<p><strong>Development of a portable, distance-based paper analytical sensor <br />for carbonate detection.</strong></p> <p> </p> <p><strong>Zakia Tebetyo<sup>1</sup>, Samantha Richardson<sup>1</sup>,</strong> <strong>Leigh Madden<sup>2</sup>,</strong> <strong>Mark Lorch<sup>1</sup>, Nicole Pamme<sup>1,3</sup></strong></p> <p><em><sup>1</sup></em><em>School<sup> </sup>of Natural Sciences, University of Hull. </em></p> <p><em><sup>2 </sup></em><em>Centre for Biomedicine, Hull York Medical School, University of Hull, UK</em></p> <p><em><sup>3</sup></em><em>Department of Materials and Environmental Chemistry, Stockholm University, Sweden</em></p> <p>In this study we transferred a laboratory-based titration reaction for carbonate determination onto a portable paper-based analytical device (PAD). The carbonate quantity can be read out by measuring the distance of a colour change along a paper-based reaction channel. Device dimensions and detection reagent constituents were optimized to enable detection of carbonate ions in the range of 0 – 1000 mg L<sup>-1</sup>. The PAD featured a reaction channel in hydrophilic filter paper defined by a hydrophobic wax barrier. The detection reagent consisted of citric acid/citrate buffer (0.5 M, pH 2.5), bromocresol green (BCG) indicator (0.10% w/v) and PDADMAC (5.0 % v/v) dissolved in 20% ethanol. The base of the device was sealed with tape to prevent reagents leaking. Sixty microlitres of carbonate sample were added to the base of the channel and the liquid was allowed to wick up the channel. Colour development occurred as the carbonate ions reacted with the hydronium ions in the detection reagent resulting in a colour change of the BCG indicator from yellow to blue.</p> <p>To optimise the reaction channel, two dimensions were compared, 1 mm x 30 mm and 2 mm x 30 mm. The device with the wider channel gave a higher colour intensity between carbonate concentrations 0 – 200 mg L<sup>-1</sup>. In this range the sensor gave a linear response. The effect of filter paper pore size was investigated to study wicking time. Whatman 4 paper (pore size 23 µm) had a six times faster wicking rate of 7 min compared to Whatman 1 (11 µm) with 42 min. Reproducibility studies (100, 200, 400, 500, 600, 800 and 1000 ppm carbonate, n = 6) gave a maximum RSD of 2.4% showing consistency across the range of samples tested. Interference tests were conducted with 500 ppm  with additional environmentally occurring ions, i.e. 250 ppm , 250 ppm  or 50 ppm of  (F=1.924<Fcrit=3.411, no significant difference). There was no significant interference found from these ions.</p> <p>Future work will focus on packaging and sealing the devices for on-site use, benchmarking with real environmental samples and in-the-field use with by minimally trained personnel.</p>

