Analytical and Bioanalytical Chemistry Research
Volume:4 Issue: 2, Summer - Autumn 2017

In this paper, magnetically multiwalled carbon nanotubes (MMWCNTs) nanocomposite modified by methyl-2-[2-(2-2-[2-(methoxycarbonyl) phenoxy] ethoxyethoxy) ethoxy] benzoate was applied for magnetic solid-phase extraction (MSPE) of thallium(I) ions. Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) spectrometry and vibrating sample magnetometer (VSM) were used to characterize the magnetic sorbent. The effects of as pH, sample volume, eluent, and interfering ions were studied. Under the optimized conditions, the preconcentration factor of 100 and the linear response over 3−280 µg L−1 were obtained. The detection limit of the suggested procedure (LOD, 3Sb/m) was found to be 0.59 µg L−1. The relative standard deviation for six replicate detection of 100 µg L−1 of Tl(I) was ±1.9%. Finally, the developed method was utilized for the determination of thallium(I) ions in different real samples with recoveries in the range of 96.9–102.2% for the spiked samples. The proposed MSPE method exhibited some advantages, such as simplicity, rapidity, high sensitivity and excellent precision. In addition, the mechanism of thallium extraction by modified nanocomposite was proposed.

In this study, Multi-walled carbon nanotube-CO-NH(CH2)2NH-SO3H was prepared through the functionalization of commercial multi-walled carbon nanotubes in three steps and then it was characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). In addition, the adsorption of Methylene Blue was investigated by using these nanotubes. In order to remove dye, the effects of different parameters including stirring time, pH value, the initial concentration of dye, and the amount of carbon nanotubes were studied. More than 99.5% of dye was removed at neutral pH within a short time. Pseudo-second-order equation was predicted by adsorption kinetic. Different isotherms were studied to define adsorption mechanism and Langmuir model showed the best result compared with other isotherms. This project offers a facile and efficient adsorption method for removing Methylene Blue from aqueous solution. Short stirring time, neutral pH and high qmax (the maximum adsorption capacity in saturated single layer) are the significant characteristics of this research.

An efficient, sensitive and fast method was developed based on an ultrasound-assisted extraction followed by an ion-pair dispersive liquid-liquid microextraction (USAE-IP-DLLME) for the simultaneous determination of five commonly used synthetic sulfonate dyes (tartarazine, quinoline yellow, sunset yellow, azorubine, and brilliant blue) in ice cream samples using high performance liquid chromatography. First, important parameters on USAE and samples clean-up were investigated and optimized. Then, some effective parameters on DLLME were studied and optimized. Under the optimum conditions, good linearity (0.5–1000 µg L-1, > r2=0.99) were obtained for the dyes. Limits of detection and limits of quantization were in the range of 0.01–0.05 µg L-1 and 0.03–0.15 µg L-1, respectively. The recoveries of the five synthetic colorants ranged from 90.3 to 109.7%. Intra (1.4–6.4%) and inter-day precision (3.9–9.7%) expressed as relative standard deviation (RSD) at 10 and 100 µg L-1 levels less than 10% were also achieved. Finally, this method has been applied successfully in the determination of the colorants in the ice cream samples.

A simple, rapid and efficient method has been developed for the extraction, preconcentration and determination of cobalt (II) and nickel (II) ions in water samples by air-assisted liquid-liquid microextraction (AALLME) coupled with graphite furnace atomic absorption spectrometry (GFAAS). In the proposed method, much less volume of an organic solvent was used as the extraction solvent in the absence of disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GFAAS. Several variables that could affect the extraction efficiency were investigated and optimized. Calibration graphs were linear in the range of 6.5-100 ng L-1. Detection limits for Co and Ni were 2.3 ng L-1 and 3 ng L-1, respectively. The accuracy of the developed procedure was checked by analyzing NRCC-SLRS4 Riverine water as a certified reference material. Finally, the proposed method has been successfully applied for the determination of cobalt (II) and nickel (II) ions in tap, surface and river water samples.

A reversed-phase salt assisted liquid-liquid extraction (RP-SALLE) method was developed for the preconcentration and determination of trace crocin in herbal medicines by high-performance liquid chromatography (HPLC). In developed method, the roles of the aqueous and organic phases are inverted so that the analyte is extracted from the organic into the aqueous phase after salt addition and phase separation. In this work, a mixture of methanol-acetonitrile (1:6 volume ratio) containing the extracted crocin from the powdered sample was used as the organic phase. Upon addition of sodium chloride to a mixture of methanol-acetonitrile-water and vortexing, crocin was enriched into the aqueous phase and sedimented at the bottom. A portion of the aqueous phase containing the analyte was then injected into the HPLC column for analysis. The RP-SALLE conditions including volume ratio of the solvents, pH of sample, salt concentration, time of vortex, type of salt and temperature as variable factors were carefully optimized. Under the optimized conditions, a linear calibration graph within 0.06 – 100 mg L-1 with an R2 exciding 0.999, a detection limit of 0.02 mg L-1 and a relative standard deviation of 3.5% for six replicates were obtained.

