Determination of free and hydrolyzable residues of 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol in potatoes

Abstract

Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Deparment of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.2,4-D and 2,4-DCP at low ppb (nanograms per gram) levels

Comparison of free and total residues of (2,4-dichlorophenoxy)acetic acid and 2,4-dichlorophenol in millet resulting from postemergence and preharvest treatment

“…Chow et al (1971), and Lokke (1975). Earlier tests of potatoes (Bristol et al, 1982) showed that acid hydrolysis was as efficient as alkaline hydrolysis in releasing bound residues of 2,4-D. Triplicate samples of 2,4-D-treated millet seed subjected to a 2-h acid hydrolysis contained 0.16 ± 0.007 ppm of 2,4-D. Three identical samples subjected to a 2-h acid hydrolysis followed by a 2-h reflux in alkali showed residues of 0.13 ± 0.002 ppm of 2,4-D. Since no additional 2,4-D was released by the alkaline hydrolysis, acid hydrolysis was used for the analysis of the millet samples.…”

“…Earlier studies (Chow et al, 1971;Crosby, 1964; Yip and Ney, 1966) indicated that significant amounts of phenoxyalkanoic acids occurring in plants are conjugated and may be converted to the free form by acid or alkaline hydrolysis. Conjugated residues of 2,4-D comprised 10-25% of the 2,4-D recovered from potato tubers (Bristol et al, 1982). Lokke (1975) found that 88-92% of the 2,4-D recovered from barley grain occurred as conjugated residues.…”

“…Analytical Procedure. Details for both the FRA and HRA procedures for trace residues of 2,4-D and 2,4-DCP in potatoes have been published (Bristol et al, 1982). Some modifications were made to accommodate differences in sample matrix encountered with the millet samples.…”

“…For determination of the recovery of 2,4-D through each step of the FRA procedure, 1-mL aliquots of an aqueous solution containing 6.79 jtg/mL [acetic-2-uC]-2,4-D (about 271000 dpm/mL) were added to 25.0-g samples of millet seed and forage. Duplicate 1.00-mL samples were taken at each step of the procedure, and radioassays were performed by using the procedure of Bristol et al (1982).…”

Comparison of extraction/hydrolysis procedures for the determination of acidic herbicides in plants: residues of mecoprop in barley following postemergence application

“…With acid and base hydrolysis, two strategies have been employed by analysts when incorporating the hydrolytic step. In one approach, the plant tissue is subjected to extended hydrolysis followed by partitioning of the "free" acidic herbicide into an organic phase (Bjerke et al, 1967;Cessna, 1980;Bristol et al, 1982;Frank et al, 1983; Galoux et al, 1983;Smith, 1984;Smith et al, 1986;Steinwandter, 1989). The other approach involves extracting the free acidic herbicide plus any conjugates directly into an organic phase and then effecting hydrolysis (Hamilton et al, 1971; Buckland et al, 1973;Feung et al, 1973;Beynon et al, 1974;Shimabukuro et al, 1979;Eronen et al, 1979;Scheel and Sandermann, 1981).…”