The broad spectrum, non-selective herbicides glyphosate (Roundup®) and glufosinate (Liberty®) are used globally for the control of grass and broadleaf weeds in agricultural and residential settings. Glyphosate usage has increased in agriculture over the last 20 years with the development of glyphosate-resistant corn and soybeans (Roundup Ready). The widespread use of glyphosate has led to weed resistance. In response, new varieties of glufosinate resistant crops have been developed, leading to an increase in glufosinate usage as a weed control tool. Both herbicides are relatively non-toxic to mammals, birds, fish and invertebrates, and both break down rapidly in the environment. Despite these desirable characteristics, both herbicides may be present at low concentrations in crops, soil, water, feed and food. In the United States, residue tolerance levels for the parent active ingredients glyphosate and glufosinate, and their metabolic breakdown products in crops range from 0.1 to 300 parts per million (ppm). However, state-specific and international tolerance levels can be much lower (0.01 ppm).
Laboratory analysis to determine glyphosate and glufosinate levels in environmental and feed/food samples has been challenging. Both active ingredients are highly polar, water-soluble chemicals that don’t lend themselves to traditional gas or liquid chromatographic techniques without tedious derivatization reaction procedures. EPL Bio Analytical Services (EPL) has recently developed and validated a method which is simple, rapid and sensitive for the determination of glyphosate and glufosinate and the metabolic breakdown products of both. The method involves no derivatization and utilizes high-speed liquid chromatography with tandem mass spectrometry detection. The mass spectrometer detector (AB Sciex 6500) is state-of-the-art and is the most sensitive instrument of its kind on the market. EPL employs two 6500 systems and has recently purchased the next generation of this instrument, the 6500 Plus. Herbicide levels as low as 0.01 ppm are accurately measured using the new methodology.
The following chemical compounds are determined:
- Aminomethylphosphonic Acid (glyphosate metabolite)
- Glufosinate Propionic Acid (glufosinate metabolite)
- N-acetyl Glufosinate (glufosinate metabolite-only found in crops expressing glufosinate resistance)