Abdolmohammad-Zadeh, Hossein,
Rezvani Z.,
Sadeghi, G.,
Zorufi E. 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.
Analytica Chimica Acta (18734324)(2)
A simple dispersive liquid-liquid microextraction methodology based on the application of 1-hexylpyridinium hexafluorophosphate [HPy][PF6] ionic liquid (IL) as an extractant solvent was proposed for the preconcentration of trace levels of zinc as a prior step to determination by flame atomic absorption spectrometry (FAAS). Zinc was complexed with 8-hydroxyquinoline (oxine) and extracted into ionic liquid. Some effective factors that influence the microextraction efficiency such as pH, oxine concentration, amount of IL, ionic strength, temperature and centrifugation time were investigated and optimized. In the optimum experimental conditions, the limit of detection (3 s) and the enhancement factor were 0.22 μg L-1 and 71, respectively. The relative standard deviation (RSD) for six replicate determinations of 13 μg L-1 Zn was 1.92%. In order to validate the developed method, a certified reference material (NIST SRM 1549) was analyzed and the determined values were in good agreement with the certified values. The proposed method was successfully applied to the trace determination of zinc in water and milk samples. © 2009 Elsevier B.V. All rights reserved.
