Current Analytical Chemistry - Volume 16, Issue 5, 2020

Nowadays, most advanced technologies utilize materials from finite non-renewable resources, such as fossil fuels, minerals, and metal ores. With the recent attention on exploring substitutes to non-renewable resources and highlighting the reduced environmental impacts, researches are progressively being focused at the development of biodegradable materials from biocomposite and biopolymer-based materials. This review paper aims at reporting on very recent development in biopolymer and biocomposite. Biocomposites cater to a substantial non-food market for agro residuederived resins and fibres. Recently, biopolymer and biocomposite with controllable lifespans have become a main subject for various applications and fields. This paper is a timely review since there has been recent renewed attention in research studies, for both industry and academia concerning the development of new generation of biocomposite and biopolymerbased materials having potential uses in other areas.

Background: Blue is a color not often present in food. Even so, it is especially attractive to children. Today, most blue coloring agents used by the food industry are synthetic. With increasing health issues concern by the scientific community and the general population, there is a trend to look for natural alternatives to most synthetic products. There only exist few natural blue colorants, which are presented in a literature survey, along with the methods currently used for their recovery from natural sources. The best extraction methods and process parameters for the extraction of blue anthocyanins, iridoids and phycocyanin are discussed. Methods: A literature survey was conducted to detect the main sources of blue colorants found in nature. The focus was on the extraction methods used to recover such molecules, with the objective of finding efficient and environmentally safe techniques for application at industrial level, and, thus, allowing the production of natural blue colorants at scale high enough for food industry consumption. Results: The main natural blue colorants found in literature are anthocyanins, phycocyanin, and genipin. While anthocyanins can be recovered from a variety of plants, the source of phycocyanin are algae, and genipin can be obtained specifically from Gardenia jasminoides Ellis and Genipa americana L. Several extraction techniques have been applied to recover blue colorants from such sources, from classical methods using organic solvents, to more sophisticated technologies as ultrasoundassisted extraction, supercritical fluid extraction, pressurized liquid extraction, high-pressure extraction, and enzyme-assisted extraction. Conclusion: There is great potential for anthocyanins, phycocyanin and genipin use as natural food additives with health benefits, besides imparting color. However, the technologies for the colorants recovery and application are not mature enough. Therefore, this area is still developing, and it is necessary to evaluate the economic feasibility of the proposed extraction processes, along with the safety and acceptance of colored food using these additives.

Background: Aristolochic acids are chemically linked to nitrophenanthrene carboxylic acids which are found in aristolochia plants. These compounds are intrinsically carcinogenic, while they have been used in traditional medicine from a long time ago. Despite the beneficial effects of herbals for treating some diseases, they possess some side effects. Methods: Therefore, the development of a sensitive and selective procedure for the determination of these harmful components in various complicated samples is an important task for health systems and drug authorities. In the past years, ultra-pressure liquid chromatography, high performance liquid chromatography and capillary electrophoresis with different detection systems were used for determination of aristolochic acids in various samples. Results: In this review, different analytical methods have been discussed in brief and applications of them in diverse samples have been summarized. Conclusion: Different approaches are compared from point of sensitivity, selectivity, and extraction efficiency.

Background: TLC bioautography is a hyphenated technique combining planar chromatographic separation and in situ biological activity detection. This coupled method has been receiving much attention in screening bio-active natural products because of its properties of being simple, rapid, inexpensive, and effective. Methods: The recent progress in the development of method of TLC bioautography for detecting antimicrobial and enzyme inhibitory activities dating between 2012 and early 2018 has been reviewed. The applications of this method in biological screening of natural products were also presented. Results: Some anaerobic and microaerophilic bacteria and a causative bacterium of tuberculosis have been adopted to TLC direct bioautography. Seven types of enzymes including acetylcholinesterase, glucosidase, lipase, xanthine oxidase, tyrosinase, monoamine oxidase, and dipeptidyl peptidase IV have so far been adopted on TLC bioautography. Its new application in screening antiurolithiatic agents was included. Conclusion: The standard experimental procedures are required for TLC antioxidant and antimicrobial assays. Some new enzymes should be attempted and adopted on TLC bioautography. The existing TLC methods for enzyme inhibition need more application studies to assess their screening capacity in the discovery of active compounds. The GC-MS or LC-MS approaches have gradually been coupled to TLC bioautography for fast structural characterization of active compounds.

