operation were as follows: Column -ODS -HC -SIL -X -I, mobile -60% (v/v) methanol in water [0.6% (v/v) ammonia] , flow rate -1 ml/min, pressure -6900 kPa, detection wavelength -254 nm. Peaks obtained were compared with those of standards of the four compounds.…”

“…Most of the methods for the physical analysis of linuron and other phenylureas have involved gas chromatography either directly (16,21,22,24), or indirectly through the formation of derivatives (2,3,8,9,18). The major problem encountered in the direct gas chromatographic analysis of unchanged phenylureas has been decomposition of the column (8).…”

“…The major problem encountered in the direct gas chromatographic analysis of unchanged phenylureas has been decomposition of the column (8). If certain derivatives of the parent compounds (2,18) or their corresponding anilines (3,9) are formed, they become thermally stable and decomposition on the column is avoided. Many researchers have never been totally satisfied with these techniques because they are often long and involved and, until recently (8), could only be used to distinguish between phenylurea parent herbicides.…”

Supercritical fluid extraction of s-triazines and phenylurea herbicides from sediment

“…Again, common extraction methods for these compounds from soil and sediment are solvent-and laborintensive and have limited selectivity (11), making the development of an improved alternative method of extraction desirable. Of the pollutants mentioned above, atrazine, simazine, isoproturon, and chlorotoluron have been found frequently in surface waters and, to a lesser extent, in groundwaters (12,13) and are likely to be found in soils and sediments. Supercritical fluid extraction (SFE) has been used for many years to extract components of interest from bulk materials in process engineering (14,15) and is currently emerging as a viable alternative to the more traditional methods of analytical-scale sample preparation (16,17), such as Soxhlet extraction.…”