Elsevier

Food Chemistry

Volume 281, 30 May 2019, Pages 85-90
Food Chemistry

Analytical Methods
Development of precise GC-EI-MS method to determine the residual fipronil and its metabolites in chicken egg

https://doi.org/10.1016/j.foodchem.2018.12.041Get rights and content

Highlights

  • First GC-EI-MS method to determinate fipronil and its metabolites in chicken egg.

  • Signal intensity of analyte and TIC of sample were evaluated simultaneously.

  • Oxidation was the main metabolism pathway of fipronil in chicken egg.

Abstract

Fipronil is a highly toxic insecticide, and fipronil egg scandal greatly threaten people’s health. Herein, a precise and reliable method was developed for the determination of fipronil and three metabolites in chicken egg by GC-EI-MS. Sample pretreatment took about 20 min and baseline separation of four analytes were realized within 12 min by GC–MS. Moreover, the limits of detection were 0.2–0.5 ng g−1 and the limits of quantitation was 0.5–1 ng g−1 with relative standard deviations (RSDs) lower that 3.32%. Satisfactory recoveries were get in the range of 81.16–103.57% for three levels of spiked samples. Finally, the developed method has been applied for the analysis of egg samples from four sources. Results showed that fipronil and fipronil-sulfone were detected in three samples, while fipronil-desulfinyl and fipronil-sulfide were totally absent. The method showed great promising in quantification of fipronil and its metabolites in food safety affairs.

Introduction

Fipronil is a broad-spectrum insecticide attributed to the phenylpyrazole family. Due to its high toxicity to invertebrates and long persistence, it had been one of the most widely used insecticide to control household and agricultural pests from its appearance in market. Fipronil is a neurotoxic compound which could prevent the inhibition of invertebrate gamma-aminobutyric acid gated chloride channels in the central nervous system (Ozoe et al. (2015)). Ascribed to its neurotoxins, it could deprive benthic macroinvertebrate’s motor ability (Weston & Lydy, 2014). Moreover, fipronil also showed genotoxicity and cytotoxicity to many vertebrate animals, like mammals, birds, fish, reptiles and so on (Gibbons, Morrissey, & Mineau, 2015). Fipronil was reported to degrade to three main products and some of the metabolites were more toxic than itself: photolysis to fipronil-desulfinyl, reduction to fipronil-sulfide and oxidation to fipronil-sulfone (Kaur, Mandal, Kumar, & Singh, 2015). Others reported that fipronil-sulfone and fipronil-desulfinyl were more active at the mammalian chloride channel than that in insect (Peng, Li, Xia, Peng, & Feng, 2016). At the same time, fipronil could have negative effects on the liver, kidneys and thyroid glands of human. The estimate of acute reference dose by WHO and Food and Agriculture Organization was 0.003 mg/kg bw.

Considering its serious toxicity, the use of fipronil has been totally banned in some countries, while it is still used in restricted field like seed coated formulation in other countries. To ensure human’s health and evaluate the residual level, a number of studies were conducted to determine fipronil distribution in various food matrix, like apple and cucumber (Portolés, Mol, Sancho, López, & Hernández, 2014), honey (García-Chao et al., 2010), cabbage (Bhardwaj et al., 2012), maize (Wang, Hu, & Liu, 2014), edible oils (Peng et al., 2016), sugarcane (Ramasubramanian & Paramasivam, 2017), meat (Sartarelli, De MacEdo, De Sousa, Nogueira, & Brondi, 2012), fish liver (Caldas et al., 2013), peanut (Li, Li, Wang, Feng, & Han, 2015), okra (Hingmire, Oulkar, Utture, Ahammed Shabeer, & Banerjee, 2015), chrysanthemum (Chen et al., 2018) and so forth. Due to the wide contamination in food matrix and large daily intake of various food, fipronil has high probability of posting great threat to human’s health and human exposure needed greater concern. Recently, fipronil egg scandal occurred in European Union involved more than 15 states and astonished the world (“Fipronil egg scandal: What we know,“ 2017). The detected concentration of fipronil was many times higher than the European maximum residue limit in bird egg (5 ng g−1). Besides European countries, fipronil contaminated eggs were also found in Asian areas like China's Hong Kong and South Korea. Effective control of fipronil contaminated eggs strongly depends on reliable analytical methods. A precise and reliable method for the determination of fipronil and its metabolites in chicken egg was of highly demand for the quality control in food safety and has a significance towards human’s health. Gas chromatography tandem mass spectrometry (GC–MS) which was frequently used for the separation and quantification of volatile organic analytes (Shen et al., 2018) with thermal stability is also very fit for fipronil analysis. Moreover, GC–MS method showed advantages in standard MS database, no organic solvent consumption, high sensitivity, low cost and fit for routine analysis. Especially, GC-MS/MS could removes matrix interferences and provides reliable confirmation. Whereas, there was only one report about fipronil detection method in chicken egg that is based on GC-NCI-MS (Shen et al., 2017). However, fipronil and fipronil-sulfide were not baseline separated and relative standard deviation (RSD) of recovery was very high, which was adverse to guarantee the required accuracy of final results. Efficient sample preparation before GC–MS analysis becomes a prerequisite to ensure highly accurate results.

In this work, we developed a reliable and robust sample preparation methods based on GC–MS for the extraction of fipronil and its metabolites residues in chicken egg samples. After protein precipitation, liquid-phase extraction, liquid–liquid re-extraction and solid-phase extraction (SPE), the extract was analyzed by GC–MS with multiple reaction monitoring (MRM) mode. To the best of our knowledge, this is the first report about determination of fipronil and its metabolites in chicken egg by GC-EI-MS which showed great promising in quantification of fipronil and its metabolites in food safety affairs.

Section snippets

Material and methods

Fipronil, fipronil-desulfinyl, fipronil-sulfide and fipronil-sulfone standards were purchased from Alta Scientific (Tianjin, China). HPLC grade n-hexane, isooctane and acetonitrile were supplied by Merck (Darmstadt, Germany) and Fisher Scientific (New Jersey, USA). Ultrapure water was obtained from a Milli-Q plus apparatus (Milford, USA). Sodium chloride was bought from Sinopharm Chemical Regent Co. Ltd. (Beijing, China). For sample preparation, Acrodisc GHP syringe filter (0.2 μm pore size)

Optimization of the pretreatment procedure

For clearance of optimization, the normalized peak areas are shown in the following results.

Conclusions

In this work, the GC-EI-MS methodology of detecting fipronil and its metabolites residues in chicken egg samples was developed by combining with protein precipitation, liquid-phase extraction, liquid–liquid re-extraction and solid-phase purification. In detail, 5 g chicken egg sample was extracted by 20 mL acetonitrile under sonication for 5 min under 20 °C. Then, 1 g sodium chloride was added and votex-mixed for 1 min. After centrifugation, 20 mL hexane was added for re-extraction. Votex and

Acknowledgements

This work was supported by the National Key R&D Program of China (2016YFF0201106 and 2016YFE0206500) and National Natural Science Foundation of China (Grant No. 21804123).

Conflict of interest

The authors declared no conflict of interest.

References (26)

  • M. Zhang et al.

    Determination of residual fipronil in chicken egg and muscle by LC-MS/MS

    Journal of Chromatography B

    (2016)
  • S.S. Caldas et al.

    A vortex-assisted MSPD method for the extraction of pesticide residues from fish liver and crab hepatopancreas with determination by GC-MS

    Talanta

    (2013)
  • BBC news. Fipronil egg scandal: What we know, 2017, URL http://www.bbc.com/news/world-europe-40878381. Accessed 18...
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