Analytical and Bioanalytical Chemistry Research
Volume:9 Issue: 4, Autumn 2022

In recent years, oligonucleotide libraries have been used to screen for high-affinity and high-selectivity aptamers that target proteins, peptides, small molecules, or cells. The members of a traditional oligonucleotide library contain a randomized central region with a single-stranded primer region at each end for amplifying target-bound central sequences. However, the single-stranded primers may interact with complementary sequences in the central region of the oligonucleotide and interfere with target-binding. The authors proposed a new library design that uses self-folded motifs to replace the single-stranded primers. For proof of concept, highly structured intercalated motifs (i-motifs) were used to construct the primer regions, and DNA oligonucleotides containing a known streptavidin-binding aptamer in the central region were used to evaluate the performance of the i-motif primers. The applicability of i-motif primers for polymerase chain reaction (PCR) was evaluated as well. The experimental results indicate that the self-folded i-motif primers do not interrupt streptavidin binding to the central region of the DNA oligonucleotide, and that they are PCR-friendly. Finally, when these self-folding primers were used to construct the members of an otherwise traditional DNA library, the target molecules were successfully collected, demonstrating that such primers are a viable alternative to the traditional single-stranded primers in the members of an oligonucleotide library used for aptamer screening.

The proposed analytical method tries to illustrate a new approach for the extraction of some pesticides from different fruit beverages (orange, pineapple, cherry, and mango) using UiO-66 as a capable adsorbent. Further preconcentration for heightening enrichment factors of the analytes was accomplished using a dispersive liquid-liquid microextraction. The synthesized adsorbent was carefully characterized using nitrogen adsorption/desorption, X-ray diffraction, MAP, Fourier transform infrared spectrophotometry, energy dispersive X-ray, and scanning electron microscopy analyses. The performed analyses proved the successful formation of the desired compound. After the sorption of the target compounds onto UiO-66 particles by vortexing, the adsorbent was separated by centrifugation. The analyte-loaded adsorbent was treated with 1.0 mL of acetonitrile for the aim of desorption. The obtained eluate containing the desorbed pesticides was mixed with 38 µL of 1,1,1-trichloroethane and hastily injected into sodium chloride solution. After the centrifugation, an aliquot of the sedimented phase was injected into a gas chromatograph equipped with a flame ionization detector. Satisfactory figures of merit obtained in this survey consisted of high enrichment factors (215-275), acceptable extraction recoveries (43-55%), low limits of detection (1.10-2.35 µg L-1) and quantification (3.66-7.82 µg L-1), low relative standard deviations (≤ 7.8%), and wide linear ranges. Also, the proposed method benefits from the high surface area of the adsorbent and low matrix effect.

In this study, anticonvulsant activity of phenylacetanilides compounds was predicted using QSAR and artificial neural network (ANN) models. Variety kinds of molecular descriptors were computed using Dragon for 30 monosubstituted phenylacetanilides. Then, seven out of 1600 descriptors were selected and used in ANN analysis. The complete set of 30 compounds was randomly divided into a training set of 80%, a test set of 10%, and a validation set of 10% compounds. Moreover, multiple linear regression (MLR) analysis was utilized to build a linear model by using the same descriptors and the results of this linear model were compared with the nonlinear ANN analysis. The obtained Correlation coefficient (R2) and mean squared error (MSE) of the ANN and MLR models (for the whole dataset) were 0.85, 0.06816; and 0.6, 0.09792, respectively. The higher R2 of ANN method revealed that the relationship between the descriptors and anticonvulsant activity of the compounds is non-linear.

Astaxanthin is a carotenoid produced by different microalgaes, bacterias, and yeasts in fish samples. Some fishes like salmon contains astaxanthin in their muscles and it can be a proper indicator for identification of fishes. In this work, a simple and validated ultrasonic-assisted liquid-liquid extraction coupled to high performance liquid chromatography-ultraviolet detector was developed for determination of astaxanthin in fish samples in order to identify the trout from colored salmon sold in Iranian fish markets. Under the optimum conditions, analytical features of the method including limit of detection (1.46 ng/g) and quantification (5.46 ng/g), linearity (r2=0.995), precision (RSD≤5.2%), accuracy (RSD≤8%), and recovery (90%) were acceptable. The method was successfully used to determine the target analyte in several fish samples including thirty salmon produced in Iran, five salmon produced in Norway, and five trout samples. The results showed that trout samples were free of astaxanthin, while salmon samples produced in Iran have astaxanthin in the range of 179 ± 9 - 782 ± 40 ng/g. The content of astaxanthin in Norwegian salmons is much higher than salmon samples produced in Iran.

