Latent solid-phase extraction with thermoresponsive soluble polymers

The use of soluble thermoresponsive polymers to sequester or scavenge hydrophobic guest molecules from dilute aqueous solutions on heating is described. In these studies, a homopolymer of N-isopropylacrylamide was shown to sequester 46-83% of a soluble monochlorotriazine from 0.1-10 ppm aqueous solutions when heating above this polymer's lower critical solution temperature (LCST). Substitution of the reactive piperidine-containing 20:1 copolymer poly(N-isopropylacrylamide)-c-poly[N-4-(acrylamidomethyl)piperidine] for this unreactive polymer led to >98% scavenging of these same triazines when heating above this reactive polymer's LCST. The monochlorotriazine guests studied included the herbicide atrazine and two dye-labeled analogues of this herbicide. In one case, an atrazine analogue was designed so as to contain a dansyl group for fluorescence analysis. In the second case, an atrazine analogue was labeled with a methyl red group to facilitate visual and spectrophotometric analysis. Atrazine concentrations were measured with liquid chromatography-mass spectrometry. The enhanced efficiency of the reactive piperidine-containing copolymer scavenger in removing triazines from solution is attributed to covalent bond formation by nucleophilic aromatic substitution of the chlorine of the monochlorotriazines by the piperidine nucleophile on the copolymer. (C) 2004 Wiley Periodicals, Inc.