Analysis of N-Nitroso Glyphosate in Glyphosate Samples

Glyphosate (GP) is a non-selective, postemergence herbicide widely used for weed and vegetative control. Glyphosate itself readily forms an N-nitroso derivative. Among the impurities of commercial glyphosate, N-nitrosoglyphosate (NNG) is of great concern due to its toxicity. However the accepted methodology for NNG determination – proposed by Monsanto Agricultural Company in 1986 (1) is difficult to implement due to complicated instrumentation and operating conditions and relatively low sensitivity.

Figure 1

This application note presents a simple and sensitive method combining an effective separation of Nitrosoglyphosate from Glyphosate on anion exchange column with an improved single-step derivatization of NNG (2). Pickering Laboratories Vector PCX is uniquely suited to handle highly corrosive reagents and is factory configured for Nitrosoglyphosate analysis. This advance in instrumentation and methodology provides a rugged method that easily meets the new limit of 1 ppm NNG in Glyphosate formulations as set by Food and Agricultural Organization of the United Nations (FAO) (3).

Figure 2

Notes

Since the reagent is highly corrosive, the post column derivatization system must be flushed with water methanol (80:20) after running the samples.

References

(1) Monsanto Agricultural Products Company, Standard Analytical Method No. AQC-684-86,1986.

(2) Manuela Kim, Jorge Stripeikis, Fernando Inon, Mabel Tudino, Talanta 72 (2007) 1054–1058.

(3) FAO Specifications and Evaluations for Plant Protection Products: Glyphosate, N- (phosphonomethyl)glycine, evaluation Report 284/2001.

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