Photochemical oxidation of alcohols: Simple derivatization strategy for their analysis by capillary electrophoresis

Strategies for capillary electrophoresis: Method development and validation for pharmaceutical and biological applications-Updated and completely revised edition

This review is in support of the development of selective, precise, fast, and validated capillary electrophoresis (CE) methods. It follows up a similar article from 1998, Wätzig H, Degenhardt M, Kunkel A. "Strategies for capillary electrophoresis: method development and validation for pharmaceutical and biological applications," pointing out which fundamentals are still valid and at the same time showing the enormous achievements in the last 25 years. The structures of both reviews are widely similar, in order to facilitate their simultaneous use. Focusing on pharmaceutical and biological applications, the successful use of CE is now demonstrated by more than 600 carefully selected references. Many of those are recent reviews; therefore, a significant overview about the field is provided. There are extra sections about sample pretreatment related to CE and microchip CE, and a completely revised section about method development for protein analytes and biomolecules in general. The general strategies for method development are summed up with regard to selectivity, efficiency, precision, analysis time, limit of detection, sample pretreatment requirements, and validation.

Sensitive Detection of Nitrite and Nitrate in Seawater by 222 nm UV-Irradiated Photochemical Conversion to Peroxynitrite and Ion Chromatography-Luminol Chemiluminescence System

Sensitive detection methods for nitrite (NO₂^-) and nitrate (NO₃^-) ions are essential to understand the nitrogen cycle and for environmental protection and public health. Herein, we report a detection method that combines ion-chromatographic separation of NO₂^- and NO₃^-, on-line photochemical conversion of these ions to peroxynitrite (ONOO^-) by irradiation with a 222 nm excimer lamp, and chemiluminescence from the reaction between luminol and ONOO^-. The detection limits for NO₂^- and NO₃^- were 0.01 and 0.03 μM, respectively, with linear ranges of 0.010-2.0 and 0.10-3.0 μM, respectively, at an injection volume of 1 μL. The results obtained by the proposed method for seawater analysis corresponded with those of a reference method (AutoAnalyzer based on the Griess reaction). As luminol chemiluminescence can measure ONOO^- at picomolar concentrations, our method is expected to be able to detect NO₂^- and NO₃^- at picomolar concentrations owing to the high conversion ratio to ONOO^- (>60%), assuming that contamination and background chemiluminescence issues can be resolved. This method has the potential to emerge as an innovative technology for NO₂^- and NO₃^- detection in various samples.

Capillary and microchip electrophoresis with contactless conductivity detection for analysis of foodstuffs and beverages

The paper provides a comprehensive survey of the use of capillary and microchip electrophoresis in combination with contactless conductivity detection (C⁴D) for the analysis of drinking water, beverages and foodstuffs. The introduction sets forth the fundamentals of conductivity detection anddescribes an axialC⁴Dversion. There is also a detailed discussion of the determination of inorganic ions, organic acids, fatty acids, amino acids, amines, carbohydrates, foreign substances and poisons from the standpoint of separation conditions, sample treatment and detection limits. Special attention is paid to the analysis of foodstuffs at microchips with emphasis on the employed material and connection of the microchip with the C⁴D. The review attempts to draw attention to modern trends, such as dual-opposite injection, field-enhanced sample injection, electromembrane extraction and on-line combination of microdialysis with CE. CE/C⁴D is characterised by high universality, high speed of analysis, simple sample preparation, small consumption of sample and other chemicals.

Capillary electromigration methods for food analysis and Foodomics: Advances and applications in the period February 2019-February 2021

This work presents a revision of the main applications of capillary electromigration methods in food analysis and Foodomics. Articles that were published during the period February 2019-February 2021 are included. The work shows the multiple CE methods that have been developed and applied to analyze different types of molecules in foods. Namely, CE methods have been applied to analyze amino acids, biogenic amines, carbohydrates, chiral compounds, contaminants, DNAs, food additives, heterocyclic amines, lipids, secondary metabolites, peptides, pesticides, phenols, pigments, polyphenols, proteins, residues, toxins, vitamins, small organic and inorganic compounds, as well as other minor compounds. The last results on the use of CE for monitoring food interactions and food processing, including recent microchips developments and new applications of CE in Foodomics, are discussed too. The new procedures of CE to investigate food quality and safety, nutritional value, storage and bioactivity are also included in the present review work.

Determination of the alcoholic content in whiskeys using micellar electrokinetic chromatography on microchips

This report describes the development of a methodology based on micellar electrokinetic chromatography for the separation of alcohols on chip-based systems aiming the determination of alcoholic content in whiskey samples. The separation conditions were optimized the best results were achieved using 50 mmolL^-1 phosphate buffer containing 30 mmolL^-1 sodium dodecyl sulfate. The alcoholic content was determined in 16 seized whiskey samples from 4 different brands as well as in the original samples. The methodology presented herein allowed the correct classification of 75% of the seized samples as adulterated and the data obtained did not statistically differ from those recorded by a reference technique. The proposed analytical approach emerges as a promising tool to provide a rapid screening of the beverages authenticity and it may be useful to be widely explored for the quality control.

Multistage Signals Based on Cyclic Chemiluminescence for Decoding Complex Samples

Identification of complex samples presents a difficult challenge for modern analytical techniques, and the differentiation among closely similar mixtures often remains indeterminate. In this article, we designed a simplified cyclic chemiluminescence (CCL) system that is able to measure multistage signals in a single sample injection. The system was used to investigate the CCL reactions of the binary, ternary, and multicomponent mixtures. Results showed that each mixture has a unique exponential decay equation (EDE) with a constant decay coefficient (k-value) to describe the change law of its multistage signals. Further studies found that different brands of liquor, beer, toner, and baby powder have different k-values, and the same brand of the commodities between different batches have the same k-values, which allows facile identification of these complex samples. We then used different catalysts to design digital codes of the k-value for further improving the identifying ability of CCL. Moreover, the multistage signals are like fingerprints and could be used for linear discriminate analysis, which provides another complementary approach for identification of complex samples. Finally, we demonstrated that CCL shows potential applications in certification and quality assurance according to the change of the k-values of the sample. This work demonstrates that excellent discrimination ability of CCL for the identification of complex samples and provides a promising technology for quality assurance.

CO2 reduction using paper-derived carbon electrodes modified with copper nanoparticles

The conversion of CO₂ into useful chemicals can lead to the production of carbon neutral fuels and reduce greenhouse gas emissions. A key technological challenge necessary to enable such a process is the development of substrates that are active, cost effective, and selective for this reaction. In this regard, the reduction of CO₂via electrochemical means is one of the most attractive alternatives but still requires rather unique electrodes. Considering the potential of this approach, this report describes a one-step methodology for the synthesis of carbon electrodes derived from simple paper and modified with various metallic nanoparticles. Upon a preliminary selection based on the catalytic activity towards CO₂ reduction, the electrodes containing CuNPs were further characterized by Raman spectroscopy, and electrical/electrochemical techniques. These electrodes were then applied for the electrochemical reduction of CO₂, leading to the formation of compounds with one carbon atom (formic acid), two carbon atoms (ethenone), three carbon atoms (propanoic acid) and four carbon atoms (butanol and butanoic acid).

Electrochemical reduction of CO₂ on paper-derived carbon electrodes modified with metallic nanoparticles.