SIMPLE REMOVAL OF HUMIC AND FULVIC-ACID INTERFERENCES USING POLYMERICSORBENTS FOR THE SIMULTANEOUS SOLID-PHASE EXTRACTION OF POLAR ACIDIC,NEUTRAL AND BASIC PESTICIDES

A styrene-divinylbenzene (St-DVB) sorbent with a specific surface area of ca. 1000 m(2) g(-1) packed in a disposable cartridge was investiga ted and compared with C-18 silicas and other St-DVB polymers such as t hose entrapped in Empore disks and the LC-grade PRP-1 or PLRP-S with s pecific surface areas around 500 m(2) g(-1). A much higher retention w as obtained for polar pesticides and acidic pesticides were also retai ned in their ionic form. The recoveries obtained on percolating 500 mi of drinking water samples at pH 7 spiked with a mixture of seventeen acidic, neutral and basic pesticides through a cartridge packed with 2 00 mg of SDB-1 sorbent (1060 m(2) g(-1)) were above 80% for each analy te. Another important result was that humic and fulvic acids were not co-extracted and co-eluted on percolating a sample adjusted to pH 7, s o no clean-up was necessary. Application to the analysis of a 500-ml r iver Seine water sample spiked at 0.1 mu g l(-1) showed that detection limits in this range can be obtained without any additional clean-up step.