A selective, simple and low-cost method for the colorimetric determination of Fe3 ions based on chitosan capped silver nanoparticles (Chit-AgNPs) was presented. Chitosan is a cationic polyelectrolyte and possesses amino and hydroxy groups which make it widely used as a capping agent for Ag NPs. The synthesized chitosan capped silver nanoparticles with excellent colloidal stability were characterized by UV–Visible spectrometry, transmission electron microscopy, Fourier transform infrared, X-ray diffraction. Chit-AgNPs exhibit a strong surface plasmon resonance band which disappears in the presence of increasing concentrations of Fe3 ions. This system showed a visually detectable color change from brownish-yellow to colorless for the selective determination of Fe3. The method can be applied for the determination of Fe3 ions in the concentration range of 1.0×10-6 to 5.0×10-4 M. The detection limit was determined from three times the standard deviation of the blank signal (3σ/slope) as 5.3 × 10−7 M. The developed method was successfully applied for the determination of Fe3 real samples.

The present study describes the use of a new carbon paste electrode modified by means of Silica nanoparticles prepared by a simple and rapid procedure for the determination of sodium diclofenac (DCF). Moreover, the present study focuses on the characterization of electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) of the prepared Silica NPs-CPE. In this work, The electrochemical behavior of sodium diclofenac at the surface of Silica nanoparticles modified carbon paste electrode (Silica NPs-CPE) using current voltammetric methods (cyclic voltammetry (CV) and the differential pulse voltammetry (DPV) examined. The catalytic oxidation peak currents show a linear dependence on the diclofenac. Linear analytical curves were acquired in the ranges of 0.1 μM -500.0 μM and at the detection limit of 0.046 μM. Furthermore, the proposed modified electrode exhibited a high sensitivity, an excellent reproducibility, good selectivity, and a successfully easy construction process. The present study also examined the interferences of foreign substances. The method was used for the determination of sodium diclofenac present in real samples.

In this research, the magnetite polystyrene maleic anhydride (MPSMA) was synthesized and structure and morphology characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy techniques. The obtained nano-structured inorganic material was employed as a novel magnetic nanosorbent for separation and pre-concentration of Methyl violet (10B) dye from aqueous solutions, which can be spectrophotometrically monitored at λ = 585 nm after pre-concentration by solid phase extraction (SPE). The effect of several parameters including pH of the sample solution, amount of the sorbent, extraction and desorption times, and elution conditions and sample volume were investigated and optimized. UV–Vis spectrophotometer was used for determination of MV (10B) concentration after desorption of the dye by nitric acid solution. Under the optimum experimental conditions, the limit of detection and the relative standard deviation were 0.08 µg L–1 and 1.10 %, respectively. The enrichment factor of 200 was achieved and the calibration graph using the presented solid phase extraction system was linear in the range of 0.3 – 1500 µg L–1 with a correlation coefficient of 0.9989. The method was successfully applied to pre-concentration of MV (10B) from several textile waste water effluents.

It has been documented that specific follicular fluid (FF) biochemical characteristics may be essential to determining oocyte quality.
Lipid derivatives have most important role in the fertilization process and embryonic development. MALDI mass spectrometry is used for the diagnosis of biomolecules in the FF and serum of infertile women. FF and blood samples from 13 infertile women (20-38years old) undergoing intracytoplasmic sperm injection (ICSI) was obtained, stored frozen at -80º C, and later analyzed for Lipid Derivatives. Both FF and serum samples were compared and the Mfg was used as similarity index.
For comparison between the FF and serum samples for one person, the Mass spectrometry (MS) intensity ratio versus molecular weight, between the FF and serum samples were calculated. Out of 13 patients, three ongoing pregnancies were observed, so the percentage of pregnancy in the studied population was 25%.
The patients who became pregnant after micro-injection had higher unsaturated fatty acids and omega-3 fatty acid than other samples, but Stearic and Palmitic fatty acids were not high in these patients. A number of specific fatty esters and peptide derivatives in the FF and serum samples were found that may help to improve oocyte quality.

In this study, the novel surface ion-imprinted polymer (IIP) particles were prepared and applied as a electrode modifier in stripping voltammetric detection of lead(II) ion. A carbon paste electrode (CPE) modified with IIP nanoparticles and multi-walled carbon nanotubes (MWCNTs) was used for accumulation of toxic lead ions. Various factors that govern on electrochemical signals including carbon paste composition, pH of the preconcentration solution, supporting electrolyte, stirring time, reduction potential and time were studied in detail. The best electrochemical response for Pb(II) ions was obtained with a paste composition of 7% (w/w) of lead IIP, 10% MWCNTs, 53% (w/w) of graphite powder and 30% (w/w) of paraffin oil using a solution of 0.1 mol L-1 acetat buffer solution (pH=4.5) with a extraction time of 15 min. A sensitive response for Pb(II) ions in the concentration range of 3 to 55 µg L-1 was achived. The proposed electrochemical sensor showed low detection limit (0.5 µg L-1), remarkable selectivity and good reproducibility (RSD = 3.1%). Determination of lead(II) content in different environmental water samples was also realized adopting graphite furnace atomic absorptions spectrometry (GF-AAS) and the obtained results were satisfactory.

