Determination of etidronic acid in vegetable-washing water by a simple and validated quantitative 31P nuclear magnetic resonance method

Abstract

Etidronic acid (1-hydroxyethylidene-1,1-diphosphonic acid, HEDP) is a common antioxidant additive used as detergent in the processing plants of agri-food industry for fruit and vegetable washing processes before commercialization. In the present work, and for the first time, a quick and reliable alternative to standard established methods for HEDP quantitation study has been performed in vegetable-washing processes applying 31P NMR. The proposed quantitative nuclear magnetic resonance method has been fully validated in water with different analysis times including a novel validation of the limits of detection and quantification depending on the target expected concentration, which results in considerable cost and time savings in those samples containing high concentrations of the compound. The limits of quantification (LOQs) ranged from 0.017% w/v for one minute of analysis (116 scans) to 0.003% w/v for 60 min of analysis (4745 scans). Additional validation parameters have been evaluated such as quantification procedure (comparing internal vs. external calibration), working range (from 0.01% to 0.05% w/v), recovery (95.0%–105.4%) and intra- and inter-day precision (from 0.9 to 4.3%) at 0.01 and 0.05% w/v. The developed method has successfully been applied for the determination of HEDP in 10 samples of agri-food processing industrial waters used for the cleaning of fruits and vegetables prior to their commercialization, providing adequate results and obtaining HEDP concentrations between 0.003 and 0.050% w/v.