A simplified approach to the determination of N-nitroso Glyphosate in technical glyphosate using HPLC with post-derivatization and colorimetric detection

Abstract

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 um particle size, functional group: quaternary ammonium salt) with sodium sulphate 0.0075 mol/L (pH 11.5) (flow rate: 1.0 mL/min) 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 mol/L 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 (0.8 mg/kg) in the solid sample which is lower than the maximum tolerable accepted by the Food and Agriculture Organization of the United Nations.