Current Analytical Chemistry - Volume 15, Issue 7, 2019

Background: Designing an analytical methodology for complicated matrices, such as biological and environmental samples, is difficult since the sample preparation procedure is the most demanding step affecting the whole analytical process. Nowadays, this step has become more challenging by the legislations and environmental concerns since it is a prerequisite to eliminate or minimize the use of hazardous substances in traditional procedures by replacing with green techniques suitable for the sample matrix. Methods: In addition to the matrix, the nature of the analyte also influence the ease of creating green analytical techniques. Recent developments in the chemical analysis provide us new methodologies introducing microextraction techniques and among them, solid phase microextraction (SPME) has emerged as a simple, fast, low cost, reliable and portable sample preparation technique that minimizes solvent consumption. Results: The use of home-made fibers is popular in the last two decades since the selectivity can be tuned by changing the surface characteristics through chemical and electrochemical modifications. Latter technique is preferred since the electroactive polymers can be coated onto the fiber under controlled electrochemical conditions and the film thicknesses can be adjusted by simply changing the deposition parameters. Thermal resistance and mechanical strength can be readily increased by incorporating different dopant ions into the polymeric structure and selectivity can be tuned by inserting functional groups and nanostructures. A vast number of analytes with wide range of polarities extracted by this means can be determined with a suitable chromatographic detector coupled to the system. Therefore, the main task is to improve the physicochemical properties of the fiber along with the extraction efficiency and selectivity towards the various analytes by adjusting the electrochemical preparation conditions. Conclusion: This review covers the fine tuning conditions practiced in electrochemical preparation of SPME fibers and in-tube systems and their applications in environmental, food and clinical analysis.

Background: Recently, in all fields of analytical chemistry, increased attention has been paid to extraction procedures and instrumental methods, which are easily scalable and are able to automate in order to improve the “high-throughput” capability. Introduction: The main goal of these applications relates to an improvement of the precision in the quantitative analysis, reduction of different sources of errors, decrease the analysis time and, in general, improve the analytical performances. Often these points can be in contrast to each other, not allowing to achieve the expected result but forcing a compromise between the objectives of the method and the analytical performance. Methods: In this review, following the evolution of the (micro)extraction procedures and instrument configurations, the recent procedures used in bioanalytical chemistry are critically evaluated. The aim of this paper is providing an overview of the approaches available in order to perform on-line coupling of various extraction techniques with chromatographic methods for the analysis of different compounds in various samples. Furthermore, a comparison between off-line and on-line systems, advantages of on-line systems applied on major extractive techniques and future perspectives are described. Result: The extraction methods suitable for on-line coupling covered in this review are: liquid-liquid extraction (LLE), solid phase extraction (SPE), solid phase microextraction (SPME), dispersive liquid- liquid microextraction (DLLME), microextraction by packed sorbent (MEPS), supercritical fluid extraction (SFE) and fabric phase sorptive extraction (FPSE). Conclusion: An overview of the micro-extraction techniques mentioned above was provided, making a comparison between them and focusing attention on future perspectives.

Background: Green chemistry is the application of methodologies and techniques to reduce the use of hazardous substances, minimize waste generation and apply benign and cheap applications. Methods: In this article, the following issues were considered: greener solvents and reagents, miniaturization of analytical instrumentation, reagent-free methodologies, greening with automation, greener sample preparation methods, and greener detection systems. Moreover, the tables along with the investigated topics including environmental analysis were included. The future aspects and the challenges in green analytical chemistry were also discussed. Results: The prevention of waste generation, atomic economy, use of less hazardous materials for chemical synthesis and design, use of safer solvents, auxiliaries and renewable raw materials, reduction of unnecessary derivatization, design degradation products, prevention of accidents and development of real-time analytical methods are important for the development of greener methodologies. Conclusion: Efforts should also be given for the evaluation of novel solid phases, new solvents, and sustainable reagents to reduce the risks associated with the environment. Moreover, greener methodologies enable energy efficient, safe and faster that reduce the use of reagents, solvents and preservatives which are hazardous to both environment and human health.

Automated post-column sample manipulation is undoubtedly one of the most challenging approaches in liquid chromatography for the improvement of method selectivity and sensitivity. With the post-column analyte derivatization being the most-abundant approach approach of this category, other strategies typically comprise post-column infusion of internal standard or other reagents prior to mass spectrometric detection to enhance the ionization efficiency of the analyte or to compensate the ion suppression/enhancement. In this review, on-line post column methodologies focused on the quality control of pharmaceuticals and biomedical applications will be presented and discussed. Emphasis will be given on the automation capabilities of such systems.

Background: For more than a decade, Energy Dispersive X-Ray Fluorescence (EDXRF) spectrometry is the primary analytical technique in archaeometric research and especially in the study of ancient copper artefacts. EDXRF has established itself as the fundamental archaeometric analytical technique because of features like: the ability to analyze samples in a non destructive or non invasive way, no requirements for sample preparation, portability, in situ analysis, simultaneous determination of many elements and finally its easy in use. At the same time there is an explosion of related research publications which provide new possibilities to museums and archaeology scientists. On the other hand, due to its limitations it cannot provide information for every analytical question. Objective: The goal of this article is to present an overview of the capabilities of the contemporary EDXRF spectrometry for the study of ancient copper artifacts and the necessity to be implemented, depending on the analytical question, in correlation with complementary analytical techniques which are presented through related case studies. Conclusion: The demand for studying artefacts in situ, the evolution of the instrumentation and the access of more scientists (historians, archaeologists, curators etc.) to archaeometry will maintain EDXRF spectrometry as the central analytical technique. Limitations like inability for light elements detection, penetration depth, low (relatively) sensitivity can be partially overcome with the implementation of other analytical techniques which will provide complementary information. Moreover, progress in non-invasive analysis and new portable instruments combining elemental and molecular techniques expand significantly the capabilities of in situ analysis.

Background: The sample preparation is the most crucial step in the analytical method development. Taking this into account, it is easily understood why the domain of sample preparation prior to detection is rapidly developing. Following the modern trends towards the automation, miniaturization, simplification and minimization of organic solvents and sample volumes, green microextraction techniques witness rapid growth in the field of food quality and safety. In a globalized market, it is essential to face the consumers need and develop analytical methods that guarantee the quality of food products and beverages. The strive for the accurate determination of organic hazards in a famous and appreciated alcoholic beverage like wine has necessitated the development of microextraction techniques. Objective: The objective of this review is to summarize all the recent microextraction methodologies, including solid phase extraction (SPE), solid phase microextraction (SPME), liquid-phase microextraction (LPME), dispersive liquid-liquid microextraction (DLLME), stir bar sorptive extraction (SBSE), matrix solid-phase dispersion (MSPD), single-drop microextraction (SDME) and dispersive solid phase extraction (DSPE) that were developed for the determination of hazardous organic compounds (pesticides, mycotoxins, colorants, biogenic amines, off-flavors) in wine. The analytical performance of the techniques is evaluated and their advantages and limitations are discussed. Conclusion: An extensive investigation of these techniques remains vital through the development of novel strategies and the implication of new materials that could upgrade the selectivity for the extraction of target analytes.