Keywords: preconcentration, heavy metal, cafetiere, citizen science, paper-based microfluidics Heavy-metal analysis of water samples using microfluidics paper-based analytical devices (µPAD) with colourimetric readout is of great interest due to its simplicity, affordability and potential for Citizen Science-based data collection [1]. However, this approach is limited by the relatively poor sensitivity of the colourimetric substrates, typically achieving detection within the mg L-1 range, whereas heavy-metals exist in the environment at <μg L-1 quantities [2]. Preconcentration is commonly used when analyte concentration is below the analytical range, but this typically requires laboratory equipment and expert users [3]. Here, we are developing a simple method for pre-concentration of heavy metals, to be integrated with a µPAD workflow that would allow Citizen Scientists to carry out pre-concentration as well as readout on-site. The filter mesh from an off-the-shelf cafetière (350 mL) was replaced with a custom-made bead carrier basket, laser cut in PMMA sheet featuring >500 evenly spread 100 µm diameter holes. This allowed the water sample to pass through the basket and mix efficiently with the 2.6 g ion-exchange resin beads housed within (Lewatit® TP207, Ambersep® M4195, Lewatit® MonoPlus SP 112). An aqueous Ni2+ sample (0.3 mg L-1, 300 mL) was placed in the cafetiere and the basket containing ion exchange material was moved up and down for 5 min to allow Ni2+ adsorption onto the resin. Initial investigations into elution with a safe, non-toxic eluent focused on using NaCl (5 M). These were carried out by placing the elution solution into a shallow dish and into which the the resin containing carrier basket was submerging. UV/vis spectroscopy via a colourimetric reaction with nioxime was used to monitor Ni2+ absorption and elution. After 5 min of mixing it was found that Lewatit® TP207 and Ambersep® M4195 resins adsorbed up to 90% of the Ni2+ ions present in solution and the Lewatit® MonoPlus SP 112 adsorbed up to 60%. However, the Lewatit® MonoPlus SP 112 resin performed better for elution with NaCl. Initial studies showed up to 30% of the Ni2+ was eluted within only 1 min of mixing with 10 mL 5 M NaCl. Using a cafetière as pre-concentration vessel coupled with non-hazardous reagents in the pre-concentration process allows involvement of citizen scientists in more advanced environmental monitoring activities that cannot be achieved with a simple paper-based sensor alone. Future work will investigate the user-friendliness of the design by trialling the system with volunteers and will aim to further improve the trapping and elution efficiencies. References: * Almeida, M., et al., Talanta, 2018, 177, 176-190. * Lace, A., J. Cleary, Chemosens., 2021. 9, 60. * Alahmad, W., et al.. Biosens. Bioelectron., 2021. 194, 113574.

Sporopollenin exine capsules (SpECs) are microcapsules derived from the outer shells (exines) of plant spore and pollen grains. This work reports the first clinical study on healthy volunteers to show enhanced bioavailability of vitamin D encapsulated in SpECs from Lycopodium clavatum L. spore grains vs vitamin D alone, and the first evidence (in vitro, ex vivo and in vivo) of mechanisms to account for the enhancement and release of the active in the small intestine. Evidence for mucoadhesion of the SpECs contributing to the mechanism of the enhancement is based on: (i) release profile over time of vitamin D in a double blind cross-over human study showing significant release in the small intestine; (ii) in vivo particle counting data in rat showing preferred retention of SpECs vs synthetic beads; (iii) ex vivo99mTc labelling and counting data using rat small intestine sections showing preferred retention of SpECs vs synthetic beads; (iv) in vitro mucoadhesion data. Triggered release by bile in the small intestine was shown in vitro using solid state NMR and HPLC.

This chapter discusses some simpler but no less important molecules: water, lipids, carbohydrates, and nucleotides. These molecules form the physical structures that bound cells and the medium in which the very chemistry of life takes place. Water’s structure and composition allows it to participate makes it a polar molecule and an astonishingly good solvent. Meanwhile, lipids play three main roles in biochemistry: energy storage, signalling, and structure formation. Finally, carbohydrates provide the fuel that powers cells; they form the scaffolding around which so many structures are built; and they frequently embellish proteins, modifying their behaviours or adding functionality.