The novel application of interval variable iterative space shrinkage approach iVISSA and partial least squares PLS calibration for quantification of three overlapping pharmaceuticals (Paracetamol, Guaifenesin, and Phenylephrine) is presented in this work. In addition to spectral overlapping, the drugs are available in the commercial tablet in varying proportions where Paracetamol and Guaifenesin are 20 to 50 times higher than Phenylephrine. Net analyte signal calculations indicated that pH has an high influence on drug overlapping, and the optimum pH was at 12.0, with a total overlapping 57-77% among solutes. To eliminate the influence of excipients on PLS calibration, all standard mixtures were prepared in a 5% level of excipients. iVISSA resulted in the excellent prediction of Phenylephrine by selecting 34 spectral data in which the solute was intensely absorbed. Analysis of commercial tablet (250 mg Paracetamol, 100 mg Guaifenesin, 5 mg Phenylephrine) with the help of NAS revealed that GUA was predicted with high accuracy (98.4%) and precision (RSD 3.9) using the range 225-239 nm. For Phenylephrine, the selected intervals were 200-207, 224-225, 232-246, 250-254, 263, 267-270, 275, and 278-280 nm by iVISSA, which resulted in accurate quantification with high accuracy (104.3%) and precision (RSD 0.5). For Paracetamol, including the entire range (200-300 nm, 101 points) was necessary for better PLS prediction while variables selection by NAS or iVISSA negatively affected PLS calibration for that drug. The accuracy and precision of the proposed method were validated against liquid chromatography and both methods were found statically comparable.

A simple, rapid, and efficient vortex-assisted liquid-liquid microextraction procedure was proposed for the extraction and preconcentration of Hg(II) ions at trace levels in aqueous samples prior to its indirect determination by flame atomic absorption spectrometry. In this study, at first, zinc ditizonate was formed in aqueous solution and then extracted into carbon tetrachloride. Then it was added to sample solution at µL-level and the obtained mixture was vortexed. In this step, Zn(II) in zinc ditizonate was replaced by Hg(II) of aqueous phase and concentration of Zn(II) in organic phase was reduced. After centrifuging, carbon tetrachloride containing dithizonate complexes of Zn(II) and Hg(II) was sedimented. To determine the amount of Hg(II) in the sample solution, the sedimented phase was injected into the instrument and concentration of the remained Zn(II) was determined. Finally, Hg(II) concentration was determined by the difference of the obtained absorbance and the absorbance of a blank (Hg(II)-free aqueous phase extracted by the above-mentioned procedure). Under the optimum experimental conditions, the linear range was obtained in the range of 0.25-15 µg L−1. The relative standard deviations (n=6) for the concentrations of 1 and 5 µg L−1 were obtained 5.2 and 3.3%, respectively. Moreover, the obtained detection and quantification limits were 0.04 and 0.10 µg L−1, respectively. Finally, the suggested extraction method was successfully used for the extraction of Hg(II) ions in real water samples.

Ionic associates of basic fuchsin have been used as electrochemical sensing probe for the potentiometric determination of 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chlorophenoxyacetic acid (4-CPA). Influence of the membrane composition on electroanalytical characteristics of the electrodes has been established. Effect of the modifying additive (N,N,N',N'-tetramethylethylenediamine) on the chemical and analytical characteristics of the electrodes is shown. The sensors can be used for the determination of 2,4-D (4-CPA) in an analytical range of 1×10-4 to 3×10-2 M with LOD as 10-5 M. For 2,4-D ISE, a hyper-Nernstian function was observed. The sensors have been applied for the determination of 4-CPA and 2,4-D in model solutions of pesticide preparations.The ion-selective electrode may be efficiently used in either model or real samples, providing a low detection limit detection; The electrode may be made more efficient, if the lypophylic basic additive is used for electrode production. Its addition has significant importance for the electrode response.

In this study, nickel elimination per kaolin from Guelma/Algeria in aqueous medium was examined by applying several parameters, namely the agitation speed, pH, temperature, particle size of the solid and initial concentration. The physico-chemical investigations accomplished indicated that the kaolin in majority is composed of silica (46.58%) and alumina (36.82). The measured specific surfaces of the raw and activated kaolin samples are respectively 98m2/g and 310m2/g. The pH value corresponding to the PZC is around 3.1. The adsorption capacity is measured after 60 minutes of stirring under specific conditions, namely Vag: 150 rpm; pH: 4.3; T: 20°C; Øs: 200µm corresponds to 45.39 mg/g. The study of the adsorption isotherms demonstrated that the Langmuir model was better adapted to the experimental data than the Freundlich and Temkin models. The values of the Langmuir parameter RL, showed that the nickel adsorption process is favourable. The kinetic study has revealed that kinetics follows the pseudo-first-order model. However, a diffusion study has indicated that the transfer of nickel from the solution to the adsorbent was successfully controlled by external and intra-particle diffusion. The effect of temperature has indicated that this adsorption is physical, spontaneous (ΔG°<0), exothermic (ΔH°<0) and less entropic (ΔS°<0). The nickel desorption from charged kaolin is more efficient using hydrochloric acid at 0.1N as eluent. Considering of the determined results, we estimate that kaolin from Guelma / Algeria, can be valued as a reliable, efficient and economical adsorbent for the elimination of nickel from wastewater.

