Pesticide residues analysis in honey using ethyl acetate extraction method: validation and pilot survey in real samples

Abstract

This paper presents a cost-effective and validated multi residue confirmatory method for the determination of 167 chemically different pesticides and a survey study on Cyprus honey samples. This method uses ethyl acetate for the extraction of pesticides from honey and the determination is performed with liquid chromatography (LC) coupled to mass spectrometry (MS) operating in tandem mode (MS/MS) and with GC–ECD (gas chromatography with electron capture detector) analysis. The LC-MS/MS analytical system is especially important in the analysis of polar and non-volatile pesticides. For the validation of the method, blank honey samples were spiked with 146 pesticides (organophosphorous, carbamates, triazoles, amides, neonicodinoids, strobilurines, phenylureas, bendimidazoles and others) for the LC-MS/MS analysis at three levels: 0.01, 0.05 and 0.1 mg kg⁻¹ and with 21 pesticides for the GC-ECD analysis at two levels: 0.01 and 0.05 mg kg⁻¹for organochlorines and 0.05 and 0.2 mg kg⁻¹for the pyrethroids. As blank sample, a sample of honey which did not contain detectable levels of the analytes sought was used. The validation study was in accordance to the DG SANCO guidelines. The scope of validation included recovery, linearity, limits of quantification and precision. Linearity is demonstrated all along the range of concentration that was investigated with correlation coefficients ≥0.98. Recoveries of the majority of compounds were in the 70%–120% range and were characterised by precision lower or equal to 20%. The validated method was used for a survey of 36 samples of honey produced in different areas of Cyprus and this is the first work on Cypriot honey samples investigating a broad range of pesticides. Only coumaphos was detected at concentrations higher than 0.01 mg kg⁻¹ in the 58.6% of the honey samples analysed for Coumaphos. The results were evaluated in accordance to the provisions of the Commission Regulation (EU) No 37/2010 on pharmacologically active substances and their classification regarding maximum residue limits (MRLs) in foodstuffs of animal origin. The concentrations of coumaphos in all positive samples were at levels much lower than the MRL.

Keywords:

• pesticides
• liquid chromatography
• tandem mass spectrometry
• gas chromatography
• electron capture detector
• honey
• ethyl acetate extraction

Acknowledgement

We thank the staff of the Pesticide Residues Laboratory of the State General Laboratory of Cyprus and in particular Mrs Elena Koupanou, Mrs Katerina Kouzapa and Mrs Elli Tsiaili.

ORCID

Despo Louca Christodoulou http://orcid.org/0000-0002-9659-1874