Recovery of picloram and 2,4-dichlorophenoxyacetic acid from aqueous samples by reversed-phase solid-phase extraction.

Extensive preparation of samples before chromatographic analysis is usually the most time-consuming process in the determination of many organic compounds in environmental matrices. In the past, removal of some organic8 from aqueous ,mlution was commonly done by liquid/liquid extraction. However, the introduction of stable, covalently bonded reversed-phase sorbents now allows efficient removal of bydrophobic compounds from aqueous solution by adsorption anachromatographic support. Solid-phase extraction is not anew technique. However, the procedure is more convenient today because of the commercial availability of ancillary : quipment and prepackaged disposable adsorption cartridges ins variety of sorbents (I, 2). Solid-phase extraction on bonded-phase organosilica based mrbents is an emerging technology for the analysis of chemicals of environmental significance. Environmental applicalions of solid-phase extraction for organic pollutant determinations in water have included the isolation of cbloroI phenolics (3,4), azaarenes (5), priority pollutants (6, 7), PAH i and PCB’s (a), and the trace enrichment of oilor jet-fuel/ wntan+ated water (9, IO): Pestlade residue determmations in water by solid-phase extraction have been published for the insecticides lindane, : heptachlor, aldrin, endosulfan, dieldrin, DDT, and zolone (?I), sldicarb (12). and carbaryl (13, 14) and for the herbicides paraquat (25). paraquat and diquat (26), fluridone (17, la), : pyramn (19), 2,4-D, 2,4,5-T, and silvex (20), atrazine, simazine, ~ !,4-D, silvex, and 2,4,5-T @I), and certain triazines (22). A iwlid-phase extraction method for the analysis of endrin, h’ndane, methoxycblor, and toxaphene has been submitted @an alternative test procedure to the current EPA (Envi:ronmental Protection Agency) approved method (23). If : approved, the proposed technique would amend the National Primary Drinking Water Regulations to eliminate the liquid/liquid extraction step in the current USEPA test procei due for these four organocblorine pesticides, replacing it with /taolid-phase extraction technique. Comprehensive reviews ~danalytical procedures for pesticide analysis from water have jbeen published (24-26). In the procedure presented herein, the herbicides pi&ram (l.amino-3,5&trichloropicolinic acid) and 2,4-dichlorophenmyacetic acid (2,4-D) are recovered from aqueous samples ‘insolid-phase extraction un reversed-phase sorbents as an :dtemative to liquid/liquid extraction. Previously, solid-phase /atraction on reversed-phase sorbents was used to effect puGation of pi&ram-containing samples that bad first been aumtrated by partitioning with diethyl ether (6, 7). Current modification of earlier methods accomplishes both sample purification and sample concentration. While this report was in preparation, two solid-phase ex:&ion methods for chlorophenoxy acid herbicides, including /2,4.D, were published by Hake et al. (20) and Sherma (22). ~However, neither of these procedures included pi&ram and itbereby did not address samples that could contain both /picloram and 2,4-D. i In this report, differential elution from the bonded-phase jsorbent is used to cleanly separate pi&ram and 2.4-D from