Ochratoxin A in Chinese dried jujube: method development and survey

Abstract

A method was developed for the determination of the mycotoxin ochratoxin A in dried jujube (Zizyphus jujuba Miller) using alkaline methanolic extraction, immunoaffinity column clean-up (IAC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination. The limit of detection (LOD) was 0.01 μg kg^–1 and limit of quantification (LOQ) was 0.03 μg kg^–1. The average recoveries were 82%, 98% and 115% at 5, 0.5 and 0.1 μg kg^–1 spiked levels with relative standard deviations (RSD) of 2.9%, 5.2% and 9.2% accordingly. The method showed good linearity for both solvent standard calibration and matrix-matched standard calibration with correlation coefficients of 0.9998 and 0.9997 respectively. The intra-day precision RSD was 3.3% and the inter-day precision RSD was 4.0%. In addition, there was almost no matrix interference in LC-MS/MS detection after the IAC clean-up process. The proposed analytical set-up was successfully used to test 20 samples that were collected from local markets and stores. The results showed that all the samples were positive and the amount of OTA ranged from < 0.01 to 0.18 μg kg^–1, with a mean level of 0.14 μg kg^–1. In spite of the high positive rate, samples with this level would not cause significant health effects after consumption.

Keywords:

• ochratoxin A
• Chinese dried jujube
• immunoaffinity clean-up
• liquid chromatography-tandem mass spectrometry

Acknowledgement

We gratefully thank Jingming Li for supplying the dried jujube samples.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 31471656].