Field Of Analytical Chemistry Research Articles

Percent residual accuracy for quantifying goodness-of-fit of linear calibration curves

Linear models for calibration curves are overwhelmingly created based on minimization of least squares error, with their goodness-of-fit (GOF) quantified using the square of the correlation coefficient (R2). Yet, R2 has well-known disadvantages when used to quantify GOF of calibration curves stemming from its calculation based on the absolute error of the signal (i.e., calculated vs. experimental). These disadvantages are exacerbated when using a geometric series of concentrations for calibration standards (e.g., 1, 2, 5, 10, etc.) and when calibration curves span 2–3 orders of magnitude, which is typical for modern analytical techniques. While there are multiple alternative GOF measures, R2 overwhelmingly persists in the field of Analytical Chemistry as the most reported measure of GOF. We evaluated R2, alternative GOF measures, and multiple quantitative bias parameters, along with residual analysis, for over 60 experimental calibration curves. R2 did a poor job of consistently and accurately quantifying the GOF over the entire calibration curve. This was especially true for situations where the low concentration calibrators were not accurately described by the calibration equation. While other GOF parameters, including the sum of the absolute percent error, mean absolute percent error, and quality coefficient, did a better job of describing GOF of calibration curves, each had significant theoretical and/or practical disadvantages. Therefore, we introduce a descriptive GOF parameter called Percent Residual Accuracy (%RA or PRA) which equally weights the accuracy of all calibrators into a single value, generally falling between 0% and 100%, with 100% representing a perfect fit and a “good” fit for calibration data producing a %RA of 90–100%. The %RA much more effectively described the GOF for the entire calibration range than R2, and it similarly quantified GOF as compared to the other GOF parameters tested. With the performance and practical advantages of %RA, we conclude that it is the most advantageous GOF parameter and that it should be reported as a standard GOF measure for calibration curves.

Multi mimetic Graphene Palladium nanocomposite based colorimetric paper sensor for the detection of neurotransmitters

Palladium in the form of G-Pd nanocomposite possesses multiple enzyme mimicking activity. It catalyzes the oxidation of dopamine, glutamate, H2O2 and NADH through dopamine oxidase, glutamate oxidase, peroxidase and NADH oxidoreductase biomimetic activity. Kinetic studies were performed to calculate the catalytic parameters of G-Pd nanocomposite towards the substrates for a potential heterogeneous catalyst. Among them, glutamate oxidase activity was coupled with peroxidase activity of G-Pd for the detection of glutamate, in the form of a paper based sensor. Analytical performance of G-Pd nanocomposite catalyzed glutamate detection was characterized, and found to be linear in the range 0–400 μM and 400–8000 μM with limit of detection and quantification of 49.4 μM and 117.9 μM respectively. Results from the present study provides substantial progress in the practical application of nanomaterials as heterogeneous catalysts with multi enzyme mimicking property. G-Pd nanocomposite overcomes the complexity of enzyme based biosensors due to less number of reagents, better stability due to the absence of enzymes with mild storage conditions. Multi-mimetic catalytic activity of Pd will find applications in the field of analytical chemistry, biosensors, energy, environment and food safety.

A review on analytical method development, optimization and validation of combination of Azithromycin and benzoyl peroxide by RP-HPLC using design of experiment as per ICH guideline

Pharmaceutical analysis is one of the most challenging fields of analytical chemistry. Pharmaceutical analysts carry out the qualitative and quantitative control of APIs and drug products and also develop and validate appropriate methods. One of my main goals was to develop modern, rapid, precise and reproducible, but also cost-effective HPLC assay methods which are generally available and applicable for most users. The aim of this work was to develop LC methods for both compounds. The assay of erythromycin by LC offers several advantages, such as high specificity, the possibility of determining and quantifying impurities and degradation products, and improved accuracy. The developed methods were validated. My whole work containing following plan of work as Selection of drug, Review Literature, FITR of both drugs and Mixture, Preparation of standard solutions, Preparation of sample of pure drug in Standard solution, Method development by HPLC (as Selection of solvents to be used as diluents and mobile phase, Selection of wavelength, Selection of mobile phase and Selection of chromatographic conditions) Preparation of Mobile phase, Preparation of standard calibration curve combination of drug, Optimization of HPLC condition using box behnken design. Validation of analytical method following parameters as per ICH guidelines. (i). System suitability (ii). Linearity and range (iii). Specificity (iv).Accuracy and precision (v). Limits of detection (LOD) and Quantitation (LOQ). (vi). Selectivity and (vii).Robustness.

