Analysis of pesticide residues in strawberries and soils by GC-MS/MS, LC-MS/MS and two-dimensional GC-time-of-flight MS comparing organic and integrated pest management farming

Abstract

This study analysed 22 strawberry and soil samples after their collection over the course of 2 years to compare the residue profiles from organic farming with integrated pest management practices in Portugal. For sample preparation, we used the citrate-buffered version of the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. We applied three different methods for analysis: (1) 27 pesticides were targeted using LC-MS/MS; (2) 143 were targeted using low pressure GC-tandem mass spectrometry (LP-GC-MS/MS); and (3) more than 600 pesticides were screened in a targeted and untargeted approach using comprehensive, two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOF-MS). Comparison was made of the analyses using the different methods for the shared samples. The results were similar, thereby providing satisfactory confirmation of both similarly positive and negative findings. No pesticides were found in the organic-farmed samples. In samples from integrated pest management practices, nine pesticides were determined and confirmed to be present, ranging from 2 µg kg⁻¹ for fluazifop-p-butyl to 50 µg kg⁻¹ for fenpropathrin. Concentrations of residues in strawberries were less than European maximum residue limits.

Graphical Abstract

Keywords:

• pesticide residue confirmatory analysis
• chromatography
• mass spectrometry
• QuEChERS
• strawberry
• soil
• farming practices

Funding

This research was supported by a PhD grant [grant number BD/47200/2008] from the Fundação para a Ciência e a Tecnologia, co-financed by POPH/FSE (Programa Operacional Potencial Humano/Fundo Social Europeu); and by grant number PEst-C/EQB/LA0006/2011.