The synthesis of 8-hydroxyquinoline bonded silica and its application by flow injection-indutively coupled plasma-mass spectrometry on the detection of trace metals lead in sea water

Abstract

A new method for the synthesis of 8-hydroxyquinoline (8-HQ) bonded silica (SHQ) for metal chelation applications has been developed. The new synthetic route has been compared with the conventional one reported in the literature in terms of reaction yield, product performance and operational ease. The new method is based on a one-step Mannich reaction, and an orthogonal experimental design has been used for process optimization. The 8-HQ bonded silica product obtained has been characterized by diffuse reflectance infrared Fourier transform ( DRIFT) spectroscopy, and the presence of a strong absorption band of the phenol-OH near 1380 cm(-1) indicates the successful bonding of 8-HQ on silica surface. The concentration of 8-HQ bonded to the silica surface quantified by ultroaviolet-visible spectroscopy is 542 mu mol/g, much higher than the product obtained by the conventional synthetic route, which is 117 mu mol/g. The dynamic binding capacities of the two SHQs towards copper (II) has been measured and compared by inductively coupled plasma mass spectrometry (ICP-MS),and the results are 347 mu mol/g for the new SHQ and 76 mu mol/g for the conventional one. The results demonstrate that the new method is not only simpler and more convenient operationally, but also produced product with better performance. The SHQ synthesized has been used for measuring trace lead in seawater and estuary water samples using on-line flow injection (FIA)-ICP-MS. The detection limit of the method is about 10 ng/L, and the relative standard deviation (s(r)) is 9.1%. Using CASS-4 standard seawater samples spiked with Pb standard, the recovery of Pb from the process is about 140%. The high recovery observed is likely due to the contamination of Pb in the high purity nitric cid used in the experiments.