Routine monitoring of available soil nutrients is required to better manage agricultural land1, especially in many lower and middle income countries (LMICs). Analysis often still relies on laboratory-based equipment, meaning regular monitoring is challenging.2 The limited number of in situ sensors that exist are expensive or have complex workflows, thus are not suitable in LMICs, where the need is greatest.3 We aim to develop a simple-to-use, low-cost analysis system that enable farmers to directly monitor available nutrients and pH on-site, thus making informed decisions about when and where to apply fertilisers. We combine nutrient extraction via a cafetiere-based filtration system with nutrient readout on a paper microfluidic analysis device (PAD) employing colour producing reactions that can be captured via a smartphone camera through an app. Image analysis of colour intensity permits quantitation of analytes. We initially focus on key nutrients (phosphate, nitrate) and pH analysis. For extraction of phosphate, we mixed soil and water in the cafetiere and quantified the extracted phosphate via phosphomolybdenum blue chemistry. For example, for 5 g of soil, a water volume of about 160 mL led to optimum extraction. Active mixing, by pushing coffee filter plunger up and down, aided extraction. A mixing period of 3 min yielded maximum extraction; this time period was deemed suitable for an on-site workflow. Following nutrient extraction, a simple-to-use readout system is required. For this, we developed colourimetric paper-based microfluidic devices; these are simply dipped into the decanted soil supernatant from the cafetiere and wick fluids based on capillary forces. Chemical reagents are pre-stored in reaction zones, created by patterning cellulose with wax barriers. Our devices contain multiple paper layers with different reagents; these are folded, laminated and holes cut for sample entry. Following the required incubation time, the developed colour is captured using a smartphone. This constitutes a portable detector, already available to envisaged end users, even in LMICs. We have previously developed an on-paper reaction for monitoring phosphates in fresh water in the mg L-1 working range, with readout after an incubation period of 3 min. This method was adapted here to enable storage at ambient temperatures up to 1 week by incorporating additional acidic reagents. Further pad devices were developed in our group for colour-based readout of nitrate, involving a two-step reaction chemistry. Within a relatively short incubation period (≤8 min) a pink coloured was formed following reduction of nitrate to nitrite with zinc and subsequent reaction to form an azo-dye. This system achieved detection in the low mg L-1 range. Moreover, a pad to monitor pH was developed, employing chlorophenol red indicator, with linear response achieved over the relevant pH 5-7 range. Our analysis workflow combines a simple-to-use cafetiere-based extraction method with paper microfluidic colour readout and smart-phone detector. This has the potential to enable farmers to monitor nutrients in soils on-site. Future work will aim at integrating multiple analytes into a single analysis card and to automate image analysis. [1] Europ. J. Agronomy, 55, 42–52, 2014. [2] Nutr. Cycling Agroecosyst., 109, 77-102, 2017. [3] Sens Actuators B, 30, 126855, 2019.

We demonstrate how a combination of paper microfluidic devices and handheld mobile technology can be used by citizen scientists to carry out a sustained water monitoring campaign. We have developed a paper-based analysis device and a 3 minute sampling workflow that requires no more than a container, a test device and a smartphone app. The contaminant measured in these pilots are phosphates, detectable down to 3 mg L -1 . Together these allow volunteers to successfully carry out cost-effective, high frequency, phosphate monitoring over an extended geographies and periods.

