Analytical and Bioanalytical Chemistry Research
Volume:10 Issue: 4, Autumn 2023

The present study aims to introduce a highly sensitive electrochemical sensor for quantification of trace amounts of Sumatriptan (SUM) in biological fluids. To immobilize a stable nano film of β-cyclodextrin (β-CD) on a glassy carbon electrode (GCE), electropolymerization of monomer was carried out within 0.1 M phosphate buffer with pH 6.0 utilizing cyclic voltammetry to yield polymerized β-CD (pβ-CD). The morphological characterization of pβ-CD/GCE was examined by Field emission scanning electron microscopy (FESEM). The electrochemical redox action of SUM on pβ-CD/GCE was scrutiny studied by cyclic voltammetry and chronocoulometry. The electrochemical parameters including the electron transfer coefficient (α), the standard heterogeneous rate constant (ks), the surface area of the electrode (A), the electron transfer number (n), and the surface coverage (Γ) were estimated to be 0.38, 1.23×10-3 cm s-1, 0.06 cm2, 1, 1.07×10-8 mol cm-2, respectively. At optimized criteria, a substantial enhancement was attained toward the electrooxidation of SUM on the developed electrode compared to the bare GCE, resulting in wide linear ranges of 0.0622.47µM and 2.4752.1µM with a low detection limit of 27 nM. The developed sensor was successfully employed for quantification of SUM in human blood serum and urine samples with good selectivity and acceptable recoveries, proving its utility for further applications as a sensitive and reliable sensor.

The electrochemical behavior of epinephrine (EP) at the catechol modified glassy carbon electrode (catechol/GCE) in phosphate buffer solution (PBS, pH = 7.0) was examined using cyclic voltammetry (CV), chronoamperometry (CA) and differential pulse voltammetry (DPV). The results of electrochemical studies confirmed the ability of catechol to accelerate the electron transfer process and reduce overvoltage for the oxidation of EP. DPV studies showed two dynamic ranges, of which in the low concentration range of EP, the detection limit was reported to be 1.6 µM. Moreover, the reproducibility, repeatability and selectivity of the designed sensor were investigated using DPV method. The selectivity of this sensor was studied in the presence of interfering substances such as glucose, fructose, ascorbic acid, sodium chloride, potassium chloride, norepinephrine and dopamine. Catechol/GCE was used for quantitative measurements of EP in human blood serum sample. DPV studies reported two linear segments with slopes of 0.0186 and 0.0068 µA µM-1 in the concentration ranges of 5.0-80.0 and 100.0-900.0 µM, respectively. The detection limit (3Sb/m) and sensitivity for the low concentration range of EP were found to be 1.61 µM and 0.6 µA µM-1 cm-2, respectively.

Quantitative determination of clindamycin by UV spectrophotometry is limited due to lack of UV chromophore of clindamycin structure. In this study, UV spectrophotometry employing partial least square regression (PLSR) model was developed with respect to high-performance liquid chromatography (HPLC) as the reference method for the quantitative determination of clindamycin phosphate in gel preparation. The successful PLSR model used UV spectral data in the region of 190  400 nm without data preprocessing. The leave-one-out cross- validation was utilized for model construction. The latent factor 2 was used in the final model with the R2 model of 0.9972, root mean square error of calibration (RMSEC) and root mean square error of cross-validation (RMSECV) of 0.0044 and 0.0048, respectively. Model ability was approved by quantitative determination of 20 validation samples that were not contributed in the model building step. Accuracy of determination results expressed in terms of root mean square error of prediction (RMSEP), the relative standard error of prediction (RSEP%) and bias were 0.0072, 0.0447% and -0.0025, respectively. This study demonstrated that PLSR assisted-UV spectrophotometry could be used as an alternative method for the quantitative determination of non-UV chromophore active pharmaceutical ingredients in the pharmaceutical dosage form.

