Cold Vapor Atomic Absorption Determination of Hg in Crude Oil and Gasoline Samples after Solid Phase Extraction Using Modified Disks

Abstract

<em>A facile and highly efficient method have been developed for the preconcentration of the mercury content in crude oil and gasoline samples after digestion with microwave-assisted digestion. Octadecyl silica membrane disk has been modified by the recently synthesized triazene ligand, (E)-1-(2-ethoxyphenyl)-3-(4-nitrophenyl) triaz-1-ene (ENT), then the modified membrane was used for the preconcentration of mercury(II) ions and Cold Vapor Atomic Absorption Spectrometry (CV-AAS) have been used to determine the Hg (II) ion. Solution studies of ENT with a series of metal ions have been done in advance, and the results showed a strong affinity of ENT to the mercury ion. For solid phase extraction, pH of sample 6.0, flow rates 3.0 mL / min, enrichment factor 240, capacity of modified disk 690 µg Hg per 8.0 mg of ligand, eluent solvent 5.0 mL, 1.5M HClO₄, and the amount of the ligand 8.0 – 10.0 mg, have been optimized. A linear calibration curve has been obtained in the range of 0.80 – 65 µg / L with R² = 0.9991 and the Limit Of Detection (LOD) based on three times the standard deviation of the blank was 0.25 µg / L. The Relative Standard Deviation (RSD) for the determination of 50 mL aqueous solution containing 0.5 µg / LHg (II) found to be 1.0 % while a RSD value of 1.9% have been obtained for the determination of 0.1 µg / L Hg (II) (n=3). The characteristic concentration is 1.2 µg / Lin the original samples. The newly developed method was successfully applied to the determination of mercury ion in real crude oil samples, which are very important in environment and industries process.</em>