Monitoring water quality traditionally involves experts collecting samples for laboratory-based analysis; a time consuming, costly process.1 It has been recognised that frequent measurements are needed to understand patterns and pressures of changing contaminant concentrations.2 One approach empowers citizens with simple tools, enabling them to monitor water quality regularly.3 Generally, citizen-led sampling has involved volunteers collecting samples for later analysis by experts. We describe an approach comprising of a series of paper-based sensors, that when coupled with a smartphone, enable citizens to participate in simultaneous collection of samples and generation of onsite measurements. We developed paper microfluidic analytical devices (PADs) for the detection of contaminants (nutrients, metals, organics). All devices were designed to be simple to use with rapid colour readout achieved with minimal user input. Filter paper was patterned with hydrophobic wax barriers to create reaction zones. Within these zones, chemical reagents were stored, that would, upon sample addition, change colour proportionally to the analyte concentration. After addition and drying of reagents, devices were sealed by lamination with a hole cut to allow for sample entry. For water analysis, the devices were placed directly onto the water sample and incubated for a short time (< 10 min). The coloured reaction products were visible to the naked eye; more precise quantification was achieved by capturing a digital image followed by colour intensity analysis. We adapted spectroscopic determination chemistry, so that it was suitable for use on a portable paper platform; successfully developing separate devices for phosphate (LOD 3 mg L-1), copper (LOD 2 mg L-1), chromium (LOD 0.5 mg L-1), nickel (LOD 3 mg L-1), and triclosan (LOD 3 mg L-1). To detect very low concentrations (>µg L-1) of contaminants (metals, organics) usually found in the environment, we aim to combine the simple paper-based readout with an in-field pre-concentration step. By incorporating an electrospun membrane with a simple filtration system, adsorption of copper ions on the membrane surface was demonstrated. Coupling such a pre-concentration method with colour-generating paper readout devices, would potentially provide a simple means for on-site monitoring at environmentally relevant levels. Citizen-led sampling was undertaken to monitor phosphates in freshwater across the Humber region (UK), Belgium, Germany and the Netherlands. Devices featured six reaction zones, two control zones and internal calibration (coloured squares). Results were captured using a custom-developed app, RiverDIP (Natural Apptitude) that also recorded location, turbidity (photos), GPS, date, time and waterbody. Submitted data were analysed, and subsequently plotted on an online map, allowing volunteers to see all sampling efforts with > 300 results returned so far. Engagement with volunteers was investigated to empower people by informing them of sources of domestic pollution. In summary, we have developed a series of simple-to-use paper-based devices to detect water contaminants and demonstrated the feasibility of citizen-led sampling to monitor water quality. Future work will involve further development towards a system for simple onsite pre-concentration and monitoring of heavy metals involving volunteers in the sampling process. * 1.J. Environ. Manage.,87 2008, 639-648. * 2.Sens., 5, 2005, 4-37. * 3.Front. Ecol. Environ.,10, 2012, 298-304.

Contamination of waterways is of increasing concern, with recent studies demonstrating elevated levels of antibiotics, antidepressants, household, agricultural and industrial chemicals in freshwater systems. Thus, there is a growing demand for methods to rapidly and conveniently monitor contaminants in waterways. Here we demonstrate how a combination of paper microfluidic devices and handheld mobile technology can be used by citizen scientists to carry out a sustained water monitoring campaign. We have developed a paper-based analytical device and a 3 minute sampling workflow that requires no more than a container, a test device and a smartphone app. The contaminant measured in these pilots are phosphates, detectable down to 3 mg L-1. Together these allow volunteers to successfully carry out cost-effective, high frequency, phosphate monitoring over an extended geographies and periods.

Biochemistry: A Very Short Introduction discusses the key concepts of biochemistry, as well as the historical figures in the field and the molecules they studied. From bacteria to humans, all living things are composed of cells of one type or another, all of which have fundamentally the same chemistry. Biochemistry is the study of the chemical reactions within these cells; the molecules that are created, manipulated, and destroyed as a result of them; and the chemical structures such as DNA on which these biochemical reactions take place. This VSI considers the current science and innovations in the field. It also looks at the interaction between biochemistry, biotechnology, and synthetic biology.

In this study, we assess the influence of solvation on the accuracy and reliability of isotropic nuclear magnetic shielding calculations for amino acids in comparison to experimental data. We focus particularly on the performance of solvation methods for different protonation states, as biological molecules occur almost exclusively in aqueous solution and are subject to protonation with pH. We identify significant shortcomings of current implicit solvent models and present a hybrid solvation approach that improves agreement with experimental data by taking into account the presence of direct interactions between amino acid protonation state and water molecules.

Gases, liquids and solids are not the only possibilities for states of matter, they aren't even the most common states. Plasma, from which stars are made, is much more dominant. The tremendous temperatures inside stars rips electrons from atoms forming gas-like plasma. What's more, there are many other states with exotic names like Fermionic condensates, superfluids and quantum spin liquids, which occur under a wealth of extreme conditions. Others states are commonplace in the world we inhabit and liquid crystals are one of them. This chapter takes a look at this odd state of matter and how it led to light emitting devices dominating our digital age.