TITLE:
Improved Analytical Methods for Determination of Residues of Nitrapyrin and 6-Chloropicolinic Acid in Different Crop Matrices by Liquid Chromatography-Tandem Mass Spectrometry
AUTHORS:
Fabiola G. Zuno-Floriano, Riza L. Reyes-Punongbayan, Matt J. Hengel
KEYWORDS:
Herbicide, Agricultural Products, External Calibration, LC-MS/MS, Registration
JOURNAL NAME:
Journal of Agricultural Chemistry and Environment,
Vol.13 No.3,
July
12,
2024
ABSTRACT: Novel analytical methods were developed for the determination of nitrapyrin and 6-chloropicolinic acid (6-CPA) residues in agricultural products. Nitrapyrin was extracted with hexane: toluene (1:1, v/v) and 6-CPA with 0.1 N sodium hydroxide (NaOH). For nitrapyrin, samples were cleaned with silica solid phase extraction (SPE) and for 6-CPA with C18 or carbon SPE. Analysis was performed by liquid chromatography-tandem mass spectroscopy (LC-MS/MS) with external calibration (0.010 to 0.0010 µg∙mL−1 for nitrapyrin and 0.0050 to 0.00025 µg∙mL−1 for 6-CPA). Recoveries for nitrapyrin and 6-CPA were 68% - 102% and 66% - 90%, respectively. Nitrapyrin was detected in celery and onion (−1) and 6-CPA in onion, mustard greens and lettuce (−1). Lower level method validation (LLMV) for nitrapyrin and 6-CPA was 0.020 µg∙g−1 and 0.050 µg∙g−1, respectively. The methods presented in this study are robust and were utilized for the registration of nitrapyrin on agricultural commodities in the United States.