Current Analytical Chemistry - Volume 19, Issue 8, 2023

The need for toxicological screening of amphetamine users is growing in parallel with its increasing abuse. At the same time, it turns out that these substances most often give false results in rapid drug immunoassay. Therefore, the aim of the present work was to investigate the sources of false positive or false negative results. For this purpose, an analysis of the literature sources in the databases of Google Scholar, PubMed, and Science Direct, was made. The results showed that a number of prescription or OTC medications can cause false positive results due to cross-reactivity (ephedrine, pseudoephedrine, labetalol, metoprolol, some antidepressants, metformin, ranitidine, ofloxacin, selegiline, etc.). In this regard, alternative medications for patients who often have to undergo such screening have been proposed. Some possibilities of unintentionally or intentionally inducing false negative results have also been highlighted. Popular approaches to fooling the screening test are diluting the urine, adding adulterants (marketed products or homemade chemicals), and providing foreign or synthetic urine. Summarizing the possible sources of errors in drug screening is expected to objectify the interpretation of the obtained results.

Background: The present study aims to develop the use of glutathione copper complex for the detection of sarcosine, a marker for prostate cancer. The glutathione-copper complex was successfully synthesized at room temperature and characterized using FTIR, UV, and Scanning Electron Micrograph. Methods: The structure of the glutathione copper complex was found to be a 1:2 Metal: Ligand ratio. The cyclic voltammogram for the glutathione-copper complex modified electrode showed an oxidation peak around -0.037 V, which indicates the irreversible oxidation of copper ions. The addition of sarcosine decreased the oxidation potential of the glutathione copper complex indicating the ability of the working electrode, for the detection of sarcosine in the sample using differential pulse voltammetry. Results: The results indicated that the glutathione-copper complex modified electrode revealed good sensitivity, selectivity, and linearity against the detection of sarcosine in the range from 0.1 μM to 2.5 μM. The LOD and LOQ were calculated using a linear prediction model, the data obtained from differential pulse voltammetry technique for known and simulated urine samples was 0.72 μM, 5.13 μM, and 1.45 μM, 39.94 μM, respectively. The sensitivity for the developed working electrode obtained for the known and simulated sample was 0.0567 μA/μM and 0.02913 μA/μM, respectively. Conclusion: Thus, we concluded that the glutathione copper complex decorated glassy carbon electrode is a good candidate for the detection of sarcosine with good selectivity and sensitivity for real-time monitoring.

Background: Surface plasmon resonance (SPR) based fibre optic sensors are becoming increasingly popular in biomedical applications. However, the sensor performance is degraded because of low sensitivity with inadequate detection accuracy and figure of merit. Objectives: The first objective of this study is to design a D-shaped photonic crystal fibre (PCF) using COMSOL multiphysics. The second objective is to enhance the performance of the designed sensor in terms of sensitivity and detection accuracy using single and dual metal layer structures. In addition, the performance of the proposed sensor is compared with the existing one. Methods: In this study, the performance of the PCF-SPR sensor is improved using a D-shaped photonic crystal fibre (PCF) and two metals as grating layers. The work in this paper is divided into two parts. In the first part, the gold metal layer with optimized thickness is used to achieve good sensitivity. In the second part, the combination of gold and silver dual metal layers with optimized thickness is used to achieve good detection accuracy. Moreover, the performance of the proposed sensor is compared to other published D-shaped PCF sensors. Results: The proposed D-shaped PCF-SPR sensor is designed and simulated using COMSOL multiphysics. The results in terms of sensitivity (S) and detection accuracy (DA) are obtained using a single metal layer and dual metal layers with optimum thickness. Moreover, the transmission coefficient and loss curve have been calculated using different refractive indices of the material. In addition, the simulation results are validated for cancer detection using the proposed sensor. Conclusion: An improvement of the D-shaped PCF sensor for cancer detection is presented in terms of S and DA using single or dual metal layer structures and COMSOL multiphysics. In a single metal layer structure, only gold is used as a grating layer, and the thickness of the grating layer is optimized for achieving high sensitivity. Similarly, a combination of gold and silver is used as the grating layer in the dual metal layer structure for achieving a high DA. Moreover, the obtained results of the proposed PCFSPR sensor are compared with the published results and found that the proposed sensor can be used with a high degree of S and DA for biomedical applications and also can be used in the bio-sensing field.

Background: Astragalus, as a common traditional Chinese medicine (TCM), has many pharmacological effects, such as protection of nerves, heart, blood vessels, kidneys, etc. It can also be used to treat colds, numbness, diarrhea, indigestion, and anemia. Because of the current market, there are a large number of synonyms, synonyms, and multiple sources of one medicine. The use of near-edge plants in medicine and other fake, substandard as a good phenomenon also prevails. Methods: In this study, a method combining electrochemical fingerprinting with SPSS software was developed to identify the origin of Astragalus membranaceus. The electrochemical fingerprints of Astragalus membranaceus with different accessions and different origins were examined using an electrochemical workstation. Then the characteristic parameters were selected to achieve the origin identification of Astragalus with SPSS software using cluster analysis and discriminant analysis. Results: The results of this method divided the origin of Astragalus into the Qinling production area and other production areas Conclusion: This method can be used to identify the origin of Astragalus membranaceus, which provides a new method to identify Astragalus membranaceus and other TCM without extracting the active ingredients of Chinese medicines, in line with the traditional "holistic" treatment concept of TCM.

