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

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 / L Hg (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 / L in 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.