Development and validation of analytical methods for multi-residue determination of pesticides in lettuce by liquid chromatography coupled to tandem mass spectrometry

Author(s)

Fernanda Ribeiro Begnini Konatu

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2014-08-19

Examining board members

Isabel Cristina Sales Fontes Jardim; Ednei Gilberto Primel; Martha Bohrer Adaime; Fabio Augusto; Carla Beatriz Grespan Bottoli

• Advisor: Isabel Cristina Sales Fontes Jardim

Abstract

According to the Brazilian Health Surveillance Agency, in recent years, lettuce has shown irregularities in Brazil, due to the presence of pesticides at levels above the permissible maximum residue level. Therefore, the development of a multi-residue method for determination of pesticides in lettuce becomes necessary. For this, the separation, confirmation and quantification of 16 pesticides in lettuce was realized using high- and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry with a triple quadrupole mass analyzer, operating in a multiple reaction monitoring mode with positive electrospray ionization. The pesticide extraction was performed using an optimized QuEChERS method, employing acetonitrile as extraction solvent, citrate buffer as partitioning salt, vortex agitation, centrifugation at 5000 rpm for 5 minutes and clean-up with PSA, MgSO4 and graphitized carbon black. The methods developed were validated according to Document SANCO No 12571/2013, and proved to be selective, accurate and precise, presenting recoveries from 70 to 120% and a relative standard deviation = 20% for all pesticides. Linearity was evaluated at 5 levels of fortification, employing matrix-matched standard solutions, providing coefficients of determination higher than 0.990, residuals = 20% and limits of quantification from 3 µg/kg. The methods were applied to several varieties of lettuce (green-leaf, looseleaf, iceberg, green-bowl and red-leaf) and to spinach (vegetable of similar composition), showing good results. Samples of several varieties of lettuce were purchased from commercial markets in Campinas, SP, and pesticides were detected in 43% of the samples at concentrations above the levels authorized by ANVISA, indicating the need to continue to monitor lettuce (AU)

• FAPESP's process: 11/23127-0 - Development and validation of analytical methods for the determination of multiresidues of pesticides in lettuce, using ultra-performance liquid chromatography and liquid chromatography coupled with tandem mass spectrometry.
• Grantee: Fernanda Ribeiro Begnini
• Support Opportunities: Scholarships in Brazil - Doctorate