Cr(VI) determination in seawater samples using an on-line sorption preconcentration in a knotted reactor coupled with electrothermal atomic absorption spectrometry

Abstract

An on-line flow injection sorption preconcencentration in a knotted reactor coupled with electrothermal atomic absorption spectrometry (FI-KR-ETAAS) has been developed to determine chromium(VI) in seawater samples. The on-line complex formation between Cr(VI) and ammoniumpirrolidindithiocarbamate (APDC) was performed and the complex retained on the inner wall of the KR. Variables affecting the sorption preconcentration process, such as pH, APDC amount, load flow rate, preconcentration time, concentration, and volume of washing solution, KR length, elution volume, and interferences, were studied. The complex was eluted with 40 μL of ethanol and introduced directly into the graphite furnace. A preconcentration factor of 31 was obtained. The detection limit (3SD) was 7 ng L-1. The precision (RSD n = 11) was 4.4% at 0.2 (μg L-1. and the recovery was 99.3 ± 1.70%. The method was applied to the Cr(VI) determination in seawater samples from the Ria de Arousa Estuarine in Galicia (Northwestern Spain), resulting in Cr(VI) concentrations ranging from 0.03 - 0.09 μg L-1.