A syringe-based sample pretreatment tool, named herein "tip-in chelating monolith", has been developed for simple and facile solid phase microextraction (SPME) of trace elements in natural waters. The tip-in chelating monolith was directly prepared within the confines of a commercially available syringe filter tip by a two-step process (1) in situ polymerization of a monomer solution consisting of 22 5% glycidyl methacrylate (GMA), 7.5% ethylene glycol dimethacrylate (EDMA), 35% 1-propanol, 28% 1,4-butanediol, and 7% water and (2) its subsequent modification with 1 mol L(-1) of iminodiacetate solution (adjusted to pH 10) via ring-opening reaction of epoxide The adsorption properties of the tip-in chelating monolith thus obtained were evaluated through an adsorption/desorption experiment, where the effects of sample solution pH and eluent on the SPME of trace metals and metalloids were systematically examined Consequently, when sample solution pH was adjusted to 50 and 09 mL of 2 mol L(-1) nitric acid was used as an eluent, good recoveries of more than 80% were obtained for 27 elements in a single-step extraction The proposed SPME method was validated through the analysis of two river water certified reference materials (CRMs JSAC 0301-1 and NMIJ 7201-a). After 50-fold preconcentration (from 50 mL of the original river water sample to 1.0 mL of final analysis solution), 22 trace elements including Ti. Fe, Co, Ni. Cu, Ga, Cd, Sn and REEs were quantitatively determined by inductively coupled plasma mass spectrometry (ICP-MS). The analytical detection limits were in the range from 0.000003 mu g L(-1) for Ho to 0 18 mu g L(-1) for Fe. Good agreement of the observed values with the certified or reference values indicates that the proposed SPME using the tip-in chelating monolith is practically applicable (C) 2010 Elsevier B V. All rights reserved