Molecularly imprinted stir bar sorptive extraction coupled with atomic absorption spectrometry for trace analysis of copper in drinking water samples

Abstract

In this work, a novel molecularly imprinted polymer (MIP) coated stir bar was fabricated and used for the extraction of trace amounts of Cu from drinking water. Cu–morin complex was used as template molecule which was chemically bonded to a glass stir bar and was employed for stir bar sorptive extraction of trace amounts of copper ions. The effects of different parameters such as pH, adsorption and desorption time, stirring rate, temperature and amount of ligand (morin) were evaluated on the extraction efficiency and the optimum conditions were established: the extraction and desorption times were fixed respectively at 20 and 30 min, mole ratio of ligand to the analyte was selected as 2, stirring speed was 700 rpm, pH was adjusted to 5 and the extraction process was performed at a temperature of 45 °C. Under these conditions, a pre-concentration factor of 25 was achieved and the total capacity of the stir bar for copper uptake was found to be 1200 μg. A non-imprinted polymer coating was used for comparison. The MIP stir bar showed sufficient mechanical and chemical stability and was able to perform more than 50 extractions without any damage to the polymer phase. The reproducibility between stir bars (n = 5) was 8.9%. The detection limit of the proposed method was found to be 0.38 μg L⁻¹ with a relative standard deviation within 0.56–5.3% and a dynamic range between 1 and 1000 μg L⁻¹. The method was successfully applied to the pre-concentration and determination of copper in a few different water samples.