Background: Multiple Sclerosis (MS) involves an immune-mediated response in which body’s immune system destructs the protective sheath (myelin). Part of the known MS biomarkers are discovered in cerebrospinal fluid like oligoclonal lgG (OCGB), and also in blood like myelin Oligodendrocyte Glycoprotein (MOG). The conventional MS diagnostic methods often fail to detect the disease in early stages such as Clinically Isolated Syndrome (CIS), which considered as a concerning issue since CIS highlighted as a prognostic factor of MS development in most cases. Methods: MS diagnostic techniques include Magnetic Resonance Imaging (MRI) of the brain and spinal cord, lumbar puncture (or spinal tap) that evaluate cerebrospinal fluid, evoked potential testing revealing abnormalities in the brain and spinal cord. These conventional diagnostic methods have some negative points such as extensive processing time as well as restriction in the quantity of samples that can be analyzed concurrently. Scientists have focused on developing the detection methods especially early detection which belongs to ultra-sensitive, non-invasive and needed for the Point of Care (POC) diagnosis because the situation was complicated by false positive or negative results. Results: As a result, biosensors are utilized and investigated since they could be ultra-sensitive to specific compounds, cost effective devices, body-friendly and easy to implement. In addition, it has been proved that the biosensors on physiological fluids (blood, serum, urine, saliva, milk etc.) have quick response in a non-invasive rout. In general form, a biosensor system for diagnosis and early detection process usually involves; biomarker (target molecule), bio receptor (recognition element) and compatible bio transducer. Conclusion: Studies underlined that early treatment of patients with high possibility of MS can be advantageous by postponing further abnormalities on MRI and subsequent attacks. This Review highlights variable disease diagnosis approaches such as Surface Plasmon Resonance (SPR), electrochemical biosensors, Microarrays and microbeads based Microarrays, which are considered as promising methods for detection and early detection of MS.

Background: Bisphenol A (BPA) is considered one of the most common chemicals that could cause environmental endocrine disrupting. Therefore, there is an increasing demand for simple, rapid and sensitive methods for BPA detection that result from BPA leaching into foods and beverages from storage containers. Herein, a simple laccase electrochemical biosensor was developed for the determination of BPA based on Screen-Printed Carbon Electrode (SPCE) modified graphenegold/ chitosan. The synergic effect of graphene-gold/chitosan nanocomposite as electrode modifier greatly facilitates electron-transfer processes between the electrolyte and laccase enzyme, thus leads to a remarkably improved sensitivity for bisphenol A detection. Methods: In this study, laccase enzyme is immobilized onto the Screen-Printed Carbon Electrode (SPCE) modified Graphene-Decorated Gold Nanoparticles (Gr-AuNPs) with Chitosan (Chit). The surface structure of nanocomposite was studied using different techniques including Field Emission Scanning Microscopy (FESEM), TRANSMISSION Electron Microscopy (TEM), Raman spectroscopy and Energy Dispersive X-ray (EDX). Meanwhile, the electrochemical performances of the modified electrodes were studied using Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV). Result: The developed laccase biosensor offered excellent analytical performance for the detection of BPA with a sensitivity of 0.271 μA/μM and Limit of Detection (LOD) of 0.023 μM, respectively. Moreover, the constructed biosensor showed good reproducibility, selectivity and stability towards BPA. The sensor has been used to detect BPA in a different type of commercial plastic products as a real sample and satisfactory result was obtained when compared with the HPLC method. Conclusion: The proposed electrochemical laccase biosensor exhibits good result which is considered as a promising candidate for a simple, rapid and sensitive method especially in the resource- limited condition.

Background: The investigation of human bones unearthed from necropolises is a useful tool to enhance our knowledge about ancient cultures. In the present study, the possibility of using the activation energy (EA) values of thermogravimetric degradation processes coupled with exploratory analysis methods in order to investigate human remains, has been tested. Methods: Several human bones from four distinct necropolises have been analyzed by thermogravimetry and then thirteen different approaches have been used to estimate their activation energy of the degradation processes of carbonate and collagen. The entire set of data has been analyzed by Principal Component Analysis (PCA) in order to draw some preliminary considerations over the remains. Results: PCA analysis highlighted the possibility of recognizing grouping tendencies related to the funeral ritual bodies underwent and/or their age. Additionally, in the second part of the work, where the focus is on the activation energies of collagen and carbonates degradation processes estimated by the method which was considered the most reliable (i.e., the Arrhenius formula with the third order decay), some tentative considerations about a trend in cremation temperatures are drawn. Conclusion: The estimation of values from thermogravimetric signals combined with chemometrics is a useful tool for the investigation of bone samples, which allow obtaining additional info about trends and/or grouping tendencies in complex systems as human remains.

