Use of ELISA Immunoassay Kits as a Complement to HPLC Analysis of lmazapyr and Triclopyr in Water Samples from Forest Watersheds
The herbicide triclopyr (3,5,6-trichloro-2-pyridinyl)-oxyacetic acid has been marketed by the Dow Chemical Co. since the mid 1970's as the triethylammonium salt (Garlon 3A) and as the ethylene glycol butyl ether ester (Garlon 4). Shortly after its introduction, McKellar (1977) published a method for the extraction, isolation, and electron capture gas chroinatographic analysis of triclopyr and two of its major metabolites in soil and water samples. A number of environmental fate studies of triclopyr have been published since then, each of which has used the McKellar method or a minor modification of it (Oloffs et al. 1986; Deubert et al. 1986; Norris et al. 1987; Whisenant et al. 1989). Glas (1978) developed a method along similar lines for the analysis of triclopyr in plant tissues as did Bovey et al. (1983). While state-of-the-art for their day, these methods are labor-intensive and time-consuming. They use large volumes of dichloromethane which has been designated a hazardous material by the EPA, making its disposal difficult and expensive. These methods also involve derivitization with diazomethane, which is an explosion hazard and requires handling of highly carcinogenic precursors. We have developed a rugged high-performance liquid chromatographic (HPLC) method for analysis of the free-acid form of triclopyr in environmental water samples. This method features solid-phase extraction (SPE) and a lead diacetate cleanup to remove interfering humic substances. We have applied this method to the analysis of over two thousand water samples from a major environmental fate study we conducted on the Ouachita National Forest, Arkansas, but only 10 samples could be processed in one technician-day. Samples from environmental fate studies collected in one day frequently exceed 200-300 so there is a great need for a method which will accelerate the analysis of these samples.