Iranian Journal of Analytical Chemistry
Volume:5 Issue: 1, Winter and Spring 2018

A preconcentration procedure, based on the coprecipitation of Mn2+, Co2+, Ni2+, Cd2+ and Cu2+ ions using a new organic coprecipitant, (2-(4-{[(4-{5-oxo-4-[1-(2-thienyl) methylidene]- 4,5-dihydro- 1,3- oxazole-2-yl} phenyl) imino] methyl} phenyl) methylidene ] amino} phenyl) -4-[ 1-phenyl methylidene] -1,3-oxazole-5(4H)-one (OTMDO) without adding any carrier element has been developed. The resultant concentrated elements were determined by using flame atomic absorption spectrometer. The influences of some analytical parameters including pH, amount of the coprecipitant, standing time, centrifugation rate and time, sample volume and diverse ions were investigated on the quantitative recoveries of analyte ions. Under the optimized experimental conditions, the calibration curves for the analyte ions were studied. The relative standard deviations for seven replicate determinations of a mixture of 0.1 mg mL−1 Mn2+, Co2+, Ni2+, Cd2+ and Cu2+ ions in the original solution were 2.5, 2.4, 2.2, 2.1 and 2.5%, respectively. The detection limits based on 3Sb/m for Mn2+, Co2+, Ni2+, Cd2+ and Cu2+ ions in the original solution were 1.2, 1.3, 1.2, 0.6 and 1.5 ng mL−1, respectively. The proposed method has been applied for determination of trace amounts of the analyte ions in the standard, water samples; brewed tea; tobacco samples and satisfactory results were obtained.

A kind of ferrocene mediated enzymatic biosensor was fabricated in order to the measurement of glucose as an important biological analyte. A homogenous mixture of ferrocene including Chitosan(CS), Nafion(Nf) and an imidazolium based ionic liquid, 1-butyl-3-methyl imidazoliumhexafluorophosphate, [BMIM]HF6PO4, was prepared. The mentioned mixture was cast on the surface of carbon ceramic electrode and an enzymatic layer was entrapped between two layers of this mixture in order to improving the mechanical stability of the biosensor. Cyclic voltammetry and chronoamperometry were used to investigate the analytical performance of the biosensor. Remarkable deduction of interfering signals produced by AA and UA was obtained by applying a constant potential (180mV) on the human plasma for a short period of time (100min). Values of practical parameters such as sensitivity (2.73 µA mM-1cm-2), linear range (95.23–1367.5 µM) and detection limit (48 µM) were obtained by the chronoamperometric studies. The apparent Michaels-Menten constant, Km (3.52 mM) was also calculated. In order to estimate the practical accuracy and precision of the enzymatic biosensor, a test of spiked glucose solution recovery in natural plasma was done.

An efficient carbon dot-dispersive liquid-liquid microextraction followed by UV-Vis spectrophotometry (CD-DLLME-UV-Vis) has been effectively developed for the sensitive determination of 1,3,6,8-tetranitrocarbazole (TNC) in environmental water samples. In this DLLME-based method, home-made syntheses carbon dots (CDs) were directly extracted into carbon tetrachloride using trioctylmethylammonium chloride (aliquat 336), which works as a disperser agent. By applying inherent colorimetric feature, the enriched CDs exhibited an intensive absorption signal at 300 nm, which swelled up in the presence of TNC due to their interaction at the colloidal interface. Main parameters that controlling and affecting the performance of the microextraction process were evaluated and optimized in details. An enrichment factor of 55.5 beside a meaningful sample clean-up was achieved under the optimized conditions. The calibration curve was linear in the range of 1-200 ng mL-1 with regression coefficient corresponding to 0.999. Limit of detection (S/N = 3) was 0.2 ng mL-1 while the RSD% values (n = 10) for the target analyte at two concentration levels of 20 and 100 ng mL-1 were 3.6 and 1.7, respectively. The proposed method was ultimately exerted for the preconcentration and determination of TNC in various environmental water samples and admissible results were achieved.

Hollow fiber-solid phase microextraction (HF-SPME) technique containing multiwalled carbon nanotubes (MWCNTs) reinforced sol-gel nanocomposite coupled with UV–Vis spectrophotometry was applied for preconcentration and determination of lead, zinc and silver in water samples. In this technique, a high efficiency sorbent containing mixture of MWCNTs and a microporous gel was injected into a piece of a polypropylene hollow fiber for in situ gelation. The method validation was included and satisfying results were obtained. It owes large surface area and porosity of the nano-adsorbent. Under the optimal conditions, linear calibration curves were established for the concentration of Pb2+, Zn2+ and Ag+ in the range of 0.2–7.0, 0.3–7.0 and 2.0–50 µg/mL respectively. The limits of detection were 0.032, 0.057 and 0.325 µg/mL for Pb2+, Zn2+ and Ag+. The relative standard deviations (RSDs) were found to be less than 8.0 %.

Polyaniline/maghemite magnetic nanocomposite (PANI/γ -Fe2O3 MNC) was used as active agents for removal of lead ions from aqueous media. Chemical co-precipitation method was used to prepare the maghemite nanoparticles. Subsequently, the MNC was synthesized through polymerization of aniline. It was characterized by FT-IR.The efficiency of this MNC was estimated for Pb (II) removal by using batch method. The results showed that optimum conditions for lead removal were found to be at pH of 6, adsorbent dosage of 0.04 g and equilibrium contact time of 90 min. The kinetic of adsorption system have been studied based on the assumption of a pseudo-second order rate law. The adsorption isotherms were examined. The Freundlich adsorption isotherm model was found to represent the equilibrium adsorption isotherm better than Langmuir isotherm. The thermodynamic studies indicated that the adsorption was spontaneous and endothermic process for lead.

Carbon nanofibers (CNFs) and carbon nanorods (CNRs) are synthesized using coal particles (