Background: Hydrogen peroxide (H2O2) is an important metabolite that plays a crucial role in enzymatic reactions in living organisms. However, it acts as a reactive oxygen species (ROS) that causes various chronic diseases. The main challenging aspects in detecting H2O2 in body cells are the ultra-lowlevel concentrations and its reactivity. Hence, it is highly essential to develop a platform for H2O2 with high sensitivity and selectivity. Objective: In this work, we report an electrochemical biosensor for hydrogen peroxide (H2O2) by interfacing 3-dimensional silver nanoparticles (Ag-NPs) with 2-dimensional hematene (HMT) nanosheets. Methods: The two-dimensional nanomaterial, HMT, was exfoliated from natural iron ore hematite (α- Fe2O3) and characterized by Raman spectroscopy. The morphology of the Ag nanoparticles and HMT was imaged by scanning electron microscope. Electrochemical characterization of Ag/HMT modified glassy carbon electrode (GCE) was performed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Results: The fabricated sensor showed a wide linearity range of H2O2 concentrations from 0.99 μM to 1110 μM and a low detection limit of 0.16 μM using CV. Further, the sensor was successfully applied for the electrochemical sensing of hydrogen peroxide using chronoamperometry (CA) from 20 μM to 1110 μM (LOD 5.5 μM). Conclusion: The proposed electrochemical sensor for H2O2 is fast responding with a high sensitivity, and shows selectivity in the presence of biologically important molecules. These consequences suggested that the formation of heterostructures between 2D and 3D nanomaterials unveils the possibility of stable and selective electrochemical sensors for bioanalytics.

Background: In recent years, there have been tensions surrounding the accessibility of drugs at pharmacies. This situation has led people to turn to alternative medicine with increased use of plants as medicines. Nevertheless, a good knowledge of the plant's chemical composition is necessary for its proper use due to the presence of toxic products. Objective: The research objectives are to expand a novel use of the static headspace technique to control the chemical composition of the vapor of fennel seed tea (Foeniculum vulgare Mill.) and also constitute an attempt to develop a targeted qualitative analytical method for quality control and safety assurance of a consumer product. Methods: This study qualitatively investigated the amount of estragole in fennel herbal tea vapour by successful rehabilitation of the static headspace gas chromatography/mass spectrometry method. In addition, an analysis is conducted on the total phenolic and flavonoid content in both tea and methanol extract. Antioxidant activities of all extracts were measured and compared to Gallic acid. Results: The fennel seed tea showed total phenolic and flavonoid contents at 187.7 ± 17.1 GAE/100 g and 133.8 ± 9.07 mg CE/100 g, respectively. Fennel seeds tea exhibited good DPPH anti-radical action with an IC50 of 92.38 ± 10.64 mg/g. Even though studies on the total phenols, flavonoid contents, and antioxidant activity of this herbal tea have all yielded positive outcomes, the application of the static headspace method combined with gas chromatography and mass spectrometry indicated the presence of estragole at 37.63 ± 3.77%. This compound was found at 80.67 ± 0.29% in the essential oil. Conclusion: The application of this method has made it possible to reduce the handling time by eliminating the extraction step and solvent use. The presence of estragole at an alarming level makes it clear that employing plants as medicines must be regulated.

Objective: An improved amperometric D aminoacid (DAA) biosensor was fabricated by immobilizing covalently, D-amino acid oxidase (DAAO) onto nanocomposite of chitosan (CHIT)/ iron oxide nanoparticles (Fe3O4NPs)/ carboxylated multiwalled carbon nanotubes (cMWCNT)/ electrodeposited onto glassy carbon (GC) electrode. Methods: The iron oxide nanoparticles (Fe3O4NPs) were prepared and characterized by UV spectroscopy, transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Results: The enzyme electrode (DAAO/CHIT/ Fe3O4NPs/cMWCNT/GC) was characterized by scanning electron microscopy (SEM), FTIR and electrochemical impedance spectroscopy (EIS). The biosensor showed maximum response within 2s at pH 8.0, 35°C and potential of 0.09V vs. Ag/AgCl with a linear working range of 0.02-0.80 μM, sensitivity of 919.29 μAcm^-2μM^-1 and detection limit of 0.02 μM. Conclusion: The within and between batch coefficients of variation (CVs) for determination of DAA by present biosensor were 2.35% and 2.87%, respectively. The level of DAA in real fruit juices as measured by the present biosensor matched with those by the standard spectrophotometric method with a good correlation (r = 0.978). The biosensor lost 30 % of its initial activity over a period of 120 days when stored dry at 4°C.