Use of 4-(2-pyridylazo)resocinol or 2-(2-pyridylazo)-5-dimethylaminophenol as chelating agent for determination of cadmium in seawater by atomic absorption spectrometry with on-line flow-injection sorbent extraction

Abstract

A home-made automatic on-line flow-injection sorbent extraction system for graphite furnace atomic absorption spectrometry (GFAAS) was used to determine Cd in seawater using octadecyl functional group (C 18) bonded silica gel as sorbent, 4-(2-pyridylazo)resocinol (PAR) or 2-(2-pyridylazo)-5-dimethylaminophenol (PADMAP) as chelating agent and methanol as eluent. The range of pH for the determination of Cd in seawater was 4.7–7.4 and 7.1–9.0 for using PAR and PADMAP as chelating agents, respectively. For the long-term stability studies, the complexes (PAR–Cd or PADMAP–Cd) are stable within the pH range 4.7–7.4 (for PAR) or 7.1–9.0 (for PADMAP) for 1 h at least. Sample volume of only 500–1000 μl was required to determine Cd in seawater. The simple calibration curve method was used and the detection limits of the determination of Cd in seawater were 4.0 and 1.7 ng l −1 for PAR and PADMAP as chelating agents, respectively. The sample throughput is 9–12 h −1. The accuracy and precision of the method were confirmed by the analysis of three kinds of certified reference saline water.