Background: Dichromate (Cr2O7^2-) ion is one of the carcinogenic and toxic spices in environment which can easily contaminate the environment due to its high solubility in water. Therefore, a lot of attention has been focused on the detection of Cr2O7^2- with high sensitivity and selectivity. Methods: In present work, nitrogen-rich precursor was used for synthesizing graphitic carbon nitride (g-C3N4) nanostructures through hydrothermal oxidation of g-C3N4 nanosheets. The prepared nanostructures show two distinct fluorescence emissions centered at 368 and 450 nm which are highly sensitive toward Cr2O7^2- ions. Results: The as-prepared g-C3N4 was characterized by several techniques such as Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and fluorescence emission spectra. The XRD pattern of prepared nanostructures illustrated two diffraction patterns (at 13.4° and 27.6°) indicating tri-s-tri-azine-based structures. The g-C3N4 exhibited good selectivity and sensitivity toward Cr2O7^2- among other anions. According to titration test, the detection limit and stern-volmer constant (Ksv) were calculated as 40 nM and 0.13×106 M-1, respectively. The investigation of quenching mechanism shows that Cr2O7^2- may form hydrogen bonding with surface groups of g-C3N4 (such as NH2, OH and COOH) resulted in more fluorescence quenching in comparison with the pure inner filter effect. Conclusion: The g-C3N4 nanostructures were successfully synthesized through the hydrothermal oxidation. The as-prepared g-C3N4 can be used as a highly sensitive fluorescent probe for the selective determination of Cr2O7^2- ion among other anions. The quenching mechanism was experimentally studied. According to reliable responses in real sample tests, it can be proposed that g-C3N4 nanostructure is a suitable sensitive nanosensor for detection of Cr2O7^2- ions in aqueous media.

Background: Ticagrelor is a highly recommended new antiplatelet agent for the treatment of patients with acute coronary syndrome at moderate or high ischemic risk. There is a real need for rapid and accurate analytical methods for ticagrelor determination in biological fluids for pharmacokinetic studies. In this study, a sensitive and specific LC-MS method was developed and validated for quantification of ticagrelor and its Active Metabolite (AM) in human plasma over expected clinical concentrations. Methods: Samples were handled by Liquid-Liquid Extraction (LLE). A linear gradient was applied with a mobile phase composed of formic acid 0.1% and acetonitrile with 0.1% of formic acid using a C18 reversed-phase column. MS spectra were obtained by electrospray ionization in negative mode and optimized at 521.4→360.9 m/z, 477.2→361.2 m/z and 528.1→367.9 m/z transitions for ticagrelor, AM and ticagrelor-d7, respectively. Results: This method allowed rapid elution, in less than 4 minutes, and quantification of concentrations as low as 2 ng/mL for ticagrelor and 1 ng/mL for AM using only 100 μL of human plasma. LLE using hexane/ethyl acetate (50/50) was an optimal compromise in terms of extraction recovery and endogenous compounds interference. Trueness values of 87.8% and 89.5% and precisions of 84.1% and 93.8% were obtained for ticagrelor and AM, respectively. Finally, the usefulness of the method was assessed in a clinical trial where a single 180 mg ticagrelor was orally administered to healthy male volunteers. Pharmacokinetic parameters of ticagrelor and its active metabolite were successfully determined. Conclusion: A sensitive and specific quantification LC-MS-MS method was developed and validated for ticagrelor and its active metabolite determination in human plasma. The method was successfully applied to a clinical trial where a single ticagrelor 180 mg dose was orally administered to healthy male volunteers. The described method allows quantification of concentrations as low as 2 ng/mL of ticagrelor and 1 ng/mL of the metabolite using only 100 μL of plasma.

Background: Type 2 diabetes mellitus is an expanding health problem. Binary antidiabetic combinations of Metformin Hydrochloride (MET) with either Saxagliptin Hydrochloride (SAX), or Dapagliflozin (DAP) are widely used. Review of the literature revealed that no single HPTLC method has been reported for the simultaneous determination of MET, SAX, and DAP allowing the determination of binary mixtures of any two of the three cited drugs in their tablets using the same experimental conditions, an important advantage for quality control. The advantages of HPTLC method relies on the simultaneous analysis of a large number of samples in a shorter analysis time, less solvent consumption, and less expenses, compared with HPLC. Objective: The objective of the proposed method is to develop and validate a single and simple HPTLC densitometric method for the simultaneous determination of MET, SAX, and DAP. Methods: Separation was performed using aluminum HPTLC sheets coated with silica gel 60 F254 with a mobile phase consisting of a mixture of acetonitrile: 1% w/v ammonium acetate in methanol (9: 1, v/v). Scanning was performed at 210 nm. Results and Discussion: Linearity of the method was assessed in the concentration range of 0.25-10 μg/band for SAX and DAP and 0.25-25 μg/band for MET. The method was fully validated as per the ICH guidelines. The proposed method provided error and deviation values of less than 2% assessing good accuracy and precision. Conclusion: The method was successfully applied to the analysis of pharmaceutical tablets of MET/SAX, MET/DAP, and SAX/DAP with high specificity.