A variety of influences can cause DNA damage to the genome. The hydroxyl radical attacks the C-8 atom of guanine, forming 8-hydroxyguanine (8-OHGua) or 8-hydroxy-2ˈ-deoxyguanosine (8-OH-2'dG) which are an important indicator of oxidative damage on DNA. Determining these damaged base products can be accomplished through measurement by LC-MS/MS after enzymatic hydrolysis or measurement by GC-MS/MS after chemical hydrolysis. In this study, it was aimed to hydrolyze DNA using various strong acids and to measure 8-hydroxyguanine by LC-MS/MS. In the first stage of the study, the nucleoside 8-hydroxy-2'-deoxyguanosine was treated with HCl (2 M and 6 M), TCA (10%), TFA (10%), o-phosphoric acid (2 M), methanesulfonic acid (2 M), and formic acid (80%). The amounts of 8-hydroxyguanine were determined by LC-MS/MS. It has been identified that formic acid with the highest yield (70%) hydrolyzes the β-glycosidic linkage between the base and the sugar. Subsequently, oxidative damage was induced on calf thymus DNA by producing hydroxyl radicals via Fenton reaction. The resulting oxidative damaged DNA, was hydrolyzed using formic acid. The amount of 8-hydroxyguanine was then determined using by LC-MS/MS. Based on the results obtained, it was observed that the acidic hydrolysis applied was effective in breaking the N-glycosidic bond, but not effective in breaking the phosphodiester bond of oxidatively damaged DNA.

Three dimensional (3D) and two dimensional (2D) quantitative structure–property relationship (QSPR) models were established to computer-aided design of new phosphorus-containing podands extractants of the uranyl cation. GRIND methodology, where descriptors are derived from GRID molecular interaction fields (MIF), and Dragon generated descriptors were used to perform QSPR modelling of the distribution coefficient (log D). The best model for 3D-QSPR has been obtained with R2=0.93 and Q2 =0.79. Some simple 2D-QSPR models, able to correlate and predict the log D are developed. The final models satisfied a set of rigorous validation criteria and performed well in the prediction of an external test set. The results reveal the role of size and steric hindrance of hydrophobic part of extractant molecule, as well as the importance of electrostatics and charge transfer interactions in distribution coefficient of uranyl cation. This information could be very useful to design the most efficient ligands and find new extractants for uranyl ion extraction.

Extraction of ammonia compounds from food samples is a challenging topic due to the hydrophilic property of ammonia. A simple and rapid extraction method was developed for the determination of ammonia in a type of local bread (Ahari bread) and milk samples using a salting-out assisted liquid-liquid extraction and spectrophotometry. Acetonitrile was used to clean up, and potassium chloride salt solution was added to separate the acetonitrile and aqueous phase by creating two phases. The ammonia concentration in the aqueous phase was determined based on a colorimetric method. Various parameters affecting absorption intensity were optimized using the response surface methodology. Then, the optimized parameters were applied to establish a valid analytical method. The developed method was used to quantify ammonia compounds in food samples, i.e. Ahari bread and milk, by the standard addition method. The linearity of the method was from 2.5 to 40 μg/mL with a coefficient of determination (R2) of 0.994, and numerical values of a limit of detection (LOD), and limit of quantification (LOQ) was found to be 0.038 and 1.29 μg/mL, respectively. The accuracy (%error) and precision (%relative standard deviation) were in the acceptable range. The established extraction technique and standard addition method could detect ammonia in real food samples. These data showed that the established analysis approach is a simple and sensitive technique for extraction and determination of ammonia concentration in foodstuff.

A new selective molecular imprinted polymer (MIP) was synthesized for electrochemical sensing of aminophylline (AMI). The MIP was fabricated via the co-polymerization of different monomers (acrylamide and methacrylic acid) around the template (AMI) in the presence of a cross-linker (ethylene glycol dimethacrylate) and an initiator (potassium persulfate). The prepared polymers were characterized by CHN elemental analysis, Fourier-transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy. For electrochemical applications, a voltammetric sensor was constructed by dropping MIP on the glassy carbon electrode surface after modification with the graphene oxide. Electrochemical determinations were achieved using differential pulse voltammetry (DPV), which indicated a wide range (3.7×10-11- 1×10-3 mol L-1) of AMI and a low detection limit (2.1×10-12 mol L-1). Alternatively, MIP was immobilized on a plasticized PVC membrane and deposited as one layer on the GCE to fabricate the potentiometric sensor. In the same context, a potentiometric sensor was constructed and exhibited a linear calibration curve in the concentration range of 2.6×10-9 mol L-1 to 3.1×10-3 mol L-1, with a detection limit of 1.5×10-10 mol L-1. Additionally, the developed methods displayed great selectivity for AMI compared to other competing molecules, high repeatability, and stability. In addition, the proposed methods were successfully applied for AMI detection in pharmaceutical drugs with recovery values (98.2 - 99.6%).

