RESUMO
A simple, sensitive and reproducible solid-phase extraction method using plastic cartridges containing a monolithic sorbent (m-SPE), coupled to reverse phase liquid chromatography analysis, aiming to determine fifteen polycyclic aromatic hydrocarbons in surface water samples, was developed. The sorbent was easily prepared through a thermal polymerization reaction by using a mixture of n-butyl methacrylate as non-polar monomer and ethylene glycol dimethacrylate as crosslinker contained in a typical Polypropylene syringe cartridge. The effect of different parameters (type of hydrophobic monomer, elution solvent, sample volume, sorbent amount and sorbent load capacity) on the extraction efficiency was optimized. The optimal conditions were achieved by using n-butyl methacrylate as monomer, tetrahydrofurane (THF) as solvent for sorbent cleaning, THF:acetone (1:1) as elution solvent, 25.00 mL of sample volume, 600 µL of the polymerization mixture and 60 µg L-1 as sample loading capacity. Finally, the sorbent charge capacity, the reusability of the cartridges and the extraction efficiency of the m-SPE monolith, as compared with a typical C8 cartridge, were evaluated. Under the optimized experimental conditions, enrichment factors were between 76 and 103, relative recovery factors from 78 to 103%, accuracy values in the range of 58 to 98%, and inter-batch reproducibility values from between 2 and 10%, were obtained. The limits of detection and quantification were obtained by two different procedures: the signal to noise (S/N) ratios (3 and 10, respectively) and the IUPAC convention. The lowest LOD and LOQ values, obtained with the S/N ratios, were between 0.02 and 1.00 µg L-1, respectively whereas with the IUPAC convention the values were between 0.07 and 5 µg L-1. Using this procedure, several PAHs could be detected in the surface water sample taken from a river stream located in La Plata city (Buenos Aires Province, Argentina).
Assuntos
Hidrocarbonetos Policíclicos Aromáticos , Poluentes Químicos da Água , Cromatografia Líquida de Alta Pressão , Limite de Detecção , Polímeros , Reprodutibilidade dos Testes , Extração em Fase Sólida , Solventes , ÁguaRESUMO
A magnetic solid phase extraction technique followed by liquid chromatography with a fluorescence detector for naproxen analysis in human urine samples was developed. The method includes the extraction of naproxen with a magnetic solid synthetized with magnetite and poly 4-vinylpriridine, followed by the magnetic separation of the solid phase and desorption of the analyte with methanol. Under optimal conditions, the linear range of the calibration curve was 0.05-0.60 µg L-1, with a limit of detection of 0.02 µg L-1. In all cases values of repeatability were lower than 5.0% with recoveries of 99.4 ± 1.3%. Precision and accuracy values are adequate for naproxen (Npx) analysis in urine samples.