Background: Iron is an essential transition metal which is indispensable for life processes like oxygen transport and metabolism, electron transfer etc. However, misregulated iron is responsible for disease like anemia, hemochromatosis, Alzheimer’s and Parkinson’s disease. In order to encounter these diseases, a better understanding is needed of its role in misregulation. Fluorescent iron sensors could help provide this information. The new chemosensor developed by linking a cyclohexane unit with three 8-hydroxyquinoline provides selective detection of iron in numerous biological and environmental samples. Methods: The Uv-visible and fluorescence spectroscopy in combination with pH measurements will mainly be used for the study. Theoretical studies at DFT level will be used to validate the method and explain the theory behind the experiments. Results: The study of electronic spectra of the chelator, HQCC, reveals the appearance of a band at 262 nm along with a weak band at 335 nm due to π- π* and n- π* transitions respectively. Upon excitation with 335 nm, the ligand fluoresces at 388 nm wavelength. The intensity of the emission was affected in presence of metal ions, with maximum deviation for Fe(III). Selectivity studies showed that Fe(III) is more selective as compared to the biologically relevant metal ions viz., Al(III), Fe(III), Cr(III), Co(II), Fe(II), Ni(II), Zn(II), Cu(II), Mn(II) and Pb(II). pH dependent studies implied that the fluorescence intensity was highest at pH ~8.0, whereas maximum quenching for iron-HQCC system was observed at pH 7.4. The binding studies from the B-H plot confirms the formation of 1:1 complex with association constant of 5.95 × 106. The results obtained from experiments were in agreement with that obtained from the DFT and TD-DFT studies. Conclusion: A novel tripodal chelator based on 8-hydroxyquinoline and symmetric cyclohexane scaffold was successfully developed. In addition to the excellence of the ligand to be employed as a promising sensitive fluorescent probe for easy detection of Fe3+ions at the physiological pH with very low concentration (7.5 x 10-5 molL-1), the new ligand can be used as an OFF-ON-OFF pH sensor. Fe(III) encapsulation along with 1:1 ML-complexation formation have been established. Theoretical studies confirm a d-PET mechanism for the fluorescence quenching. DFT studies revealed that the neutral form of the ligand is less reactive than its protonated or the deprotonated form.

Background: Trimethylamine (TMA) is a nitrogenous base aliphatic organic compound accounting for the odor of rotten fish and it is used as an indicator for analyzing the quality of fish products. Introduction: Extraction procedures and analytical methods including colorimetric and Gas- Chromatography (GC) can quantify the TMA contents of fish products after pre-treatment with basic solutions. However, the extraction procedure and analytical methods for acid-treated samples are not known, despite the majority of fish products being preserved using acid preservatives. Methods: The methodologies used included solid-phase micro-extraction of TMA followed by its quantification by a GC-based analytical method. An analysis of response surface methodology was also conducted to verify the optimum conditions for TMA detection in acid-treated liquid samples affected by factors including trapping time, temperature, and stirring speed. Results: The results obtained from this study showed that the optimum conditions for the best yield of TMA extraction are 20 min of trapping, emission at 55°C, and stirring at 400 rpm. The validation of the developed method was carried out using rotten fish after acid treatment. Acid treatment decreased TMA by up to 73.01%, however, when adding NaOH solution of the same volume to the samples, TMA increased similar to the control group. Conclusion: Here, we report a simple, sensitive, and rapid extraction procedure. A GC-based analytical method was developed for the analysis of TMA from the acid-treated sample. The developed extraction procedure and analytical methods were optimized and validated, which could be helpful for the extraction of TMA without damaging the sample.

