Analytical and Bioanalytical Chemistry Research
Volume:9 Issue: 3, Summer 2022

Nickel ions are toxic to the environment and they are also relevant in biology. Fluorescence sensing is a sensitive method and metal sensing can be carried out employing cheaper and easy-to-synthesize molecules that possess fluorescence emission. Therefore, development of newer and simply-synthesized chemosensor molecules for nickel ions in aqueous medium are required. We report, in this paper, a simple semicarbazone derivative of a piperidin-4-one as a nickel ion sensor in water. The compound forms a 1:1 stoichiometric complex with nickel ions. The association constant value is 4.04 × 104 mol-1 dm3. The nickel ion-selectivity of the compound is explored emploting UV-vis and fluorescence spectroscopy. Ni2+ ion-chelation enhances the fluorescence of the chemosensor molecule. The Ni2+ detection limit of the chemosensor was 1 × 10-7 mol dm-3. The compound also forms a 1:2 inclusion complex with β-cyclodextrin. The structure of the complex is proposed. Host : guest complex formation of β-cyclodextrin with the piperidin-4-one derivative results in the interference of the host molecule with the chelation of Ni2+ ions. As an extension of the application of the piperidin-4-one derivative, we demonstrate the Ni(II) ion filtration by incorporating the compound with a polysulfone film.

The present study deals with the simultaneous determination of Co (II) and Fe (II) ions using derivative spectroscopy after pre-concentration by surface-active ionic liquid-assisted cloud point extraction. Wider linear range, less detection limit and more reproducibility along with the improved extraction efficiency highlight the advantages of the proposed method compared to the conventional CPE method. On the other hand, in comparison to the hydrophilic ionic liquids, a more effective and efficient extraction medium is provided due to the formation of homogeneously dispersed micro-droplets of surface-active ionic liquid (SAIL) micelles. Some important variables affecting the extraction efficiency such as sample pH, the concentration of SAIL 1-hexadecyl-3-methylimidazolium chloride (C16MeImCl), the volume of Triton X-114, the concentration of the chelating agent, the concentration of NaCl, centrifugation conditions, equilibrium temperature and time were optimized. Under the selected optimized conditions, the resulting calibration graph obtained by derivative spectroscopy was linear in the range of 0.15 to 2.0 mg L-1 for cobalt and 0.05 to 0.75 mg L-1 for iron at zero-crossing wavelengths of 598 and 567 nm, respectively. The detection limits achieved were 0.07 mg L-1 for cobalt and 0.01 mg L-1 for iron ions. The relative standard deviation in all cases was less than 4%. The proposed method was successfully applied to the simultaneous determination of cobalt and iron ions in various real samples.

Cloud Point Extraction (CPE) is an economic, rapid, and environmentally friendly method. It was performed by preconcentration samples (water and soil) that contained palladium. An ion-pair association complex was formed when the chromogenic reagent 2-(4-hydroxy phenyl azo)-4-benzene naphthol (HPBN) reacted with palladium in HCl media. It was then extracted into a surfactant (Triton X-114) rich phase. After diluting the cloud point layer with acidic methanol, the concentration of enriched samples was determined by UV-Vis spectroscopy. The effects of Triton X-114 and HCl concentra-tions, heating time, temperature, centrifuge rate, incubation duration, and interferences on cloud point extraction were analyzed and improved. The short extraction time (8 minutes) is an advantage of this method. The limit of detection (LOD) and the limit of quantification (LOQ) are low (0.10 and 0.30 μg L-1, respectively). The enrichment fac-tor (EF) and preconcentration factor (PF) are calculated to be 40 and 100, respectively. The precision for the approach was determined to be (RSD 1.10%, n = 6). For collect-ed samples, the FAAS was used to assess the accuracy of the modified preconcentra-tion technique. The method can be used to detect palladium in natural samples, with relative recovery values ranging from 93 to 109% for various concentrations, demon-strating its accuracy.

A selective and sensitive voltammetric sensor was constructed using a Poly(methyl orange)/glassy carbon electrode (PMO/GCE). The PMO/GCE sensor was applied to investigate the electrochemical behavior of ascorbic acid (AA) and vitamin B2 (VB2) in PBS buffer solution. The sensor was applied for individual and simultaneous determination of AA and VB2using cyclic and differential pulse voltammetry (DPV) techniques. Different experimental parameters including scan rate(25-500 mV/s), pH (4-8 for AA and 3-10 for VB2) and analyte concentration (10-40 µM for AA and 4-85 µM for VB2) have been studied and optimized. High electrocatalytic activities for AA and VB2 oxidation were achieved at pH 7.0 and 6.0, respectively. In addition, results denoted that the oxidation process of AA and VB2 was under diffusion control. The respective detection limits, quantitation limits and linear ranges were 0.575, 1.916 and 10-40 μM for AA and 0.922, 3.073 and 5-85 μM for VB2under the optimized DPV conditions. Peak separation of AA from VB2was 660 mV which is enough to determine these vitamins simultaneously. The fabricated sensor has been applied successfully for estimation of AA and VB2 in real samples with good selectivity, stability and reproducibility.

