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Preconcentration

  • Graphene oxide-packed micro-column solid-phase extraction combined with flame atomic absorption spectrometry for determination of lead (II) and nickel (II) in water samples

    Graphene oxide-packed micro-column solid-phase extraction combined with flame atomic absorption spectrometry for determination of lead (II) and nickel (II) in water samples

    A b s t r a c t

    A sensitive and simple method has been established for simultaneous preconcentration of trace amounts of Pb (II) and Ni (II) ions in water samples prior to their determination by flame atomic absorption spectrometry. This method was based on the using of a microcolumn filled with graphene oxide as an adsorbent. The influences of various analytical parameters such as solution pH, adsorbent amount, eluent type and volume, flow rates of sample and eluent, and matrix ions on the recoveries of the metal ions were investigated. Using the optimum conditions, the calibration graphs were linear in the range of 7–260 and 5–85 μg L−1 with detection limits (3Sb) of 2.1 and 1.4 μg L−1 for lead and nickel ions, respectively. The relative standard deviation for 10 replicate determinations of 50 μg L−1 of lead and nickel ions were 4.1% and 3.8%, respectively. The preconcentration factors were 102.5 and 95 for lead and nickel ions, respectively. The adsorption capacity of the adsorbent was also determined. The method was successfully applied to determine the trace amounts of Pb (II) and Ni (II) ions in real water samples. The validation of the method was also performed by the standard reference material.

    Authors

    Hamid Shirkhanloo, Aisan Khaligh, Hassan Zavvar Mousavib and Alimorad Rashidi

    Results and discussion

    Based on the preliminary experiments, the retention of Pb (II) and Ni (II) ions on a GO-packed micro-column was chosen for preconcentration of the metal ions and their subsequent determination by FAAS. Hence, in order to obtain quantitative recoveries of Pb (II) and Ni (II) ions with good sensitivity and precision, the presented SPE system was optimised for various analytical parameters.

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  • Preconcentration and determination of heavy metals in water, sediment and biological samples

    Preconcentration and determination of heavy metals in water, sediment and biological samples

    A b s t r a c t

    In this study, a simple, sensitive and accurate column preconcentration method was developed for the determination of Cd, Cu and Pb ions in river water, urine and sediment samples by flame atomic absorption spectrometry. The procedure is based on the retention of the analytes on a mixed cellulose ester membrane (MCEM) column from buffered sample solutions and then their elution from the column with nitric acid. Several parameters, such as pH of the sample solution, volume of the sample and eluent and flow rates of the sample were evaluated. The effects of diverse ions on the preconcentration were also investigated. The recoveries were >95 %. The developed method was applied to the determination of trace metal ions in river water, urine and sediment samples, with satisfactory results. The 3δ detection limits for Cu, Pb and Cd were found to be 2, 3 and 0.2 μg dm-3, respectively. The presented procedure was successfully applied for determination of the copper, lead and cadmium contents in real samples, i.e., river water and biological samples.

     

     

     

     

    Authors

    Hamid Shirkhanloo, Ahmad Rouhollahi and Hassan Zavvar Mousavi

    CONCLUSIONS

     The developed procedure is very simple, sensitive and shows high tolerance to interference ions. Due to its good analytical characteristics, such as detection limit, enrichment factor and precision, the method is suitable for trace element analysis. In addition, no modification or functionalization of the employed adsorbent is required. The recoveries of the studied analytes were nearly quantitative. The accuracy of the results was verified by analyzing a certified reference material and spiked water samples. The recoveries for these elements were very satisfactory, which evidence for the reliability of the proposed method in the analysis of real samples.

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     lead; copper; cadmium; mixed cellulose ester membrane; preconcentration

  • Preconcentration and Determination of Trace Amount of Nickel in Water and Biological Samples by Dispersive Liquid–Liquid Microextraction

    Preconcentration and Determination of Trace Amount of Nickel in Water and Biological Samples by Dispersive Liquid–Liquid Microextraction

    A b s t r a c t

    Anew, simple and highly sensitive dispersive liquid–liquid microextraction method using a ionic liquid, i.e., 1-Butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]) for nickel determination at trace levels in real samples was developed. Nickel was chelated with diethyl dithiocarbamat reagent and extracted into an ionic liquid. Ni was back-extracted from the IL phase with 200 L of 0.5 mol L-1 nitric acid and determined by electrothermal atomic absorption spectrometry (ETAAS). Various parameters such as pH, amount of ionic liquid, eluent type and volume, chelating agent concentration, volume of the sample solution and matrix interference effect on the recovery of the metal ions have been studied. Under the optimum conditions, the enrichment factor 100 was obtained from only 20 mL of sample. The calibration graph was linear in the rage of 20-700 ng L-1 of nickel with detection limit of 5 ng L-1. The relative standard deviation (R.S.D.s) for eight replicate measurements of 20 ng L-1 of nickel was 5.6%. Validation of the methodology was performed by standard addition method and analysis of certified reference material. The method was successfully applied to the determination of Ni+2 in serum and tap water samples.