Narcotic drug use is an important problem in our country and all over the world. Hair is a valuable specimen for monitoring these long-term drug uses. For this purpose, a sensitive method was created and validated for the identification and quantification of benzoylecgonine (, morphine, codeine, 6-monoacetylmorphine, heroin, tetrahydrocannabinol, amphetamine, 3,4-methylenedioxyamphetamine, buprenorphine, methamphetamine, 3,4-methylenedioxy-N-methylamphetamine, and cocaine in human hair by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The sample preparation step includes washing, standard addition, liquid-phase extraction with methanol, and solid-phase extraction steps. Analysis for substances identified from a pretreated hair took a maximum of 3.64 minutes. In the method, the LOD values of each substance ranged from 0.11-0.87 ng/mg, and the linearity was quite good (r2>0.99). The concentration ranges for quantification were 0.50 and 8.00ng/mg for all substances. In addition, the intraday and interday accuracy and precision values of this method were acceptable (˂12.81%) and the recovery was found to be between 93.72%-104.78% at different concentrations. The results of this study showed that the developed very fast and reliable LC-MS/MS method is suitable for use as a validated method in the analysis of illicit drugs simultaneously in hair.

The glassy carbon electrode (GCE) was modified with sunset yellow (SY) food dye to develop a simple, environmentally friendly, low-cost electrochemical sensor. The electrode performance as a useful sensor was demonstrated in the simultaneous and selective measurement of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The SY dye was covalently fixed on the electrode surface. The structure and morphology of the modified electrode were investigated by scanning electron microscopy (SEM), and the results showed that SY particles were located on the surface of the GC electrode. The electrochemical activity of the modified electrode was measured using cyclic voltammetry (CV), chronoamperometry, chronocoulometry, and impedance spectroscopy (EIS) techniques. The results showed that under optimal conditions, the SY/NaOH-treated-GCE has good electrocatalytic activity, a suitable linear range (7-320, 0.2-45, 0.2-50 µM), low detection limit (4.78, 0.12, 0.12 µM) for AA, DA, and UA respectively, and high stability. Analytical application of SY/NaOH-treated-GCE was successfully evaluated to determine AA, DA, and UA in bell pepper, grapefruit, dopamine ampoule, vitamin C tablet, tap water, and biological samples ( human blood and urine ). The results obtained by our team show that the SY/NaOH-Treated-GCE is suitable for simultaneous and selective measurement of electroactive species in various biologic and pharmaceutical samples.

Sports and weight control supplements are tempting targets for adulteration. Amphetamines have been mainly prescribed as weight-loss drugs in the past decades. Amphetamines are also abused by athletes to improve their performance. To ensure the content of sports supplements, we propose a simple and straightforward magnetic dispersive solid-phase extraction method to extract amphetamine (AM) and methamphetamine (MET) from sports supplements. A few milligrams of magnetic graphene oxide (GO@Fe3O4) were added to the sample solution for microextraction assisted by shaking. Due to the benefit of dispersion and the high mass transfer rate of the sub-microscale adsorbent, the extraction equilibrium was achieved in a very short time (3 min). Moreover, thanks to the magnetic properties of adsorbent, the separation of the adsorbent from sample solution was easily achieved by an external magnetic field, which therefore simplified the sample pretreatment procedure. A high-performance liquid chromatography-ultraviolet (HPLC-UV) method with precision and accuracy better than 10% was proposed to detect AM and MET in the range of 300-1500 ng/mL and 500-2000 ng/mL, respectively. As a confirmatory analysis of determined AM and MET, an ion-spray LC-MS/MS method using multiple reaction monitoring (MRM) mode was applied. The LC-MS/MS method was linear in the range of 5-100 ng/mL and 1-200 ng/mL for AM and MET, respectively. Sixteen sports supplements; were scanned using the proposed method and AM and MET were confirmed in four out of sixteen samples.

In this study, the researcher has focused on manufacturing a new, highly selective, and simple optical membrane for the determination of cobalt (II) ions in aqueous solutions. The cobalt (II) is first oxidized when using hydrogen peroxide (H2O2) solution, to eliminate the effect of the concomitant species and increase the selectivity in the determination of cobalt (II) in real samples. The obtained cobalt (III) ions were determined through recording the absorbance intensity of the new selective and sensitive thin optically transparent sensor. 1-nitroso-2-naphthol (1N2N) is used as a sensitive, selective and stable complexing ligand to change the absorbance of the transparent membrane into the presence of cobalt (III). The ready-made optical sensor indicated a good reproducibility and a relatively long lifetime and stability with an appropriate linear response from 0.1 to 5.0 mg L-1. The limit of detection was obtained 0.03 mg L-1. Further investigations were evaluated in an intra-day and inter-day precision (RSD %) 2.76-4.46% and 0.89-5.39%, one after another, and the average percentage of relative error (RE %), was in the range of 1.89 to 3.41. The results indicated that the utilized method could successfully determine cobalt (II) in different water samples containing tap water, seawater and spring water, without any pretreatment.