The quantitative results in the pesticide residue analysis by gas chromatography-mass spectrometry are adversely affected by the phenomenon known as the matrix effects. A matrix effect may be noticed as an increase or decrease in the response of the detector signal compared with the response produced by solvent solutions of the analytes. The purpose of this research is to evaluate and compare the matrix effects in two nutraceutical samples (Alpa and Alpa Lesana), containing alcohol and herbal extracts. Samples were extracted by dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry analysis. Thirty-eight pesticides from different chemical classes were used to evaluate the matrix effects. Matrix effects were studied by calculating the matrix factor for each pesticide for the two herbal-based potions. The method was validated in terms of trueness (recoveries 70 % - 120 %), precision (below 20 %), linearity (correlation coefficients for Alpa higher than 0.98; for Alpa Lesana in the range of 0.83 to 0.99), and the limits of detection (0.001 µg/L - 0.780 µg/L (Alpa); 0.014 µg/L - 0.812 µg/L for Alpa Lesana). The present study revealed the strong dependence of matrix effects on the sample type and the complexity of the matrix. Most of the pesticides showed strong signal enhancement in the case of Alpa Lesana analysis. On the other hand, most of the pesticides were influenced only minimally in the case of Alpa analysis. To compensate the matrix effects, the utilization matrix match standard solutions for calibration is recommended for both samples.

Metoprolol (MTP), a selective beta-blocker with low biodegradability, is an important micro-pollutant that has been widely identified in surface waters and wastewaters. In this work, the removal of MTP from aqueous solutions was performed using Iron oxide/Titanium oxide/activated carbon (Fe3O4/TiO2/AC) nanocomposite as a new adsorbent. The nanocomposite was characterized by Fourier Transform Infrared (FT-IR), Energy Dispersive X-ray Spectroscopy (EDX), Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Diffraction (XRD) techniques. The maximum efficiency of MTP removal was 96.2% at a dosage of 1.5 g l-1 of adsorbent, an initial concentration of 10 mg l-1 of the drug, a contact time of 60 min at 25 °C, and pH 8.0. Freundlich and Pseudo-second-order models were found to be the best fitting isotherm and kinetic models, respectively. In addition, the values of thermodynamic parameters including ΔH, ΔS, and ΔG were found to be -75.20, -0.23, and -7.55 kJ mol-1, respectively. These results confirmed that the adsorption process of MTP on Fe3O4/TiO2/AC is exothermic and spontaneous. Fe3O4/TiO2/AC nanocomposite was successfully used for the removal of MTP from real water solutions.

This work reports preparation of a graphitized mesoporous carbon and a phytochemical; piperine based electro-active composite. The composite was chemically modified over a glassy carbon electrode, designated as GCE/GMC@pp. The GCE/GMC@pp exhibited a highly stable redox peak at E1/2 =0.2 V vs. Ag/AgCl in pH 7 phosphate buffer solution (PBS). Further, the prepared electrode gave exceptionally selective response towards Hydrazine (HyD) sensing at E0=0.235 V vs Ag/AgCl . In addition, the sensor gave a linear response towards the changing HyD concentration from 10µM-90µM with the limit of detection as 120 nM. To explore the practical applicability, effect of interference with co-existing analytes like H2O2, Pb+2, Cd+2, NO2-3, NO2-2, Cr(II), Arsenic (Ars) were studied and an interference mitigated response was observed. Finally, a real sample of tap water was tested and an appreciable recovery values were obtained. Overall, the prepared composite exhibited excellent electro-catalytic activity towards HyD and has great a potential for the real time trace HyD detection.

A novel modified glassy carbon electrode (GCE) was successfully fabricated with 1-(E)-4-((2-(2,4-dinitrophenyl)hydrazono)methyl)benzene-1,2-diol (DDH) and reduced graphene oxide-ytterbium nanoparticles (rGO-Yb2O3 NP) for the determination of metoclopramide (MC). The electrochemical behavior of the modified electrode (rGO-Yb2O3-DDH/GCE) was investigated by common and practical methods including differential pulse voltammetry, chronoamperometry and cyclic voltammetry. It was found that the rGO-Yb2O3-DDH composite has a coherent electrocatalytic role in the oxidation of metoclopramide with relatively high stability, lifetime and sensitivity. The characterization of the nanocomposite was done by X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The MC oxidation took place at the optimum pH of 7.0 and a potential that was about 810 mV more negative than that of an unmodified glassy carbon electrode. Under optimized conditions, the corresponding linear calibration curves were found to be in the linear dynamic range of 25.0-3000.0 µM with the detection limit of 7.14 µM. Finally, the proposed electrode was successfully used to measure MC in blood serum samples.