Analysis of phenylurea herbicides from plants by GC/MS

Seven phenylurea herbicides (chlorbromuron, fluometuron, diuron, linuron, metobromuron, monolinuron, monuron) were isolated from weed plant materials by extraction with acidic aqueous solutions-the aqueous extract preconcentrated and cleaned-up by using a continuous SPE module. Elution with ethyl acetate resulted in >95% recovery of the herbicides from the LiChrolut-EN sorbent column. Separation of the seven herbicides was easily achieved working under fixed gas-chromatographic conditions and, although other peaks were also detected (corresponding to isocyanate degradation products), they showed different retention times and lower intensity than the parent compounds, in addition, as reproducible chromatograms in terms of herbicide-to-isocyanate product peak areas ratio were obtained, no derivatization. was required. The analytical figures of merit of the GC/MS method in the selective ion monitoring mode are as follows: limits of detection from 0.5 to 5.0 ng ml(-1); precision (R.S.D.) approximate to 7.0%; and preconcentration factor 100 (using 10 ml of sample extract). The proposed GC/MS method offers better resolution and selectivity than the conventional LC-UV method. (C) 2002 Elsevier Science B.V. All rights reserved.