One-step deposition of NixCu1−x alloys with both composition gradient and morphology evolution by bipolar electrochemistry

Bipolar electrochemistry is an unconventional but powerful technique in the fields of materials science and analytical chemistry. We report here the one-step cathodic deposition of NixCu1–x alloys with a composition gradient and a morphology evolution on a copper substrate, based on an in-plane potential gradient over the interface of a bipolar electrode (BPE) and an electrolytic solution. The alloy gradient was characterized using scanning and transmission electron microscopy techniques. As a result, the deposited alloy layer exhibits a composition gradient from 0 to ca. 89% Ni atoms corresponding to an abundant morphology evolution from pyramids to dendrites and to nano/microballs along the surface of the BPE. Electrochemical screenings were performed for the dissected alloy specimens as the electrocatalyst of hydrogen evolution reaction. The present work shows that bipolar electrochemistry can give access to the fabrication of alloys with abundant architectures as high throughput screening candidates.

Simultaneous Measurement of Viscosity and Optical Density of Bacterial Growth and Death in a Microdroplet.

Herein, we describe a novel method for the assessment of droplet viscosity moving inside microfluidic channels. The method allows for the monitoring of the rate of the continuous growth of bacterial culture. It is based on the analysis of the hydrodynamic resistance of a droplet that is present in a microfluidic channel, which affects its motion. As a result, we were able to observe and quantify the change in the viscosity of the dispersed phase that is caused by the increasing population of interacting bacteria inside a size-limited system. The technique allows for finding the correlation between the viscosity of the medium with a bacterial culture and its optical density. These features, together with the high precision of the measurement, make our viscometer a promising tool for various experiments in the field of analytical chemistry and microbiology, where the rigorous control of the conditions of the reaction and the monitoring of the size of bacterial culture are vital.

FORMATION OF STUDENTS’ SCIENTIFIC THINKING BASED ON THE LEARNING OF METHODS OF THE SUBSTANCE ANALYSIS

Introduction. In Federal State Standards of the Higher Education (FSS HE) of the natural-science and technical specialties and also in a number of the corresponding professional standards, the competence in the field of analytical chemistry is specified as one of the main qualification characteristics of an expert/university graduate. It is caused by interdisciplinarity of analytical chemistry and a wide range of application of analysis methods which are used today not only directly on chemical production, but also in power engineering, construction engineering, metallurgy, materials science, standardization, certification, and many other spheres. At the current time, however, there is a big gap between achievements of chemical science and content of high school discipline that reduces quality of staff training demanded in labour market. This discrepancy is caused both by preservation of traditional methodology of teaching chemistry and the reasons of the methodical plan. The aim of the publication is to search for more effective and productive ways of mastering the educational material that is relevant for acquiring the qualifications required from the university graduate. Methodology and research methods. Methodological framework of the article involves the concepts of chemical and natural-science education at the higher school; the principles of the system-based, cognitive, practice-focused and competence-based training. Results and scientific novelty. On the basis of the review and generalization of scientific and methodological resources on the theory and practice of application of the analysis methods of substances from didactic positions, a number of these methods have been singled out and compared; their role and features in determination of a molecule structure and other characteristics of an individual substance and its solutions have been shown. Despite the fact that the work is carried out using known methods of analysis, such a generalization makes it possible to more clearly understand the principles of the choice of a method and the method importance according to the purposes and specifics of the studied object that is essential for formation of research skills during training, as well as for formation of scientific thinking and the required qualification acquisition by graduates of the natural-science and technical specialties. In order to update the acquired knowledge, the examples illustrating applied use of various analysis methods in modern research and production practice have been collected. Tables have been made for a faster perception of the material by methods of analysis for the purpose of an informed choice of the method. Reliance on the principle of tabular collection of material makes it easier to understand the individuality of the method; allows teachers to reduce their workload; and on the part of students, to shorten the time and simplify the procedure of choosing the method of chemical, physicochemical and/or physical analysis. Practical significance. The work is compiled in accordance with the State General Educational Standards of Higher Professional Education, and can be recommended to practising and beginning teachers of higher education institutions, as well as graduate students of chemical specialties. The materials presented in the article can assist in designing the curricula of chemical disciplines or modules of educational programs.

A lab-on-a-tip approach to make electroanalysis user-friendly and de-centralized: Detection of copper ions in river water

The development of portable and user-friendly sensing platforms is a hot topic in the field of analytical chemistry. Among others, electroanalytical approaches exhibit a high amenability for reaching this purpose, i.e. the commercial strips for diabetes care are an obvious success. However, providing fully-integrated and user-friendly methods is the leitmotiv. In this work we evaluate the use of a disposable pipette tip, opportunely configured, to realize the first example of lab-on-a-tip. The combination of a pipette tip, wire electrodes, and cotton wool filter, highlights the suitability of producing a novel one-shot electroanalytical platform that does not require expertise-required tasks. To demonstrate the feasibility of this novel method, copper (Cu2+) is detected in water samples by means of anodic stripping voltammetry. The quantification is performed directly into the tip that contains a cotton wool filter: the filter has the double function of purifying the matrices from gross impurities and releasing all the pre-loaded reagents necessary for the assay. After optimizing the experimental parameters, the lab-on-a-tip was capable of detecting Cu2+ linearly up to 300 μg/L with a detection limit of 6.3 μg/L. The effectiveness of the platform was confirmed by testing 50, 100, and 150 ppb Cu-spiked river water sample with recovery value comprised between 92 and 103%.

In Vivo Imaging Technology of Transplanted Stem Cells Using Quantum Dots for Regenerative Medicine.

Quantum dots (QDs) have excellent fluorescence properties in comparison to traditional fluorescence probes. Thus, the optical application of QDs is rapidly expanding to each field of analytical chemistry. In this review paper, we reviewed the application of QDs to regenerative medicine, especially stem cell transplantation therapy. The labeling of stem cells using QDs composed of semiconductor materials in combination with a chemical substance, poly-cationic liposome and cell penetrating peptide is reported. In addition, the influence of QD labeling on the pluripotency of stem cells is also reported. Finally, the in vivo imaging of transplanted stem cells in mice by QDs emitting fluorescence in the near-infrared region, which can be detected by in vivo fluorescence imaging systems such as IVIS and SAI-1000, is described. The future prospects for stem cell imaging technology by QDs are also discussed.

Covalent bonding of Schiff base network-1 as a stationary phase for capillary electrochromatography

Covalent organic frameworks (COFs), featuring low densities, high surface areas, and good thermal and chemical stabilities, are gradually attracting interest in the field of analytical chemistry. A type of microporous polymer network material named Schiff base network-1 (SNW-1) was introduced into a capillary column through covalent bonding. The obtained SNW-1-coated capillary column was characterized by thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Then, the SNW-1-coated capillary column was successfully utilized for the open-tubular capillary electrochromatography (OT-CEC) separation of sulfonamides, cephalosporins, amino acids and parabens. The fabricated capillary column showed good separation efficiency (Rs > 1.4), stability and reproducibility (relative standard deviation (RSD) < 5.88%). To the best of our knowledge, this is the first report of a covalent bonding strategy to bond an SNW material to a capillary column for OT-CEC.

Ionic liquids as signal amplifiers for the simultaneous extraction of several neurotransmitters determined by micellar electrokinetic chromatography

Nowadays, ionic liquids (ILs) are receiving more attention in various fields of analytical chemistry. Their contribution to the enhancement of the clean-up, extraction, separation and determination of trace amounts of various biologically important compounds in distinct matrices is well documented. Moreover, their importance as "green chemistry" solvents has been pointed out. Advanced analytical methods based on the IL-assisted microextraction and electrophoretic determination of minute concentrations of neurotransmitters (NTs) in samples are presented here for the first time. In this paper, experimental data showed the usefulness of the chosen imidazolium-based ILs in solid-phase microextraction (SPME), followed by the micellar electrokinetic chromatography (MEKC) determination of three biogenic amines: dopamine, noradrenaline and adrenaline together with such amino acids as L-tyrosine and L-tryptophan. A significant increase in SPME yields, using 1-ethyl-3-methylimidazolium tetrafluoroborate as a component of the desorbent, allowing from 9 to 21 times the signal enhancement for the selected NTs, has been achieved. The elaborated IL-based SPME procedures might serve as a straightforward analytical platform for the unbiased analysis of NTs as biomarkers of various diseases where an unbalanced secretion of NTs is registered.