     

     

     

    Authors

    Hamid Shirkhanloo, Ahmad Rouhollahi and Hassan Zavvar Mousavi

    ACKNOWLEDGEMENTS

    The financial support of this work by K. N. Toosi University of Technology and Semnan University Research Council are greatly acknowledged

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  • Simultaneous Preconcentration and Determination of Trace Amount of Lead and Copper in Water Samples by Flame Atomic Absorption Spectrometry

    A b s t r a c t

    In the present paper, a simple and sensitive method for simultaneous preconcentration and determination of lead and copper by flame atomic absorption spectrometry was developed. This method was based on solid phase extraction of lead and copper with 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on naphthalene column. After preconcentration stage, the column was eluted by 5 mL of 1.2 mol L-1 nitric acid solution and metal ions directly determined by flame atomic absorption spectrometry. The effect of different variables such as pH, sample volume, amount of chelate, flow rate and eluent solution on the recovery of the analyte was investigated. The detection limits were 0.7 and 0.5 μg L-1 for lead and copper, respectively. The relative standard deviations of the determinations for analyte ions were below 4 %. This procedure was applied to the determination of lead and copper in water samples. The results demonstrated that the procedure can be applied for analysis of waters with satisfactory accuracy.

    Authors

    H. ZAVVAR MOUSAVI and H. SHIRKHANLOO

    ACKNOWLEDGEMENT

    The financial support of this work by Semnan University Research Council is greatly acknowledged.

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  • Ultra-Trace Silver Determination in Biological and Water Samples by Electrothermal Atomic Absorption Spectrometry after Electrodeposition on a Graphite Probe

    Ultra-Trace Silver Determination in Biological and Water Samples by Electrothermal Atomic Absorption Spectrometry after Electrodeposition on a Graphite Probe

    A b s t r a c t

    Arapid and simple procedure was developed for selective and sensitive determination of ultra-trace silver in biological and environmental samples using the electrodeposition on a graphite probe modified with palladium followed by electrothermal atomic absorption spectrometry. Several experimental parameters for the electrodeposition, such as deposition potential, electrolyte concentration, pH of solution and deposition time were optimized. The calibration graph after preconcentration was linear in the range of 10-250 ngL–1 with correlation coefficient of 0.9989 under the optimum conditions for procedure. The limits of detection (LOD) and quantification (LOQ) base on (3σ) and (10σ) were 2.8 ngL–1 and 9.4 ngL–1 respectively. Related standard deviation (RSD) for eight replicatemeasurements of 100 ngL–1 silver was 4.3%. Samples were digested completely in a closed microwave digestion system using only perchloric acid, and interference owing to various cations was also investigated. The proposed procedure was successfully applied to determine silver in blood, urine and some environmental samples with satisfactory analytical results.

     

     

     

    Authors

    Reza Moradkhani, Ahmad Rouhollahi, Hamid Shirkhanloo and Jahan Ghasemi

    CONCLUSIONS

    Results presented in this work demonstrate an effective approach to improve the detection limit of ETAAS for silver determination. This procedure is very selective and shows high tolerance to interferences from complex matrix due to electrodeposition step. Also, the proposed method is easy, safe, rapid and inexpensive for preconcentration and separation of ultra-trace silver and determination by ETAAS in environmental and biological samples.

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  • Utilization of electrodeposition on a graphite probe modified with palladium in determination of lead by graphite furnace atomic absorption spectrometry in water and environmental samples

    Utilization of electrodeposition on a graphite probe modified with palladium in determination of lead by graphite furnace atomic absorption spectrometry in water and environmental samples

    A b s t r a c t

    In this work a rapid and selective procedure for separation and preconcentration of lead (Pb2+) before determination by electrothermal atomic absorption spectrometry (ETAAS) was developed. The procedure is based on the electrodeposition on a graphite probe modified with palladium. The lead was deposited from acetate buffer solution at pH 5.5. Various parameters, such as pH of solutions, deposition potential, buffer concentration, stirrer speed, time of deposition and temperature program, were optimized. After optimization of the conditions, detection limit 17 ng L–1 by 3 σ, and enrichment factor 61 were achieved for 2 min electrodeposition time and improved as deposition time was increased. Linearity of calibration was kept between 0.05-0.50 μg L–1 with a correlation coefficient of 0.9979 and suitable precision, R.S.D. % = 5.1 (n = 8). Samples were digested completely in a closed microwave digestion system using only perchloric acid, and interference owing to various cations was also investigated. The procedure was successfully applied to determine the presence of lead in rice, radish, okra, onion and water samples.

     

     

     

     

    Authors

    Reza Moradkhani, Ahmad Rouhollahi , Hamid Shirkhanloo, Jahan B. Ghasemi

    Conclusion

    The results obtained in this work demonstrate an effective approach to improve the detection limit of ETAAS for lead determination. The method due to advantages such as high sensitivity, low detection limit and high tolerance limit of common ions is a powerful tool for rapid and sensitive determination of lead in complex matrixes. Also, the proposed method is easy, safe and inexpensive for preconcentration and separation of lead and determination by ETAAS in environmental samples.

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