Date: March 2016
Determining glyphosate, AMPA and glufosinate in foodstuffs using online SPE-LC-MS/MS after FMOC derivatisation
Glyphosate is a pesticide with systemic effects, and is used as a main component in lots of broad-range herbicides. Since 1974, glyphosat has been used in agriculture as the Roundup™ preparation. As well as other properties, it is also used in this sector to accelerate the ripening of grains. Aminomethylphosphonic acid (AMPA) is the main breakdown product of glyphosate in plants.
Glufosinate is a non-selective contact herbicide with partially systemic effects. Glufosinate is a glutamine synthetase inhibitor, which leads to the accumulation of ammonium ions and inhibition of photosynthesis. Due to its structural similarities, glufosinate is quantified simultaneously with glyphosate and AMPA in a one analysis method.
The methodological framework for the determination of glyphosate, AMPA and glufosinate in foodstuffs is the QuPPE method. The following derivatisation is as set out in AB SCIEX Schreiber et al., Automated Derivatisation, SPE Cleanup and LC-MS/MS Determination of Glyphosate and Other Polar Pesticides (2013). The existing method was optimised by the Institut Kirchhoff Berlin GmbH, in order to be able to better quantify glyphosate, glufosinate and AMPA even in complex matrices such as grains, pulses and herbs, and from a content of 0.01 mg/kg. This method can similiarly be used for liquid matrices such as water and beer.
Glyphosate, AMPA and glufosinate are extracted from the homogenised sample using a water/methanol mixture, and then derivatised with FMOC. The extract is measured using online SPE-LC-MS/MS. Quantification is by the method in our internal standards.
The toxicological classification of glyphosate is currently subject to much discussion. In March 2015, on the basis of the studies it had at its disposal, the World Health Organization (WHO) classified glyphosate in carcinogen group 2A as probably carcinogenic to humans. However, after examining all available studies, the BfR and the EFSA came to the conclusion that, on the basis of current scientific knowledge, and provided glyphosate is used as intended, it poses no carcinogenic risk to humans. According to the view of the BfR, AMPA is not more toxic than glyphosate. Glufosinate is toxic for reproduction, and according to the German Federal Department of Agriculture (BMELV), the EU is discussing banning it across Europe in 2017.
In accordance with Directive (EC) 396/2005, maximum quantities for glyphosate and glufosinate are listed in substance/culture combinations, depending on the application type, in the EU Commission’s pesticides database. As set out in article 18, paragraph 1, letter b of Directive (EC) 396/2005, products for which no maximum residue content has been set must not exceed a content of 0.01 mg/kg. Whether it remains a permitted pesticide will be decided by the EU Commission by June 2016.
From March 2014 to March 2016, the Institut Kirchhoff Berlin GmbH analysed more than 200 samples of food for glyphosate. In around 15% of these samples, glyphosate content from 0.01 mg/kg up to 26 mg/kg was quantified.