Determinação de poluentes orgânicos persistentes em amostras de água através da extração em fase micro-sólida dispersiva, seguida por cromatografia em fase gasosa com detecção por espectrometria de massas

Abstract

A significant amount of recently published papers has been shown an expressive advance in the synthesis and characterization of new and selective sorbents. However, there is a scarcity of papers reporting the development of new customized devices for the improvement of dispersive micro-solid phase extraction technique. In this work, it was developed analytical procedures for extraction/preconcentration of organic pollutants in water samples based on dispersive micro-solid phase extraction technique. For this purpose, new and effective devices were designed to perform extraction and micro-desorption steps. In the first developed procedure, the devices were employed in the extraction/preconcentration of polycyclic aromatic hydrocarbons from fresh and marine waters. The experimental conditions were optimized and the extraction parameters were set as 100 mg of C18, extraction by 32 min, and micro-desorption of 20 min with 500 μL of n-hexane. After validation, the analytical procedure provided limit of detection values ranging from 0.8 ng L-1 (Phenanthrene) a 1.70 μg L-1 (9,10-Phenanthrenequinone) and relative recoveries ranging from 59.1 % a 124 % (1-Methyl-6-Nitronaphthalene). The enrichment factor ranged from 39 (1,4-Naphthoquinone) to 400 (fluorene). The procedure was successfully applied in the determination of PACs in fresh and marine waters and their concentrations in the water samples ranged from 7.94 ng L-1 (Naphthalene) to 38.4 ng L-1 (Phenanthrene). An evaluation based on Analytical Ecoscale showed that the proposed procedure reached 92 % points, being considered an environmentally friendly procedure. In the second developed procedure, the extraction and microscale devices were employed in the extraction of pesticide residues from fresh and marine waters. The procedure was optimized through experimental design techniques and the optimal extraction conditions were: 30 min of extraction time, 6.74 % of NaCl added into 100 mL of the water sample, and 24 min of micro-desorption with 500 μL of ethyl acetate. The detection limits ranged from 0.51 ng L-1 (4,4-DDE) a 22.4 ng L-1 (dimethoate), and relative recoveries ranged from 74.2 % (endrin) to 123 % (molinate). In addition, it was obtained enrichment factor ranging from 72,5 (dimetoate) to 200 (tebuconazole). The analytical procedure was applied in the extraction of pesticide residues in fresh and marine waters. Pesticides such as malathion, dimethoate, and lambdacyhalothrin, which are commonly applied in Brazil, were detected in concentrations ranging from <LD to 120 ng L-1 (dimethoate). The third procedure consisted of the development of a Three Ways Device for Filtration and Solid-Liquid Microextraction. The prototype of a 3D imprinted device was assessed through preliminary experiments in the extraction of polycyclic aromatic hydrocarbons using 100 mL of a real water sample. The results showed that the prototype was successfully employed in the extraction steps and injections into GC-MS. However, it was obtained low enrichment factors for some PAHs, evidencing the need for additional adjustments on the device.