Synthesis and evaluation of selective sorbents MIP and RAMIP for the analysis of fluoroquinolones in environmental complex matrix by column-switching LC-MS/MS

Author(s)

Scarlet Nere Ortega

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT)
• Defense date: 2017-05-12

Examining board members

Álvaro José dos Santos Neto; Paulo Clairmont Feitosa de Lima Gomes

• Advisor: Álvaro José dos Santos Neto

Abstract

The increased use of antibiotics has led to a higher presence of these molecules into environment. Therefore, there is a raising concern on this matter, since antibiotics may yield microorganisms resistant to their effects. Aiming to monitoring the presence, persistence and destination of these drugs on the environment, there is an urge for the development of highly sensitive analytical methods, capable of detecting at the μg L-1 to the ng L-1 concentration levels. In this fashion, this thesis focuses on the synthesis of selective sorbents such as molecular imprinted polymers (MIP) and restricted access molecular imprinted polymers (RAMIP) for the analysis of complex water samples containing fluoroquinolones. Additionally, it includes the use of these sorbents by online solid phase extraction (SPE) coupled to LC-MS/MS, using a column-switching (CS) setup. Two MIPs (MIP1 and MIP2) were synthesized using ofloxacin as template, methacrylic acid as monomer and ethylene glycol dimethacrylate (MIP1) or trimethylpropane trimethacrylate (MIP2) as cross-linking agent. The glycerol dimethacrylate and hydroximethyl dimethacrylate were employed to promote the formation of a hydrophilic surface layer on MIP1 and MIP2 (RAMIP1 and RAMIP2). The synthesized polymers (MIP1, MIP2, RAMIP1, RAMIP2) were packed into 21,7 x 2,0 mm columns and used for the direct analysis of complex water matrices using an online CS-LC-MS/MS system, for the evaluation of the selectivity, macromolecules exclusion and relative process efficiency. The synthesized phases were coated with humic acids (MIP1-AH, MIP2-AH, RAMIP1-AH, RAMIP2-AH) and were compared to the extraction phase HLB-AH regarding its selectivity and capability of proteins and humic acid exclusion. The synthesized polymers displayed selectivity for the analysis of fluoroquionolones when compared to the possible interferents, specially the MIP1 and MIP1-AH, with a higher selectivity when compared with the commercial phases Oasis® HLB and Strata X®. Additionally, when percolating an aqueous solution containing 44 mg mL-1 of bovine seric albumin (BSA) it was possible to eliminate ca. 92-100% of the proteins and 94-96% of exclusion was obtained when percolating an aqueous solution containing 6 mg mL-1 of humic acid. The relative process efficiency of sample preparation resulted from the synthesized polymers was comparable to that of the commercial phase, however the relative standard deviation (RSD) for the HLB phase was higher. The polymer MIP1-AH displayed better efficiency for the extraction process for most of the analytes on both sewage matrices, the one prepared on the laboratory and the sanitary one. The phases MIP2 and RAMIP1 presented a better performance for the extraction of analytes in effluents of a wastewater treatment plant. In conclusion, the matrix effect showed to be a persistent effect, given the complexity of the matrices analyzed. This fact is far from an ideal condition of detecting fluoroquinolones in real-life application where they are present at very low concentrations. In this sense, for the application of this method for real samples, a strategy of matrix matching would be needed during the validation of the method. (AU)

• FAPESP's process: 13/06294-6 - Evaluation of off-line and online microextraction for sample preparation of aqueous complex matrix containing fluoroquinolones and analysis by capillary liquid chromatography
• Grantee: Scarlet Nere Ortega
• Support Opportunities: Scholarships in Brazil - Doctorate