Rapid detection of endosulfan by a molecularly imprinted polymer microsphere modified quartz crystal microbalance
A highly selective and sensitive quartz crystal microbalance (QCM) fabricated by mixing with polyvinyl chloride and molecularly imprinted polymer microspheres (MIPMs) immobilized in situ on a piezoelectric quartz crystal (PQC) chip as a recognition element for rapid endosulfan detection in drinking water and milk samples. Based on our previous studies, we investigated the performances of the MIPMs in situ modified QCM (MIPMs-QCM). The surface microstructure of the uniform mono-layer MIPMs on a PQC chip was characterized by scanning electron microscope (SEM). It remained relatively stable within 10–20 min. The specificity of the MIPMs-QCM was also investigated by using a series of concentrations of endosulfan and structurally related analogs, which showed good selectivity and specificity for the recognition of endosulfan. Analysis by MIPMs-QCM sensor responded in the presence of different concentrations of endosulfan and demonstrated a good linear correlation over 10 to 40 ng mL−1 (y (Hz) = 30.83lg x (ng mL−1) − 26.32, R = 0.9856), and 40 to 1280 ng mL−1 (y (Hz) = 93.79lg x (ng mL−1) − 120.40, R = 0.9980), respectively. The lowest detection limit (LDL) was 5.59 ng mL−1 (S/N = 3). It could be repeated six times and stored for 6 months. Detection of endosulfan in water and milk samples was observed with recoveries of 96.0–104.1% and 101.8–108.0% respectively. The developed MIPMs-QCM is a reliable method for analysis of endosulfan with simple operation, good selectivity, and is inexpensive and reusable.