Dispersive Liquid Phase Microextraction (DLPME) as a Strategy for Cd^II Separation and Determination in High-Salinity Produced Waters by Graphite Furnace Atomic Absorption Spectrometry

In this study, we propose a microextraction method for the determination of Cd^II in produced waters. The process is based on the conversion of Cd^II ions into a hydrophobic diethyldithiocarbamate (DDTC) complex with its subsequent dispersive liquid phase microextraction (DLPME) from the aqueous medium with chloroform. The organic phase was then diluted with ethanol and Cd absorbance was measured by graphite furnace atomic absorption spectrometry (GF AAS). The experimental conditions related to the DLPME process were investigated, and the best microextraction conditions were achieved at pH = 6.0 (acetate buffer), 7.5 × 10^-6 mol L^-1 of DDTC, and when using 200 µL of chloroform as the extracting solvent. No dispersing solvent was needed, which allowed the recovery of approximately 140 µL of chloroform extract. Pyrolysis and atomization temperatures of the GF AAS program were determined through the construction of the respective curves. The estimated limits of detection (LOD) and quantification (LOQ) were 5 and 17 ng L^-1, respectively, whereas the enrichment factor for the method was 17. Six samples of seawater and five samples of produced waters with salinities between 30 and 270‰ were analyzed as well as two certified reference materials of saline waters.

Keywords:
produced waters; cadmium; dispersive liquid phase microextraction; saline waters