Mechanics of Materials
Mechanics of Composite Materials
Advanced Mathematics
Articles
Publication Date: 2013
Microchimica Acta (14365073)(7-8)
We have used a nano-structured nickel-aluminum layered double hydroxide (Ni-Al LDH) for the extraction of trace levels of selenium prior to its determination by continuous-flow hydride generation atomic absorption spectrometry. Extraction is based on the adsorption of Se(IV) anions on the Ni-Al-nitrate LDH, and/or their exchange with the nitrate anions in the LDH interlayer. The effects of pH value, amount of nanosorbent, eluent type and concentration, sample volume and flow rate were optimized. No appreciable matrix effects were observed. Under optimum conditions, the limit of detection (defined as three times the standard deviation of the blank signal divided by the slope of the calibration plot) is 10 pg mL-1, and the relative standard deviation is 2.8 %. The sorption capacity and preconcentration factor are 10 mg g-1 and 33, respectively. The method was successfully applied to the determination of Se(IV) in tap water, river water, well water, wastewater and oyster tissue (certified reference material, CRM 1566b). © 2013 Springer-Verlag Wien.
Publication Date: 2013
Journal of the Serbian Chemical Society (03525139)(1)
A simple micelle-mediated phase separation method has been developed for the pre-concentration of trace levels of iron as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The method is based on the cloud point extraction (CPE) of iron using the non-ionic surfactant poly(ethyleneglycol-mono-p-nonylphenylether) (PONPE 7.5) without the addition of any chelating agent. Several variables affecting the extraction efficiency were studied and optimized utilizing a central composite design (CCD) and a three-level full factorial design. Under the optimum conditions, the limit of detection (LOD), limit of quantification (LOQ) and preconcentration factor were 1.5 μg L-1, 5.0 μg L-1 and 100, respectively. The relative standard deviation (RSD) for six replicate determinations at 50 μg L -1 Fe(III) level was 1.97 %. The calibration graph was linear in the range of 5-100 μg L-1, with a correlation coefficient of 0.9921. The developed method was validated by the analysis of two certified reference materials and applied successfully to the determination of trace amounts of Fe(III) in water and rice samples.
Publication Date: 2012
Talanta (00399140)
A simple solid phase extraction system based on the applying the nickel-aluminum layered double hydroxide (Ni-Al LDH) as a nano-sorbent was developed for the speciation analysis of chromium and manganese by flame atomic absorption spectrometry (FAAS). The method is based on the fact that Cr(VI) and Mn(VII) oxyanions could be adsorbed on the Ni-Al(NO3-) LDH and/or exchanged with LDH interlayer NO3- ions at pH 6.0, whereas Cr(III) and Mn(II) cations pass through the LDH-packed column without retention. The determinations of total Cr and Mn, and hence indirectly Cr(III) and Mn(II), involve the pre-oxidations of Cr(III) and Mn(II) to Cr(VI) and Mn(VII) with H2O2 and acidic solution of KIO4, respectively. Several important factors affecting the retention efficiency were investigated and optimized. In the optimum experimental conditions, the limits of detection (3Sb/m) for Cr(VI) and Mn(VII) were 0.51 and 0.47 ng mL-1, and the relative standard deviations were 2.5 and 3.2% (C = 30.0 ng mL-1, n = 6), respectively. The presented method was validated by the analysis of a certified reference material, and applied to the speciation of Cr and Mn in drinking waters, surface waters and industrial wastewater effluents. © 2012 Elsevier B.V. All rights reserved.
Publication Date: 2011
Analytica Chimica Acta (18734324)(2)
The nickel-aluminum layered double hydroxide (Ni-Al LDH) was synthesized by a simple co-precipitation method with controlled pH and followed by hydrothermal treatment. The obtained nano-structured inorganic material was employed, for the first time, as a new solid-phase extraction (SPE) sorbent for the extraction and pre-concentration of trace levels of fluoride ions from aqueous solutions. An indirect method was used for monitoring of extracted fluoride ions. The method is based on the quenching effect of extracted fluoride ions upon the fluorescence intensity of Al-oxine complex via the forming of AlF63-, which was determined spectrofluorometrically at λem=510nm with excitation at λex=404nm. The effect of several parameters such as type of interlayer anion in Ni-Al LDH structure, pH, sample flow rate, elution conditions, amount of nano-sorbent, sample volume and co-existing ions on the extraction efficiency of the analyte were investigated. The results showed that fluoride ions could be retained on the Ni-Al (NO3-) LDH at pH 6.0 and stripped by 1.2mL of 3.0molL-1 NaOH. In the optimum experimental conditions, the limit of detection (3s) and enrichment factor were 9.0ngmL-1 and 50, respectively. The optimized method was successfully applied to the determination of fluoride concentration in various water samples. The results obtained from the proposed method were successfully compared with those provided by standard SPADNS method. © 2010 Elsevier B.V.
In this research, we combined ionic liquid-based dispersive liquid-liquid micro-extraction (IL-based DLLME) with stopped-flow spectrofluorometry (SFS) to evaluate the concentration of aluminum in different real samples at trace level. 1-Hexylpyridinium hexafluorophosphate [Hpy][PF6] ionic liquid and 8-hydroxyquinoline (oxine), which forms a highly fluorescent complex with Al3+, were chosen as the extraction solvent and chelating agent, respectively. The hydrophobic Al-oxine complex was extracted into the [Hpy][PF6] and separated from the aqueous phase. Then, the concentration of the enriched aluminum in the sediment phase was determined by SFS. Some effective parameters that influence the SFS signals and the micro-extraction efficiency, such as the suction and sending time, the concentration of the chelating agent, pH, the amount of the ionic liquid, the type of disperser solvent and diluting agent, ionic strength, extraction time, equilibration temperature and centrifugation time were investigated and optimized. In the optimum experimental conditions, the limit of detection (3 s) and enrichment factor were 0.05 μg L-1 and 100, respectively. The relative standard deviation (RSD) for six replicate determinations of 6 μg L-1 Al was 1.7%. The calibration graph using the pre-concentration system was linear in the range of 0.06-15 μg L-1 with a correlation coefficient of 0.9989. The developed method was validated by the analysis of certified reference materials and applied successfully to the determination of aluminum in several water, fruit juice and food samples. © 2010 Elsevier B.V. All rights reserved.
