# Development and Validation of a QuEChERS-Based LC–MS/MS Method for Natamycin in Imported Agricultural Commodities in Korea

## TL;DR

This paper develops a sensitive method to detect natamycin in agricultural products in Korea, ensuring compliance with strict residue limits.

## Contribution

A novel QuEChERS-based LC–MS/MS method for detecting natamycin in five agricultural commodities under Korean regulations is developed and validated.

## Key findings

- The method achieved mean recoveries of 82.2–115.4% and %CV values of 1.1–4.6% across five matrices.
- Natamycin was detected at 6.8 min with no interfering peaks in all tested matrices.
- Matrix effects were classified as 'soft' or 'medium', validating the method for regulatory use under Korea's PLS.

## Abstract

Natamycin is widely used in other countries for the postharvest treatment of agricultural commodities to prevent fungal growth. However, since no MRL has been set in Korea, natamycin residues are regulated under the Positive List System (PLS) with a uniform limit of 0.01 mg/kg, requiring the development of highly sensitive and reliable analytical methods. In this study, a QuEChERS-based analytical method was developed and validated for the quantification of natamycin in five agricultural commodities—soybean, mandarin, hulled rice, green pepper, and potato—using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Extraction using methanol with 3 g of MgSO4 resulted in high recoveries without crystallization, and clean-up with MgSO4 and C18 effectively reduced matrix interferences blow <50%. Natamycin was detected in all five matrices at 6.8 min without any interfering peaks. The MLOQ was determined at 0.01 mg/kg for all five matrices. The mean recoveries (82.2–115.4%) and %CV values (1.1–4.6%) values were within the acceptance criteria defined by the CODEX guidelines. Matrix effects were classified as “soft” for mandarin (|ME| < 20%) and “medium” for soybean, hulled rice, green pepper, and potato (20% ≤ |ME| < 50%). The analytical method for natamycin was validated as suitable for regulatory safety monitoring under the Korean PLS.