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A molecularly imprinted polymer (MIP) able to bind 4-nitrophenol (4-NP) was prepared using noncovalent molecular imprinting methods and evaluated as a selective sorbent in molecularly imprinted solid-phase extraction (MISPE) on-line coupled to a reversed-phase HPLC. It has been shown that the conditions chosen for washing the MIP and for eluting the analyte in the MISPE process are extremely important for ensuring good selectivity and recovery. River water samples, spiked with the 11 Environmental Protection Agency phenolic compounds at microgram per liter levels, were preconcentrated on-line using this MIP, and 4-NP was selectively extracted. The humic acid interference was simultaneously reduced considerably. The MIP was also compared with a commercially available highly cross-linked polymer (LiChrolut EN) and the former yielded cleaner extracts.

A new chemically modified polymeric resin, with an o-carboxybenzoyl moiety, is developed to be used in the on-line solid-phase extraction (SPE) of some pesticides and phenolic compounds from aqueous samples, in order to obtain better breakthrough volumes than other commercial sorbents. The chemical introduction of this moiety improves the efficiency of SPE by providing better surface contact with aqueous samples. This synthesized sorbent enables higher volumes of sample to be concentrated for determining polar compounds. When analyzing real samples, tap and river waters, different quantities of sulphite were added to decrease the initial band due to fulvic and humic acids. The matrix peaks decreased and there were no losses in the studied compounds observed when 500 and 1000 microliters of 10% Na2SO3 solution for every 100 ml of sample were added to tap and river water, respectively.