Flow chemistry vs. flow analysis

A miniaturized flow batch chemical vapor generation system for Hg determination in fish by ICP-MS

A new flow batch (FB) system for chemical vapor generation (CVG) is proposed for mercury (Hg) determination in fish. An inductively coupled plasma mass spectrometer was used as a detector. Low-cost peristaltic mini pumps were used to propel the solutions and different configurations of FB systems (reactor/gas/liquid separator) were studied. The proposed configuration of the FB-CVG system allows good sensitivity, low limit of detection (LOD) and low consumption of reagents and sample solutions. In summary, only 1 mL of reductant, 1 mL of acid and 0.16 mL of sample are needed. The proposed method has good linearity, precision (better than 5 %), LOD of 0.008 μg g-1 and LOQ of 0.012 μg g-1, and high sample throughput, allowing 90 measurements/h. The accuracy of the method was evaluated through the analysis of a certified reference material (DOLT-4 Dogfish Liver), whose result is in good agreement with certified value (t-test with 95 % confidence level) and the quantification limit meets current legislations, of 1.0 μg g-1 (Brazil) and 0.3 μg g-1 (EU). In addition, analyte recovery test was done, where Hg recovery was better than 95 %, demonstrating the good analytical performance of the method. To demonstrate the applicability of the method, five samples of fish tissue (muscle) were analyzed. The proposed FB-CVG system, in addition to being low cost, is robust and requires only the volume of reagents necessary for Hg vapor generation, producing a very low amount of waste. It can be concluded that the proposed system can be used for routine analysis for Hg determination in fish tissue. It is worth noting that with the appropriate adjustments, the system can be coupled to different Hg detectors.

An Automated Hydrodynamically Mediated Technique for Preparation of Calibration Solutions via Capillary Electrophoresis System as a Promising Alternative to Manual Pipetting

In this paper, a novel procedure for preparing calibration solutions for capillary electrophoresis (CE)-based quantitative analysis is proposed. Our approach, named the automated hydrodynamically mediated technique (AHMT), uses a capillary and a pressure system to deliver the expected amount of working solution and diluent directly to a sample vial. As a result, calibration solutions are prepared automatically inside the CE instrument, without any or with minimal manual operation. Two different modes were tested: forward and reverse, differing in the direction of hydrodynamic flow. The calibration curves obtained for a model mixture of analytes using AHMT were thorough compared to the standard procedure based on manual pipetting. The results were consistent, though the volume of obtained calibration solutions and the potential risk of random errors were significantly minimized by AHMT. Its effectiveness was further enhanced by the application of SCIEX^® nanoVials, reducing the actual volume of calibration solutions down to 10 μL.

Flow Chemistry in Contemporary Chemical Sciences: A Real Variety of Its Applications

Flow chemistry is an area of contemporary chemistry exploiting the hydrodynamic conditions of flowing liquids to provide particular environments for chemical reactions. These particular conditions of enhanced and strictly regulated transport of reagents, improved interface contacts, intensification of heat transfer, and safe operation with hazardous chemicals can be utilized in chemical synthesis, both for mechanization and automation of analytical procedures, and for the investigation of the kinetics of ultrafast reactions. Such methods are developed for more than half a century. In the field of chemical synthesis, they are used mostly in pharmaceutical chemistry for efficient syntheses of small amounts of active substances. In analytical chemistry, flow measuring systems are designed for environmental applications and industrial monitoring, as well as medical and pharmaceutical analysis, providing essential enhancement of the yield of analyses and precision of analytical determinations. The main concept of this review is to show the overlapping of development trends in the design of instrumentation and various ways of the utilization of specificity of chemical operations under flow conditions, especially for synthetic and analytical purposes, with a simultaneous presentation of the still rather limited correspondence between these two main areas of flow chemistry.

Recent advances in continuous-flow organocatalysis for process intensification

The progresses on continuous-flow organocatalysis from 2016 to early 2020 are reviewed with focus on transition from batch to flow.