A facile and efficient stir bar sorptive extraction method was developed for the extraction of four antiparasitic drugs including eprinomectin, doramectin, ivermectin, and abamectin from cow milk samples. The extracted analytes were determined by high performance liquid chromatography-diode array detector. In this work, firstly, milk sample was deproteinized and the obtained clear solution was extracted by a stir bar coated with octadecylsilane (as the sorbent). After extraction, the adsorbed analytes onto the sorbent surface were eluted by a proper volume of 1-butyl-3-methylimidazolium tetrafluoroborate as ionic liquid. All of the effective parameters including sorbent type and amount, elution solvent type and volume, stirring time, deproteinization agent solution volume and concentration were investigated by design of expert using response surface methodology. Under optimal conditions, acceptable extraction recoveries (68 to 83%) and enrichment factors (72 to 88), low limits of determination (0.05 to 0.12 ng/mL) and quantification (0.17–0.41 ng/mL) were obtained. The method precision was evaluated by analyzing the spiked samples using the introduced method in a day and different days. The obtained relative standard deviations were in the ranges of 2.3-4.1 and 2.8-4.9%, for intra- and inter-days repeatability, respectively. At last, the presence of studied drugs in milk samples was followed and ivermectin was found in some samples. The literature review verified that the method was not performed previously and can be utilized as a routine method for analyzing antiparasitic drugs.

A novel, repeatable, and swift kinetic approach for determining alpha-lipoic acid (ALA) in sodium lauryl sulfate (SLS) micellar medium has been presented, and it has been connected to ALA determination in drug formulations. The approach is based on ALA inhibitory property. ALA (containing two sulfur atoms) forms a chelate with Hg2+, lowering the effective [Hg(II)], and ultimately, the Hg2+ catalyzed cyanide substitution rate from [Ru(CN)6]4- by nitroso-R-salt (N-R-salt). Fixed times of 5 and 10 minutes were chosen under optimal reaction conditions with [N-R-salt] = 0.45 mM, pH = 7.0 ± 0.02, Temp = 45 ± 0.2 °C, I = 0.1 M (NaClO4), [Ru(CN)64-] = 42.5 µM, [Hg+2] = 0.25 mM, and [SLS] = 8.5 mM to calculate the absorbance at 525 nm associated with the final substitution product [Ru(CN)5 N-R-salt]3-. ALA's inhibiting influence on the Hg2+ catalyzed cyanide substitution with N-R-salt from [Ru(CN)6]4-, has been represented by a modified mechanistic approach. The concentration of ALA in various water specimens can be measured at the micro-level down to 2.5 µM using the established kinetic spectrophotometric approach. The suggested method is highly reproducible and has been effectively applied to accurately quantify the ALA in pharmaceutical samples. Even as much as 1000 with [ALA], Excipients used in medications do not significantly hinder the determination of ALA.

Staphylococcus Aureus is an extremely dangerous infectious pathogen in the healthcare and community setting. Discovery of the right chemotherapies to treat this infection has been difficult due to the high toxicity associated with some of the most effective drugs. Computational chemistry is helping to identify potential effective drugs to treat this infection. In this study molecular docking was utilized to examine the effects of 3 different compounds on Staphylococcus aureus and HTH3E. The structure of the ligands was drawn in Chemdraw software and the molecular docking was carried out using Pyrx computational tool. Visualizations of the docking interactions with the target active site were generated via Discovery Studio. HTH3E showed the lowest binding affinity with a score of -27.105 kcal/mol. The results demonstrate that (3-amino-5-hydroxy-2-methyl-1H-pyrrol-1-yl)(5-hydroxy-1H-1λ6-thiophen-3-yl)methyl carbamic acid is a promising lead and therefore further study of this compound is warranted. The newly designed compound was also subjected to molecular dynamics study and was found to be stable and firmly fixed in the binding pocket of the receptor.