Time-integrated sampling of glyphosate in natural waters

• Published in: Chemosphere (Oxford) Vol. 90; no. 6; pp. 1821 - 1828
• Main Author: Kylin, H.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.02.2013; Elsevier
• Subjects: acidification; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid - analysis; Aminomethylphosphonic acid; AMPA; Applied sciences; bottles; colloids; Continental surface waters; Environmental monitoring; Environmental Monitoring - methods; Environmental Sciences; Exact sciences and technology; Fresh Water - chemistry; Glycine - analogs & derivatives; Glycine - analysis; Glyphosate; Herbicides - analysis; hydrochloric acid; hydrophobicity; metals; Miljövetenskap; N-(phosphonomethyl)glycine; Natural water pollution; pesticide residues; Pollution; Sample integrity; Sample preservation; surface water; Water Pollutants, Chemical - analysis; Water treatment and pollution; N-(phosphonomethyl)glycine; Aminomethylphosphonic acid; Sample preservation; AMPA; Environmental monitoring; Sample integrity; Pesticides; Acidification; Organic phosphonate; Systemic; Glyphosate; Herbicide; Phosphorus Organic compounds; Environment impact; Surface water; Sample conservation; Water pollution; Sampling; sample integrity; Glyfosat; environmental monitoring; miljöövervakning
• ISSN: 0045-6535; 1879-1298; 1879-1298
• DOI: 10.1016/j.chemosphere.2012.09.020

Glyphosate loss from natural waters. [Display omitted] ► Glyphosate losses are likely in monitoring programs using time-integrated sampling. ► Losses are partly due to degradation, partly to binding to metals or humus. ► Refrigerated time-integrating samplers reduces degradation and increases recovery. ► Acidification during sampling increases recovery by reversing metal and humus binding. ► Labelled surrogate standards are imperative to identify false negatives. Environmental monitoring of pesticide residues in surface water is often done with time-integrated sampling where a specified volume is sampled each hour during, e.g., a week, thus avoiding at momentary high or low extreme concentrations. However, sampling over an extended period of time can result in losses of easily degradable analytes, why the stability of the target analytes over the timespan of the sampling must be checked. Glyphosate is one of the most widely used herbicides. Because of its chemical complexity, glyphosate binds differently to metals and colloids at different pH, and the degradation may also be affected. Recovery of glyphosate from spiked natural waters after 1 and 3weeks of storage was higher when the samples were acidified to approximately pH 2 rather than at their natural pH. Keeping the samples refrigerated to 4°C in darkness also enhanced recovery, while glyphosate losses were substantial from samples kept at their natural pH at 20°C. Total loss of glyphosate was observed in some samples kept at natural pH, 20°C, and daylight; a loss partly due to binding to metals or colloids that could only partially be reversed by acidification. For 1-week time-integrated sampling a small amount of hydrochloric acid in a piece of heat-sealed hydrophobic micro-porous tubing is added to the sampling bottles before deployment, a procedure that acidifies the samples during collection keeping them below pH 2 until analysis, thus minimising losses of glyphosate. The method also allows determination of the primary degradation product aminomethylphosphonic acid (AMPA).