Electrochemical Biosensors as Potential Diagnostic Devices for Autoimmune Diseases

An important class of biosensors is immunosensors, affinity biosensors that are based on the specific interaction between antibodies and antigens. They are classified in four classes based on the type of employed transducer: electrochemical, optical, microgravimetric, and thermometric and depending on the type of recognition elements, antibodies, aptamers, microRNAs and recently peptides are integrating parts. Those analytical devices are able to detect peptides, antibodies and proteins in various sample matrices, without many steps of sample pretreatment. Their high sensitivity, low cost and the easy integration in point of care devices assuring portability are attracting features that justify the increasing interest in their development. The use of nanomaterials, simultaneous multianalyte detection and integration on platforms to form point-of-care devices are promising tools that can be used in clinical analysis for early diagnosis and therapy monitoring in several pathologies. Taking into account the growing incidence of autoimmune disease and the importance of early diagnosis, electrochemical biosensors could represent a viable alternative to currently used diagnosis methods. Some relevant examples of electrochemical assays for autoimmune disease diagnosis developed in the last several years based on antigens, antibodies and peptides as receptors were gathered and will be discussed further.

Synthesis of 1,2,5-oxathiazole-S-oxides by 1,3-dipolar cycloadditions of nitrile oxides to α-oxo sulfines

The generation of novel 1,2,5-oxathiazole-S-oxide cycloadducts from cycloaddition of nitrile oxide dipoles with α-oxo sulfines generated in situ from α-diazosulfoxides is reported.

Electrochemical immunosensors - A powerful tool for analytical applications

Immunosensors are biosensors based on interactions between an antibody and antigen on a transducer surface. Either antibody or antigen can be the species immobilized on the transducer to detect antigen or antibody, respectively. Because of the strong binding forces between these biomolecules, immunosensors present high selectivity and very high sensitivity, making them very attractive for many applications in different science fields. Electrochemical immunosensors explore measurements of an electrical signal produced on an electrochemical transductor. This signal can be voltammetric, potentiometric, conductometric or impedimetric. Immunosensors utilizing electrochemical detection have been explored in several analyses since they are specific, simple, portable, and generally disposable and can carry out in situ or automated detection. This review addresses the potential of immunosensors destined for application in food and environmental analysis, and cancer biomarker diagnosis. Emphasis is given to the approaches that have been used for construction of electrochemical immunosensors. Additionally, the fundamentals of immunosensors, technology of transducers and nanomaterials and a general overview of the possible applications of electrochemical immunosensors to the food, environmental and diseases analysis fields are described.

Liquid Beam Desorption Mass Spectrometry for the Investigation of Continuous Flow Reactions in Microfluidic Chips

In this work, we present the combination of microfluidic chips and mass spectrometry employing laser-induced liquid beam ionization/desorption. The developed system was evaluated with respect to stable beam generation and laser parameters as well as solvent compatibility. The device was exemplarily applied to study a vinylogous Mannich reaction performed in continuous flow on chip. Fast processes can be observed with this technique which in the future could be beneficial for studying intermediates or contribute to the elucidation of reaction mechanisms.

Enantioselective reaction monitoring utilizing two-dimensional heart-cut liquid chromatography on an integrated microfluidic chip

Chip-integrated, two-dimensional high performance liquid chromatography is introduced to monitor enantioselective continuous micro-flow synthesis. The herein described development of the first two-dimensional HPLC-chip was realized by the integration of two different columns packed with reversed-phase and chiral stationary phase material on a microfluidic glass chip, coupled to mass spectrometry. Directed steering of the micro-flows at the joining transfer cross enabled a heart-cut operation mode to transfer the chiral compound of interest from the first to the second chromatographic dimension. This allows for an interference-free determination of the enantiomeric excess by seamless hyphenation to electrospray mass spectrometry. The application for rapid reaction optimization at micro-flow conditions is exemplarily shown for the asymmetric organocatalytic continuous micro-flow synthesis of warfarin.

Applications of Continuous-Flow Photochemistry in Organic Synthesis, Material Science, and Water Treatment

Continuous-flow photochemistry in microreactors receives a lot of attention from researchers in academia and industry as this technology provides reduced reaction times, higher selectivities, straightforward scalability, and the possibility to safely use hazardous intermediates and gaseous reactants. In this review, an up-to-date overview is given of photochemical transformations in continuous-flow reactors, including applications in organic synthesis, material science, and water treatment. In addition, the advantages of continuous-flow photochemistry are pointed out and a thorough comparison with batch processing is presented.

Recent advances in flow injection analysis

A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis.