Ion chromatographic determination of N-nitrosoglyphosate in a glyphosate matrix

doi:10.1016/S0003-2670(00)82757-9

Analytica Chimica Acta

Volume 230, 1990, Pages 29-34

https://doi.org/10.1016/S0003-2670(00)82757-9 Get rights and content

Abstract

The use of high-performance ion chromatography (HPIC) for the determination of N-nitrosoglyphosate [N-nitroso-N-(phosphonomethyl)glycine] is reported. NMR, spectrophotometric and electroanalytical measurements showed that two conformers of N-nitrosoglyphosate in slow equilibrium are always present. Separation of these conformers is achieved by using appropriate chromatographic conditions. The conductimetric detection of N-nitrosoglyphosate and glyphosate and application to the determination of traces of N-nitrosoglyphosate in complex matrices are also reported.

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Cited by (8)

Development of a sequential injection system with online photo-cleavage coupled to SPE for spectrophotometric determination of N-nitrosoglyphosate
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Citation Excerpt :
The product is quickly converted to nitrite, which reacts with Griess Method reagents N-(1-naphthyl)ethylenediamine (NED) and sulfanilamide (SAN), giving an azo red compound, that can be measured spectrophotometrically at 540 nm [11]. The literature presents few methods for NNG determination in GLY samples (technical grade and formulated products) [12,13] and all of them following the same approach mentioned above. Moreover, most of these methods are derived from the first procedure published in 1986 [9], and no major improvements or innovations have been seen over the years for determination of NNG.
The nitrosamine N-nitrosoglyphosate (NNG) is present as a minor impurity in technical-grade glyphosate (GLY), which is widely used in crops worldwide. Due to their high toxicity, regulatory agencies have established as 1.0 mg kg⁻¹ (w/w) the maximum concentration of NNG allowed in the technical standard of glyphosate to produce commercial formulations. Considering the high similarity between the structural formulas of NNG and GLY, a flow system with online photo-cleavage coupled to solid phase extraction is proposed. The NO group of NNG was cleaved by UV radiation (254 nm) and sequentially isolated in the form of NO₂⁻ at the strong anionic exchange sorbent in a mini-column. Griess reagent was used as eluent solution for the spectrophotometric determination of NO₂⁻, which was related to NNG concentration. The extraction procedure and photo-cleavage reaction were carried out in SIA system, resulting in a linear range from 0.05 to 1.25 mg kg⁻¹ NNG (R² = 0.9937) with sampling rate of 5.7 det h⁻¹. The pre-concentration factor was twelve-fold and good repeatability for the 0.05 mg kg⁻¹ solution of NNG was observed (r.s.d = 3.7%, n = 3) after 48 successive determinations, without significant changes in the analytical figures of merit. A limit of detection (LOD) of 3.1 × 10⁻³ mg kg⁻¹ was estimated and good recoveries (96.5%, n = 3) in the presence of high amount of glyphosate was obtained.
A simplified approach to the determination of N-nitroso glyphosate in technical glyphosate using HPLC with post-derivatization and colorimetric detection
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A simple and sensitive HPLC post-derivatization method with colorimetric detection has been developed for the determination of N-nitroso glyphosate in samples of technical glyphosate. Separation of the analyte was accomplished using an anionic exchange resin (2.50 mm × 4.00 mm i.d., 15 μm particle size, functional group: quaternary ammonium salt) with Na₂SO₄ 0.0075 M (pH 11.5) (flow rate: 1.0 mL min⁻¹) as mobile phase. After separation, the eluate was derivatized with a colorimetric reagent containing sulfanilamide 0.3% (w/v), [N-(1-naphtil)ethilendiamine] 0.03% (w/v) and HCl 4.5 M in a thermostatized bath at 95 °C. Detection was performed at 546 nm. All stages of the analytical procedure were optimized taking into account the concept of analytical minimalism: less operation times and costs; lower sample, reagents and energy consumption and minimal waste. The limit of detection (k = 3) calculated for 10 blank replicates was 0.04 mg L⁻¹ (0.8 mg kg⁻¹) in the solid sample which is lower than the maximum tolerable accepted by the Food and Agriculture Organization of the United Nations.
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Direct determination of n-nitrosoglyphosate in technical glyphosate using ion chromatography with UV detection
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Glyphosate: Properties, toxicity, use and legislation
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Ion chromatographic determination of N-nitrosoglyphosate in a glyphosate matrix

Abstract

J. Agric. Food Chem.

J. Agric. Food Chem.

Analyst