Surfactant-dye interactions are very important in chemical and dyeing processes. The dyes interact strongly with surfactant and show new spectrophotometric properties, so the UV-vis absorption spectrophotometric method has been used to study this process and extract some thermodynamic parameters. In this work, the association equilibrium between ionic dyes and ionic surfactant were studied by analyzing spectrophotometric data using chemometric methods. Methyl orange and crystal violet were selected as a model of cationic and anionic dyes respectively. Also sodium dodecyl sulphate and cetyltrimethylammonium bromide were selected as anionic and cationic surfactant, respectively. Hard model methods such as target transform fitting (TTF) classical multi-wavelength fitting and soft model method such as multivariate curve resolution (MCR) were used to analyze data that were recorded as a function of surfactant concentration in premicellar and postmicellar regions. Hard model methods were used to resolve data using ion-pair model in premicellar region in order to extract the concentration and spectral profiles of individual components and also related thermodynamic parameters. The equilibrium constants and other thermodynamic parameters of interaction of dyes with surfactants were determined by studying the dependence of their absorption spectra on the temperature in the range 293–308 K at concentrations of 5 × 10−6 M and 8 × 10−6 M for dye crystal violet and methyl orange, respectively. In postmicellar region, the MCR-ALS method was applied for resolving data and getting the spectra and concentration profiles in complex mixtures of dyes and surfactants.

The fact that oxidation, as one of the main routes of phase I metabolism of drugs, follows by conjugation reactions, and also formation of nitrenium ion as one of the clozapine oxidation products, directed us to investigate the oxidation of clozapine (CLZ) in the presence of nucleophile. The oxidation of clozapine (CLZ) has been studied on a glassy carbon electrode in the absence and presence of 2-thiobarbituric acid (TBA) as nucleophile in aqueous medium by means of cyclic voltammetry and on the graphite rods in controlled-potential coulometry. Cyclic voltammetry studies were realized for CLZ in the pHs 1.0 to 8.0. Results indicate that the electrochemical behavior of CLZ depends on the pH. Based on the obtained electrochemical results, an ECE mechanism was proposed to explain the electrochemical oxidation of CLZ. The results revealed that oxidized CLZ participates in Michael type addition reaction with TBA and via an EC mechanism converts to the corresponding new dibenzodiazepin derivatives. The product has been characterized by IR, 1H NMR, 13C NMR and MS.

The application of syringe to syringe dispersive liquid phase microextraction-solidified floating organic drop was extended for the separation and preconcentration of trace amounts of cadmium ions from water and cereal samples. The extracted cadmium was quantified by electrothermal atomic absorption spectrometry. Factors affecting the complex formation as well as microextraction efficiency such as the concentration of dithizone as the chelating agent, sample pH, type and volume of the extractant, number of injections, ionic strength and sample volume were optimized. Under optimized conditions, the calibration curve was linear in the range of 1.0-14.0 ng L-1 with the coefficient of determination of 0.9994. The limit of detection and quantification were found to be 0.25 and 0.85 ng L-1, respectively. The inter-day and intra-day precision at two concentration levels (3.0 and 10.0 ng L-1) were in the range of 3.9-9.2%. The accuracy of the developed method was evaluated through recovery experiments and the analysis of certified reference material (SLRS-6).

An ultrasensitive electrochemical immunosensor for the detection of tumor marker human chorionic gonadotropin (hCG) was developed with a limit of detection as low as 2 pg mL-1 in phosphate buffer. The Platinum nanoparticles (PtNPs) were electrodeposited to modify the gold surface and to increase enlarging the electrochemically active sites, resulting in the facilitation of electron exchange. Cysteamine (Cys) self-assembled monolayer was chemisorbed spontaneously on Pt substrates via the Pt-S bond and the amine groups array exposed on the electrode surface was used to anchor AgNPs through electrostatic interaction. AgNPs increased the immobilized amount of antibodies on the electrode to enhance the sensitivity of the sensor. Under optimal experimental parameters, Differential pulse voltammetry (DPV) signal changes of the [Fe(CN)6]3-/4- are used to detect hCG with two broad linear ranges: 0.007 to 1.11 and 1.11 to 68 ng mL-1. The reported strategy has provided a promising platform for highly sensitive and selective detection of hCG. Finally, the proposed immunosensor is successfully used in detecting hCG in a human serum samples.