Exploration of Nanoparticle-Mediated Photothermal Effect of TMB-H2O2 Colorimetric System and Its Application in a Visual Quantitative Photothermal Immunoassay.

The exploration of new physical and chemical properties of materials and their innovative application in different fields are of great importance to advance analytical chemistry, material science, and other important fields. Herein, we, for the first time, discovered the photothermal effect of an iron oxide nanoparticles (NPs)-mediated TMB (3,3',5,5'-tetramethylbenzidine)-H2O2 colorimetric system, and applied it toward the development of a new NP-mediated photothermal immunoassay platform for visual quantitative biomolecule detection using a thermometer as the signal reader. Using a sandwich-type proof-of-concept immunoassay, we found that the charge transfer complex of the iron oxide NPs-mediated one-electron oxidation product of TMB (oxidized TMB) exhibited not only color changes, but also a strong near-infrared (NIR) laser-driven photothermal effect. Hence, oxidized TMB was explored as a new sensitive photothermal probe to convert the immunoassay signal into heat through the near-infrared laser-driven photothermal effect, enabling simple photothermal immunoassay using a thermometer. Based on the new iron oxide NPs-mediated TMB-H2O2 photothermal immunoassay platform, prostate-specific antigen (PSA) as a model biomarker can be detected at a concentration as low as 1.0 ng·mL-1 in normal human serum. The discovered photothermal effect of the colorimetric system and the developed new photothermal immunoassay platform open up a new horizon for affordable detection of disease biomarkers and have great potential for other important material and biomedical applications of interest.

Consensus Classification Using Non-Optimized Classifiers.

Classifying samples into categories is a common problem in analytical chemistry and other fields. Classification is usually based on only one method, but numerous classifiers are available with some being complex, such as neural networks, and others are simple, such as k nearest neighbors. Regardless, most classification schemes require optimization of one or more tuning parameters for best classification accuracy, sensitivity, and specificity. A process not requiring exact selection of tuning parameter values would be useful. To improve classification, several ensemble approaches have been used in past work to combine classification results from multiple optimized single classifiers. The collection of classifications for a particular sample are then combined by a fusion process such as majority vote to form the final classification. Presented in this Article is a method to classify a sample by combining multiple classification methods without specifically classifying the sample by each method, that is, the classification methods are not optimized. The approach is demonstrated on three analytical data sets. The first is a beer authentication set with samples measured on five instruments, allowing fusion of multiple instruments by three ways. The second data set is composed of textile samples from three classes based on Raman spectra. This data set is used to demonstrate the ability to classify simultaneously with different data preprocessing strategies, thereby reducing the need to determine the ideal preprocessing method, a common prerequisite for accurate classification. The third data set contains three wine cultivars for three classes measured at 13 unique chemical and physical variables. In all cases, fusion of nonoptimized classifiers improves classification. Also presented are atypical uses of Procrustes analysis and extended inverted signal correction (EISC) for distinguishing sample similarities to respective classes.

