13 Electrochemistry in Laboratory Flow Systems

Organic electrosynthesis in flow reactors is an area of increasing interest, with efficient mass transport and high electrode area to reactor volume present in many flow electrolysis cell designs facilitating higher rates of production with high selectivity. The controlled reaction environment available in flow cells also offers opportunities to develop new electrochemical processes. In this chapter, various types of electrochemical flow cells are reviewed in the context of laboratory synthesis, paying particular attention to how the different reactor environments impact upon the electrochemical processes, and the factors responsible for good cell performance. Coverage includes well-established plane-parallel-plate designs, reactors with small interelectrode gaps, extended-channel electrolysis cells, and highly sophisticated designs with rapidly rotating electrodes to enhance mass transport. In each case, illustrative electrosyntheses are presented.

Perspective—Insights into Solar-Rechargeable Redox Flow Cell Design: A Practical Perspective for Lab-Scale Experiments

Solar-rechargeable redox flow batteries (SRFBs) offer feasible solar energy storage with high flexibility in redox couples and storage capacity. Unlike traditional redox flow batteries, homemade flow cell reactors are commonly used in most solar-rechargeable redox flow batteries integrated with photoelectrochemical devices as it provides high system flexibility. This perspective article discusses current trends of the architectural and material characteristics of state-of-the-art photoelectrochemical flow cells for SRFB applications. Key design aspects and guidelines to build a photoelectrochemical flow cell, considering practical operating conditions, are proposed in this perspective.

Deep assessment of human disease-associated ribosomal RNA modifications using Nanopore direct RNA sequencing

The catalytically active component of ribosomes, rRNA, is long studied and heavily modified. However, little is known about functional and pathological consequences of changes in human rRNA modification status. Direct RNA sequencing on the Nanopore platform enables the direct assessment of rRNA modifications. We established a targeted Nanopore direct rRNA sequencing approach and applied it to CRISPR-Cas9 engineered HCT116 cells, lacking specific enzymatic activities required to establish defined rRNA base modifications. We analyzed these sequencing data along with wild type samples and in vitro transcribed reference sequences to specifically detect changes in modification status. We show for the first time that direct RNA-sequencing is feasible on smaller, i.e. Flongle, flow cells. Our targeted approach reduces RNA input requirements, making it accessible to the analysis of limited samples such as patient derived material. The analysis of rRNA modifications during cardiomyocyte differentiation of human induced pluripotent stem cells, and of heart biopsies from cardiomyopathy patients revealed altered modifications of specific sites, among them pseudouridine, 2-O-methylation of ribose and acetylation of cytidine. Targeted direct rRNA-seq analysis with JACUSA2 opens up the possibility to analyze dynamic changes in rRNA modifications in a wide range of biological and clinical samples.

Electrocatalysts derived from copper complexes transform CO into C2+ products effectively in a flow cell

The highest performance flow cells capable of electrolytically converting CO2 into higher value chemicals and fuels pass a concentrated hydroxide electrolyte across the cathode. A major problem for CO2 electrolysis is that this strongly alkaline medium converts the majority of CO2 into unreactive HCO3– and CO32– rather than CO2 reduction reaction (CO2RR) products. The electrolysis of CO (instead of CO2) does not suffer from this same problem because CO does not react with hydroxide. Moreover, CO can be more readily converted into products containing two or more carbon atoms (i.e., C2+ products). While several solid-state electrocatalysts have proven competent at converting CO into C2+ products, we demonstrate here that molecular electrocatalysts are also effective at mediating this transformation in a flow cell. Using a molecular copper phthalocyanine (CuPc) electrocatalyst, CO was electrolyzed into C2+ products at high rates of product formation (i.e., current densities J ≥200 mA/cm2), and at high Faradaic efficiencies for C2+ production (FEC2+; 72% at 200 mA/cm2). These findings present a new class of electrocatalysts for making carbon-neutral chemicals and fuels.

ONTbarcoder and MinION barcodes aid biodiversity discovery and identification by everyone, for everyone

Background DNA barcodes are a useful tool for discovering, understanding, and monitoring biodiversity which are critical tasks at a time of rapid biodiversity loss. However, widespread adoption of barcodes requires cost-effective and simple barcoding methods. We here present a workflow that satisfies these conditions. It was developed via “innovation through subtraction” and thus requires minimal lab equipment, can be learned within days, reduces the barcode sequencing cost to < 10 cents, and allows fast turnaround from specimen to sequence by using the portable MinION sequencer. Results We describe how tagged amplicons can be obtained and sequenced with the real-time MinION sequencer in many settings (field stations, biodiversity labs, citizen science labs, schools). We also provide amplicon coverage recommendations that are based on several runs of the latest generation of MinION flow cells (“R10.3”) which suggest that each run can generate barcodes for > 10,000 specimens. Next, we present a novel software, ONTbarcoder, which overcomes the bioinformatics challenges posed by MinION reads. The software is compatible with Windows 10, Macintosh, and Linux, has a graphical user interface (GUI), and can generate thousands of barcodes on a standard laptop within hours based on only two input files (FASTQ, demultiplexing file). We document that MinION barcodes are virtually identical to Sanger and Illumina barcodes for the same specimens (> 99.99%) and provide evidence that MinION flow cells and reads have improved rapidly since 2018. Conclusions We propose that barcoding with MinION is the way forward for government agencies, universities, museums, and schools because it combines low consumable and capital cost with scalability. Small projects can use the flow cell dongle (“Flongle”) while large projects can rely on MinION flow cells that can be stopped and re-used after collecting sufficient data for a given project.

Cocaine Detection by a Laser-Induced Immunofluorometric Biosensor

The trafficking of illegal drugs by criminal networks at borders, harbors, or airports is an increasing issue for public health as these routes ensure the main supply of illegal drugs. The prevention of drug smuggling, including the installation of scanners and other analytical devices to detect small traces of drugs within a reasonable time frame, remains a challenge. The presented immunosensor is based on a monolithic affinity column with a large excess of immobilized hapten, which traps fluorescently labeled antibodies as long as the analyte cocaine is absent. In the presence of the drug, some binding sites of the antibody will be blocked, which leads to an immediate breakthrough of the labeled protein, detectable by highly sensitive laser-induced fluorescence with the help of a Peltier-cooled complementary metal-oxide-semiconductor (CMOS) camera. Liquid handling is performed with high-precision syringe pumps and microfluidic chip-based mixing devices and flow cells. The biosensor achieved limits of detection of 7 ppt (23 pM) of cocaine with a response time of 90 s and a total assay time below 3 min. With surface wipe sampling, the biosensor was able to detect 300 pg of cocaine. This immunosensor belongs to the most sensitive and fastest detectors for cocaine and offers near-continuous analyte measurement.