Liquid Chromatographic Method for Quantitation of Glyphosate and Metabolite Residues in Organic and Mineral Soils, Stream Sediments, and Hardwood Foliage

Abstract

A liquid chromatographic method for determining glyphosate (GLYPH) and its major metabolite aminomethylphosphonic acid (AMPA) in various environmental substrates is described. Ion-exchange column chromatography is coupled with post-column ninhydrin derivatization and absorbance detection at 570 nm. Use of a valve-switching technique allowed quantitation of both analytes in a single chromatographic run and eliminated slow-eluting, coextracted interferences. The method was successfully used to quantitate GLYPH and AMPA in organic and mineral soils, stream sediments, and foliage of 2 hardwood brush species. Mean recovery efficiencies for GLYPH as determined from fortified blank field samples were as follows: bottom sediment 84%, suspended sediment 66%, organic soils 79%, mineral soils 73%, alder leaf litter 81%, salmonberry leaf litter 84%, and artificial deposit collectors 87%. Precision for GLYPH determination was good with less than 14% coefficient of variation on mean recovery for all substrates. Limits of detection were lowest for sediments (0.01 μg/g dry mass) and highest for foliage substrates (0.10 μg/g dry mass). Using this system, 6 samples/person/day were routinely analyzed.

Phosphate addition enhances alkaline extraction of glyphosate from highly sorptive soils and aquatic sediments

“…In line with Marek and Koskinen, 45 we found higher recoveries for AMPA than for glyphosate in soils, which is in contrast to many other works, 39,46,47 and points to specific sorption characteristics present in our samples. 22 Sample properties important for glyphosate and AMPA extraction are still not fully understood (see e.g.…”

“…Refs. 13, 47), which is augmented by the fact that relevant soil characteristics such as those given in Table 1 are seldom reported (especially, knowledge on mineral composition would be of high interest). Three major aspects influence the ad‐ and desorption of glyphosate and AMPA: (i) At very high pH, desorption is supported by coulomb repulsion between negatively charged analytes and soil mineral surfaces 48 .…”

“…Refs. 13,47), which is augmented by the fact that relevant soil characteristics such as those given in Table 1 are seldom reported (especially, knowledge on mineral composition would be of high interest). Three major aspects influence the ad-and desorption of 8) † relative standard deviation RSD in percent in parenthesis (triplicate extraction, duplicate CE-MS measurement, thus n = 6) (see Section 2.5): A: drained area; SSO: Strahler stream order.…”

“…35,39,47 Common purification strategies after extraction included flocculation with CaCl 2 , 63 liquid-liquid extraction with organic solvents, 32,46 additional acidificationneutralization steps, 12,37 or solid phase extraction, the last can also be used to remove multivalent metal cations. 38,39,47 Strongly alkaline extraction conditions, e.g. with 600 mmol L −1 KOH, required an additional neutralization step prior to FMOC-derivatization at pH 9.…”

Application of ZnO Nanocrystals as a Surface-Enhancer FTIR for Glyphosate Detection

“…Glyphosate’s capacity to adsorb strongly onto clay minerals [ 11 ] and organic or mineral particles in water [ 12 , 13 ] and its high affinity with metal cations impose great difficulties on its detection without pretreatment methods [ 14 ]. The behavior of glyphosate has been examined by several research groups, showing the tendency of transitions in some trivalent metal ions and divalent alkaline-earth metal ions to form 1:1 (e.g., Ca(II) and Cu(II) [ 15 , 16 ]) and 2:1 metal chelates with glyphosate in solution [ 17 ].…”