Synthesis of Optode Thin Layer using Sol Gel Hybrid of Trietoxysiloxane monomer and 3-(Trimethoxysilyl) Propilamine with Ionophore 4-(2-Pyridilazo)-1,3-Benzenadiol (PAR)

Optode (Optical sensors) is one of the modern chemical sensors in the field of analytical chemistry that has utilized of inorganic polymers. The optode based on MLCT (Metal to Ligand Charge Transfer) (or MMLL’CT, Mixing Metal-Ligand to Ligand Charge Transfer) or LMCT (Ligand to Metal Charge Transfer) phenomenons have beed generated from oktyltrietxysilane, aminopropyltrimethoxysilane and 4-(2-pyrydilazo) resorcinol (abbreviated as OTES-APTS-PAR) for Cu(II), Cr(III), Ni(II), Fe(III), Cd(II), and Zn(II) ions target. The syntheses of thin layer optode were performed by sol gel method followed by evaporation in glass substrat. The formation of 4-(2-pyrydilazo) resorcinol complexes with ions target have gained strong absorption spectras in visible region because of charge transfer phenomenons. The optical sensor of OTES-APTS-PAR was analysed thermal properties using Differential Thermal Analysis (DTA). DTA thermogram showed a glass transition peaks at a temperature of 315.5 °C. Fourier transform Infrared (FTIR) spectras have showed that the optode materials consisted NH aryl groups indicated IR absorption at 1577.7 cm-1 and also –CH aromatic at 1469.0 cm-1. Synthesized optode materials have strong broad visible absorption with the maximum wavelengths (λmax) = 405 nm and 508.5 nm, respectively. This material have excellent optical responds to several metal ions such as Cu(II), Cr(III), Ni(II), Fe(III), Cd(II), and Zn(II) that was showed from huge Δλmax and the increase of Ktotal

The future of analytical chemistry in foodomics

The field of food analytical chemistry has greatly evolved over the last years, moving from the descriptive view of raw food composition into the modern instrumental approaches known as the foodomics. The development and optimization of these integrated approaches, based on the use of high resolution techniques for tracing the chemical fingerprint of a food, is arriving to define molecular parameters for the qualification, authentication, and safety of the products. With these new tools, omics are solving some of the new issues of food quality and traceability, including the development of analytical methods to ensure the origin of food, as well as the discovery of biomarkers to identify potential food safety problems. Here we review the main methods used in foodomics from its birth until now, highlighting the use of high throughput instrumentation. This includes the computational problems they generate, but also the significant prospects for development of knowledge that are able to open in important areas such as food technology and biotechnology.

Kinetics and Mechanism of the Thermal and Hydrolytic Decomposition Reaction of Rosocyanin

ABSTRACTSpiroborate esters of curcumin find applications in the field of medicinal and analytical chemistry. The present paper reports the hydrolytic and thermal stability of rosocyanin, a 1:2 spiroborate ester of curcumin used for the photometric estimation of boron in different matrices. The effect of temperature, pH, and solvents was monitored spectrophotometrically for the hydrolysis of rosocyanin. The reaction followed first‐order kinetics, and the reaction rate enhanced with an increase in the percentage of water in an aqueous organic mixture, temperature, and pH. 11B NMR and UV–visible spectra were used to identify the hydrolysis product. The possible mechanistic route for the hydrolysis of rosocyanin was proposed. Solid‐state stability of rosocyanin was investigated by thermogravimetric analysis, and the data were analyzed using different solid‐state reaction models to find the suitable reaction model. Kinetic parameters associated with its thermal decomposition were calculated using Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose isoconversional methods and were compared.

Biphasic nickel phosphide nanosheets: Self-supported electrocatalyst for sensitive and selective electrochemical H2O2 detection and its practical applications in blood and living cells

Abstract Electrochemical nonenzymatic detection has received enormous attentions from analytic chemistry communities. However, the complicated design and fabrication procedures of electrocatalysts hinder its practical application. Pursing of simple and direct synthesis route is vital and desirable to minimize the discrepancy between electrodes, and is essential for implementing of reliable detection. Herein, we propose a one-step synthesis strategy for direct phosphidation of nickel foam (NF) to fabricate effective biphasic nickel phosphide nanosheets (BNPNS) electrocatalyst. This self-supported BNPNS electrocatalyst realizes sensitive and selective electrochemical nonenzymatic detection of hydrogen peroxide (H2O2) with wide concentration regions. Benefiting from its high sensitivity, low detection limit, wide sensing range, and good reproducibility, repeatability, stability, the BNPNS has been successfully employed to detect H2O2 in practical samples of human blood and living cells. The simple and straightforward preparation process of BNPNS opens up a new avenue for practical applications of non-noble metal based electrocatalysts in analytical chemistry field for reliable detections.