Background: Aluminum Al(III) is the most significant metal in the earth's crust to which humans are frequently exposed and has several industrial applications. On the other hand, Al (III) has high potential toxic impacts on some human pathologies like Parkinson and Alzheimer's disease. So, it is very important to monitor and determine the trace level of Al (III) in various environmental and biological samples. Objective: In the present work, a novel green supramolecular Solvent-Based Liquid-Phase Microextraction (SS-LPME) procedure has been developed to preconcentrate and determine aluminum (III) in various real samples. Methods: The proposed procedure was based on the application of 1-decanol/THF as a Supramolecular Solvent (SS) system and quinalizarin as a chelating agent. Al(III)-quinalizarin hydrophobic complex was obtained at pH 7.0, extracted into supramolecular solvent phase (1- decanol/THF), centrifuged and then measured spectrophotometrically at 580 nm. The impact of different analytical parameters on the microextraction efficiency was studied and optimized. The validation of the proposed preconcentration procedure was checked using certified reference materials. Results: The calibration curve was linear in the range of 2.0-150 μg L-1. The developed method has preconcentration factor of 40 and detection limit (LOD) was 0.20 μg L-1. The precision of the method was confirmed with low relative standard deviation (RSD ≤ 1.0%). Conclusion: This study explores the effectiveness of quinalizarin for the first time together with SS to develop green SS-LPME method to preconcentrate and separate trace quantities of Al (III) in real water, fruit juice, food, hair, and urine samples collected from Saudi Arabia.

Background: An Ionic Liquid-based based Dispersive Liquid-Liquid Microextraction (IL-DLLME) method was not applied to preconcentration and determination of bilirubin. Ionic Liquids (ILs) are new chemical compounds. In recent years, Ionic Liquids (ILs) have been employed as alternative solvents to toxic organic solvents. Due to these perfect properties, ILs have already been applied in many analytical extraction processes, presenting high extraction yield and selectivity for analytes. Methods: In this study, IL-DLLME was applied to biological samples (urine and serum) for the spectrophotometric detection of bilirubin. For bilirubin analysis, the full-color development was based on the reaction with periodate in the presence of hydrochloric acid. The high affinity of bilirubin for the ionic liquid phase gave extraction percentages above 98% in 0.3 M HCl solution. Results: Several IL-extraction parameters were optimized and room temperature ionic liquid 1-butyl- 1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and ethanol were used as extraction and disperser solution. The linear range was found in the range of 0.5-6.0 μM (0.3-3.5 μg mL-1) and the limits of detection of the proposed method was 0.5 μM (0.3 μg mL-1). The proposed method was applied for the preconcentration and separation of trace bilirubin in real urine samples. Also, the recoveries for bilirubin in spiked biological samples (urine and serum) were found to be acceptable, between 95-102%. Conclusion: The proposed IL-DLLMEapproach was employed for the enrichment and determination of trace levels of bilirubin in urine samples using NaIO4 as an oxidizing agent and Uv-vis spectrophotometric detection. The periodate oxidation of bilirubin is rapid, effective, selective, and simple to perform. The method contains only HCl, NaOI4, and an anionic surfactant. The method may be useful for economizing in the consumption of reagents in bilirubin determining. The IL-DLLMEmethod ensures a high yield and has a low toxicity no skin sensitization, no mutagenicity and no ecotoxicity in an aquatic environment since only very low quantities of an IL is required. For full-color formation, no any extra auxiliary reagents are required. Besides, the IL-DLLME technique uses a low-cost instrument such as Uv-vis which is present in most of the medical laboratories.

Background: Amygdalin is a natural compound known for curing cancer. It is seen in several plants including in bitter almonds, apricots, peaches, apples, and plum seeds (kernels). Amygdalin is a toxic molecule containing a nitrile group, due to which toxic cyanide anion releases by the action of a β-glucosidase. The consumption of amygdalin may lead to cyanide poisoning in the human body. Therefore, for the first time, this work is aimed at developing a novel electrochemical biosensor for the detection of Amygdalin (AMG) in apple seed samples. Methods: The proposed electrochemical biosensor was fabricated by immobilizing cytochrome c (Cyt c) on a Glassy Carbon Electrode (GCE) with nanocomposite of cobalt ferrite nanoparticles (CoFe2O4 NPs) and functionalised multiwalled carbon nanotubes (f-MWCNTs). The characterization of the synthesized nanocomposite was performed with FTIR, TEM, TGA/DSC, and XRD techniques. Moreover, various experimental parameters such as the effect of pH, deposition time, sweep rate, potential, and enzyme incubation time and interference were also studied. Results: The fabricated biosensor enhanced the peak current by 10-folds compared to unmodified GCE. Under optimized experimental conditions, the biosensor exhibited linear response from 2 to 20 μM, with a linear regression equation Ipa (μA) = 8.4989 c + 6.6307 (R² = 0.9927). The LOD’s and LOQ’s were found to be 0.0112 μM and 0.2213 μM, respectively. Conclusion: The designed biosensor was successfully applied for the analysis of AMG content in the apple seed samples. The outcomes of this study identify the efficient electrocatalytic activity of the fabricated nanocomposite as significant electronic factors as major contributors to the electron transfer mechanism, with promising scope for the design of biosensor to sense toxic molecules.