Method validation for multiresidue pesticide determination in riverbed sediment using QuEChERS and GC-MS/MS and application in samples from an important watershed in Central Western Brazil

ABSTRACT

This study aims at validating a method used to determine pesticide residues in areas of cotton and soybean crops riverbed sediments in the São Lourenço River basin, an important watershed in Central Western Brazil, which has a history of pesticide use during cultivation. The optimised QuEChERS acetate methodology was validated, demonstrating good accuracy (71.7–116.4%), except for carbosulfan (51.0%), and good precision (intra-day repeatability 5.1–20.0% and inter-day reproducibility 6.2–18.5%) except for trifluralin and carbosulfan. The linearity was satisfactory with coefficient determination R² > 0,99. The use of internal standard, triphenyl phosphate (TPP), showed better results during validation than without its use. The limits of detection and quantification range were 1.07 to 10.7 ng g⁻¹ and 5.0 to 15.0 ng g⁻¹ of dry weight sediment, respectively. The matrix effect was evaluated and a strong signal enhancement was observed using gas chromatograph (GC) coupled with spectrometry mass (MS/MS). The use of matrix-matched standards was compensated by better sensibility in the analysis. The use of simple, fast, sensitive methodology combined with the use of two transitions, retention time and ion ratio, makes it suitable for the analysis of complex samples such as sediment. Finally, the method was applied to samples of river sediment collected near cotton and soybean cultivation. Twelve sediment samples from the São Lourenço River basin, Mato Grosso, were analysed to test the applicability of the validated method. Among the 22 analysed pesticides, cyhalothrin (ʎ and δ) was detected in two samples (59.8 and 66.9 ng g⁻¹), difenoconazole in five samples (<LOQ to 34.4 ng g⁻¹), azoxystrobin in one sample (9.5 ng g⁻¹) and bifenthrin was detected in 10 samples whose levels ranged from < LOQ to 151.4 ng g⁻¹.

KEYWORDS:

• Sediment
• pesticide
• validation
• QuEChERS
• internal standard
• GC-MS/MS

Acknowledgments

The author acknowledges EMBRAPA and UFMT.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study received financial support from Embrapa (SEG 1317000790003).