and incubation time only results obtained with BSA mem- Ž brane are presented because those obtained with PVA membrane are quite similar . Fig. 7a shows a range of . y3 detected concentration comprises between 10 M 0.26 g Ž y1. y6 Ž y1 l and 10 M 0.26 mg l which corresponds to the . values found in the literature 14,24 . To our knowledge, w x no exposure limits have been established for trichlorfon in water.