Ultrasensitive Detection of Capsaicin in Oil for Fast Identification of Illegal Cooking Oil by SERRS.

Discrimination of illegal cooking oil is a conundrum in the fields of analytical chemistry and food safety due to complicated sample systems, lack of common targets, and stringent demand of ultrahigh detection sensitivity for corresponding analytical methods. Capsaicin, one of the exogenous molecules that is subsistent in recycled kitchen waste oils, can be regarded as a target for illegal cooking oil identification. Nowadays, tracing capsaicin in oils is implemented mainly by high-performance liquid chromatography–mass spectrometry, which displays shortcomings in high costs and incapableness for field test. Here, we established a surface-enhanced resonance Raman scattering approach to detect capsaicin and identify illegal cooking oils by means of the molecular derivatization treatment of capsaicin. This method features high detection sensitivity with the detection limit of 1.0 × 10–8 M, rapid response (<7 min detection duration), and simplicity in sample pretreatment, which is available for fast field test of illegal cooking oils.

Light-Emitting Devices Based on Electrochemiluminescence: Comparison to Traditional Light-Emitting Electrochemical Cells

Electrochemical processes can be exploited to operate light-emitting devices with unusual functionality. For example, light-emitting electrochemical cells (LECs) contain a small amount of electrolyte within the organic/polymer light-emitting active layer. The electrolyte in the active layer allows the multiple charge injection layers that are deemed critical for organic light-emitting diodes to be avoided. Very recently, an alternative light-emitting device platform based on electrochemical processes was also suggested. These devices rely on electrochemiluminescence (ECL), a light-emission process based on the charge transfer reaction between reduced and oxidized forms of luminophores. Although the ECL process has been extensively investigated in the field of analytical chemistry, its utilization in electronic devices is a new approach that offers unique opportunities. Despite the interesting opportunities, a good introduction to the subject is not available, particularly with a focus on electronic device...

Introductory Note to the Special Issue of “Analytical Letters” for the International Conference: 10th Aegean Analytical Chemistry Days (AACD 2016)

ABSTRACTThis special issue of ‘Analytical Letters’ is devoted to selected papers based on contributions from the 10th Aegean Analytical Chemistry Days (AACD 2016) International Meeting. The first AACD Meeting was held in Izmir-Turkey in 1998 for enhancing the scientific collaboration of analytical chemists from Aegean countries primarily comprising Turkey and Greece, but these series of conferences later evolved into a successful international event covering the entire field of analytical chemistry practiced in almost all countries. Selected papers from most of these conferences were published in the special issues of reputable journals. Specifically in this special edition, the authors have extended their conference proceedings papers and added their latest experimental results. The papers have undergone the standard review process. The AACD 2016 Conference, providing a forum among analytical chemistry researchers from many different countries, was held in Çanakkale, jointly hosted by Çanakkale Onsekiz Mart University (ÇOMU) and Istanbul University (IU). AACD 2016 combined invited lectures, parallel oral sessions and poster presentations, altogether comprising 14 invited lectures, 45 contributed oral presentations and 343 posters, and three company presentations. The selected best 40 posters were orally presented for 5 min at the ‘flash poster presentation’ session. The Conference Organizers are thankful to the AACD Continuation Committee, invited speakers and all presenters, authors and reviewers who were willing to share their expertise with us by submitting/reviewing the valuable contributions to this special issue, and finally to the Chief Editor of ‘Analytical Letters’ and Taylor & Francis who handled the complete review process.

Interfacial contributions of H2O2 decomposition-induced reaction current on mesoporous Pt/TiO2 systems

We report on conversion of energy released due to chemical reactions into current for the decomposition of aqueous hydrogen peroxide solution on single phases Pt and TiO2, in addition to Pt and TiO2 simultaneously. We observe that H2O2 decomposition-induced current on TiO2 drastically overshadows the current generated by H2O2 decomposition on Pt. Photo-effects avoided, H2O2 decomposition was found to yield a conversion efficiency of 10−3 electrons generated per H2O2 molecule. Further understanding of chemical reaction-induced current shows promise as a metric with which the surface reaction may be monitored and could be greatly extended into the field of analytical chemistry.