Analytical and Bioanalytical Chemistry Research
Volume:2 Issue: 1, Winter - Spring 2015

The application of sulfur nanoparticles as an efficient adsorbent for the solid-phase extraction and determination of the trace amounts of Pb and Pd ions was investigated in environmental samples using flame atomic absorption spectrometry. Effects of various parameters such as pH, flow rate of sample and eluent, type and concentration of eluent, sample volume, amount of adsorbent and interfering ions were investigated and optimized. The results showed that the optimal conditions for quantitative recovery of the metal ions by adsorption and elution on the sulfur nanoparticles were achieved by employing a flow rate of 2 ml min-1, a pH of 9.5 for the sample solutions, and an eluent composed of 4.0 M HNO3 in ethanol. The maximum adsorption capacity of SNPs as sorbents at optimum conditions for lead and palladium ions was found to be 2.80 mg g-1 and 2.87 mg g-1, respectively. At optimum conditions, the detection limits of this method were 0.3 and 2.5 ng ml-1 for Pb(II) and Pd(II), respectively. The proposed procedure was applied to the determination of the metal ions in soil and water samples.

A simple, rapid and sensitive solvent assisted-dispersive solid phase extraction method was developed for the extraction of iron(II) prior to its spectrophotometric determination. The Fe(II) reacted with 2,4,6-tris(2-pyridyl)-1,3,5-triazine, neutralized with sodium dodecyl sulfate and extracted onto the fine particles of benzophenone which were formed upon rapid injection of a mixture of benzophenone as the sorbent and ethanol as the disperser solvent into the aqueous solution. After phase separation, the sedimented phase containing the complex was dissolved in ethanol and the analyte concentration was determined by measuring its absorption at 594 nm. Total iron was determined after the reduction of Fe(III) to Fe(II) with hydroxylamine hydrochloride. Under the optimized conditions, an enhancement factor of 32, the detection limit of 0.16 µg l-1, and the relative standard deviation of 1.9% (n = 6) at 20 µg l-1 concentration level of Fe(II) were achieved. The method was successfully applied to the determination of iron species in water samples and total iron in infant dry formula milk, apple, rice, spinach and parsley samples.

The present work concerns on the investigation of the role of polyethylene glycols (PEGs) as masking agent for amelioration of extraction-separation of La(III), Eu(III) and Er(III) ions by the acidic extractant bis(2-ethylhexyl)phosphoric acid (DEHPA). The studied solvent extraction system is based on the combination of chelating effect of DEHPA in the organic phase on the one hand, and the binding properties of the PEGs in the aqueous phase, on the other hand, to provide an improvement in separation of La(III), Eu(III) and Er(III) ions. The first part of this study deals with effect of diluent used as organic solvent on the separation efficiency of bis(2-ethylhexyl)phosphoric acid towards lanthanum, europium and erbium ions. Then, the influence of the presence of three polyethylene glycols, with molecular weights 200, 400 and 2000 (PEG200, PEG400 and PEG2000), in the aqueous phase on the separation of the studied metal ions was evaluated and discussed.

The net analyte signal standard addition method was used for simultaneous spectrophotometric determination of sertraline and fluoxetine in pharmaceutical preparations. The method combines the advantages of the standard addition method with the net analyte signal concept to enable the extraction of information about an analyte from the spectra of multi-component mixtures. This method uses full spectrum realization and does not require calibration and prediction steps. Determination requires only a few measurements. The limit of detection for fluoxetine was 0.31 µg ml-1 and for sertraline was 0.20 µg ml-1. The root mean square error for fluoxetine was 0.45 and for sertraline was 0.39.

A spectrophotometric method for selective complexation reaction and simultaneous determination of mycophenolate mofetil (MPM), and mycophenolic acid (MPA) using three multivariate chemometric methods, i.e. partial least squares regression, principal component regression and principal component artificial neural networks, is proposed. The method is based on the complexation reaction of MPM and MPA with Fe(III) ion in the solution. A nonionic surfactant, Triton X-100, was used for dissolving the complexes and intensifying the signals. The linear determination ranges for the determination of MPA and MPM were 5.0-215.0 mg l-1, and 10.0-1000.0 mg l-1, respectively. The detection limit for MPA and MPM was obtained as 0.3 mg l-1 and 1.1 mg l-1, respectively. Satisfactory results were obtained by the combination of spectrophotometric method and chemometrics techniques. The method was successfully applied to the simultaneous determination of MPM and MPA in serum sample and the results were comparable with HPLC method.

A simple and sensitive chemiluminescence-based method was established for the determination of rabeprazole.The proposed method was based on the enhancing effect of rabeprazole on Ce(IV)-Na2SO3 -Tb(III) chemiluminescence reaction. A possible mechanism was discussed for chemiluminescence system by studying UV-Vis, fluorescence and chemiluminescence spectra. The effects of various chemical parameters were investigated and optimized. Under the optimum conditions, the enhanced chemiluminescence intensity was directly proportional to the concentration of rabeprazole in the range of 0.015-0.2 µg ml-1, with a detection limit of 6 ng ml-1. The proposed method was applied to the analysis of pharmaceutical formulations and human plasma samples and to the dissolution study of rabeprazole tablets with satisfactory results. The results indicated that more than 95% of the labeled amount of rabeprazole was dissolved over 30 min in the basic medium, while only 10% of rabeprazole was released in acidic medium.

In this research, a rapid, reliable and selective dispersive liquid-liquid microextraction (DLLME) followed by direct injection of microdroplet to graphite furnace atomic absorption spectrometry (GF-AAS) method for the determination of ultra-trace amounts of Ag(I) was developed. Effect of the important experimental parameters on the extraction efficiency of Ag(I) was investigated using response surface methodology (RSM) by performing a central composite design (CCD). A newly synthesized Calixarene (mesotetraspirocyclohexylcalix[4]pyrrole, TSCC4P) was utilized as the chelating agent. The optimal experimental condition was obtained as sample volume: 5 ml, dispersive solvent type: methanol, dispersive solvent volume: 715 μl, extracting solvent: 1,2-dichlorobenzene, volume of extracting solvent: 25 µl, amount of TSCC4P: 127.1 µg, and pH of sample solution: 6.5. Under the optimum conditions Ag(I) ions were extracted into a fine sedimented microdroplet, which 10 µl of it was directly injected into GF-AAS system. The calibration graph was linear over the range of 0.1-10.0 ng ml-1 with a detection limit (S/N = 3) of 0.02 ng ml-1. The relative standard deviation (RSD%) for ten replicated determinations of 10 ng ml-1 Ag(I) was 3.1%. The enrichment factor and extraction recovery were found to be 292 and 96%, respectively. The proposed DLLME-GF-AAS method was successfully applied to the extraction and determination of Ag(I) ions in different real water samples.