The liquid phase microextraction (LPME) was combined with the modified Graphite furnace atomic absorption spectrometry (GF-AAS) for determination of lead in the water and solid samples. In a preconcentration step, lead was extracted from a 2 ml of its aqueous sample in the pH = 5 as lead-Pyrimidine-2-thiol cationic complex into a 4 µl drop of 1,2 dichloroethane and ammonium tetraphenylborate as counter ion immersed in the solution. In the drop, the lead-Pyrimidine-2-thiol ammonium tetraphenylborate ion associated complex was formed. After extraction, the microdrop was retracted and directly transferred into a graphite tube modified by [W.Pd.Mg] (c). Some effective parameters on extraction and complex formation, such as type and volume of organic solvent, pH, concentration of chelating agent and counter ion, extraction time, stirring rate and effect of salt were optimized. Under the optimum conditions, the enrichment factor and recovery were 525% and 94%, respectively. The calibration graph was linear in the range of 0.01 -12 µg·L -1 with correlation coefficient of 0.9975 under the optimum conditions of the recommended procedure. The detection limit based on the 3S b criterion was 0.0072 µg·L -1 and relative standard deviation (RSD) for ten replicate measurement of 0.1 µg·L -1 and 0.4 µg·L -1 lead was 4.5% and 3.8% respectively. The characteristic concentration was 0.0065 µg·L -1 equivalent to a characteristic mass of 26 fg. The results for determination of lead in reference materials, spiked tap water and seawater demonstrated the accuracy, recovery and applicability of the presented method.
A method for the determination of trace amount of cadmium ion after preconcentration by extracting its dithizone complex into molten naphthalene was developed. Several experimental conditions such as pH of the solution, stirring time, the amounts of naphthalene, standing time and volume of the solution were optimized. Trace amount of cadmium ion in aqueous solution of sample was chelated with 5 mL of 0.001 M dithizone at pH 8. After addition of 0.15 g naphthalene, the solution was heated to about 85 o C and stirred (800 rpm) for 2 min to reproduce the microcrystalline naphthalene. Cadmium ion was determined by a graphite furnace atomic absorption spectrometer. The interfering effects of diverse concomitant ions (cations and anions) were investigated. Artificial sea water and a standard reference material (SRM) were analyzed by this method. The sensitivity and detection limit of 1.2 ngL-1 and 1.5 ng L-1 were found, respectively.
An accurate, rapid, simple, and novel technique was developed to determine simvastatin (SMV). In this research, a screen-printed electrode (SPE) was deposited with graphene oxide (GO) and sodium dodecyl sulfate (SDS), respectively. For the first time, the handmade modified SPE measured the SMV by differential pulse voltammetry (DPV) with high sensitivity and selectivity. The results of cyclic voltammetry indicated the oxidation irreversible process of SMV. Various parameters (pH, concentration, scan rate, support electrolyte) were performed to optimize the conditions for the determination of SMV. Under the optimum experiment condition of 0.1 M KNO3 as support electrolyte and pH 7.0, the linear range was achieved for SMV concentration from 1.8 to 36.6 µM with a limit of detection (LOD), and a limit of quantitation (LOQ) of 0.06 and 1.8 µM, respectively. The proposed method was successfully utilized to determine SMV in tablets and urine samples with a satisfactory recovery in the range of 96.2 to 103.3%.
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