Glyphosate and Metabolites

Registered for use in North America since 1974, glyphosate is a broad spectrum, non-selective systemic herbicide that controls weeds and other types of vegetation by inhibiting their ability to synthesize amino acids. It is generally considered to  have low toxicity to mammals, birds and aquatic species when used as directed but is currently the focus of renewed study, It has been regulated or has guidelines set for its concentration in drinking water in North America since the late 1980s to early 1990s.

Glyphosate is part of a group of herbicides referred to as phospho-herbicides. Aweak organic acid, the chemical formula for glyphosate is N-(phosphonomethyl)glycine. Glyphosate is the active ingredient in commercial herbicides such as Roundup, Expedite,Rodeo,Pondmaster, Silhouette. It undergoes rapid microbial degradation in plants, soil and water to the metabolite aminomethylphosphonic acid (AMPA).

Similar in structure to Glyphosate, Glufosinate (2-Amino-4-(hydroxy-methyl-phosphoryl)butanoic acid) is an herbicide that has been used in North America since the 1990s. It is the active ingredient in commercial herbicides such as Wipe Out, Liberty, Ignite, Rely, and Fianle. Glufosinate’s structure, properties, behaviour, and life time in the environment are similar to glyphosate. An increasing use of glufosinate is leading to scrutiny by some regulators.

 

Over the last three years AXYS has developed a LC-MS/MS based analytical method for analysis of glyphosate, AMPA, and glufosinate, in aquatic samples.  The compounds are analyzed as their 9-fluorenylmethylchloroformate (FMOC) derivatives and the method offers improved detection limits and specificity compared to traditional methods employing derivatization and fluorescence detection. It has been applied to the analysis of samples ranging from clean water to high organic content groundwater. Samples from both agricultural and urban areas are analyzed successfully with this method giving detection limits in the range of 30 to 50 ng/L.  

 

Glyphosate is non-selective herbicide directly applied to foliage and is commonly used in agriculture and forestry. In 2001, the EPA estimated that Glyphosate was the most commonly used active ingredient in pesticides with between 85 to 90 million pounds applied per year. The increased use of glyphoshate is linked to the introduction of glyphosate-resistant crops. Some formulations of glyphosate are also used in aquatic or wetland systems to control a variety of reeds and grasses.

 

Glyphosate can enter the environment through runoff or leaching from terrestrial application or through drift during aerial applications. Once in the environment, glyphosate has a relatively short residence time. It strongly adsorbs to soil particles and is eventually degraded by microbial action. The typical soil half life is about 50 days. It has little mobility in aquatic systems once adsorbed to soil or sediment particulate and is not expected to migrate into ground water. However, glyphosate applied in the aquatic environment, may have a slower breakdown in surface waters and levels of glyphosate may be increased. While it is not volatile when applied in the field, it may undergo some photodegradation in the environment. Some plants may not metabolize the glyphosate, and it can be translocated throughout the plant. The primary microbial metabolite of glyphosate AMPA, is also considered to be non-toxic and itself able to slowly degrade under further microbial action. The toxicity of glyphosate to mammals and birds tends to be low, however aquatic life and some soil invertebrates and organisms may be more sensitive. More significant environmental effects may result from loss of habitat or food sources for various species. The increasing use of glyphosate raises questions over its potential for residue accumulation in water and food.

 

Licensed in North America since the mid 1990s, glufosinate is a broad –spectrum herbicide and is used to control a wide range of weeds and other vegetation. Glufosinate is also used to dry crops before harvesting. It enters the environment through spray drift and runoff from treated sites. Glufosinate is mobile, but in most soils is not expected to leach into ground water. Glufosinate tends to not be acutely toxic to aquatic life, birds, and mammals when applied at the recommended rate, however there is a lack of information on chronic exposure. Human exposure may occur through ingestion of residue on food and daily intake limits have been established by WHO and other regulatory agencies. It is expected that the as genetically engineered glufosinate- resistant crops gain popularity, there will be an increase in the use of glufosinate in agricultural applications.

 

AXYS specializes in measurement of glyphosate to nanogram or lower concentrations from standard sample sizes. Our specialized sampling and analytical procedures may allow for much lower detection limits and reduced sample sizes in water matrices. We deliver legally defensible data under ISO 17025 certified systems applying  quality systems accredited by NELAP and CALA. Electronic Data Deliverables (EDD), customized for download to our clients’ relational databases, are available in addition to standard format report and full data packages. Please contact one of our Project Managers at 1 888 373 0881 or +1 250 655 5800 to discuss how AXYS can support your analytical advantage.

Please contact one of our Project Managers at 1 888 373 0881 or +1 (250) 655-5800 to discuss how AXYS can support your analytical advantage.