Electrokinetic extraction (EKE), coupled with polymer inclusion membranes (PIMs) for colourimetric detection, offers a promising approach for extracting metal ions from solid matrices, such as sand, without sample pretreatment. Our EKE system consists of a formic acid gel positioned at the cathode side to neutralise hydroxide ions generated by electrolysis during the EKE of Cu(II), whereas the anode side contains the sample compartment, prepared from a syringe tube into which the sample is placed. The PIM is sandwiched between these compartments to accumulate Cu(II) via EKE through the sand and into the PIM within which it complexes with a colour-forming reagent, 1-(2-pyridylazo)-2-naphthol (PAN), enabling quantification via colourimetric analysis. The system has been optimised to expand the quantification range of Cu(II), thus allowing greater applicability to a wider range of samples with different levels of heavy metals. Increasing the column diameter extended the upper limit of the quantification range from 7.5 mg kg-1 (4.5 mm column diameter) to 30.0 mg kg-1 (13.5 mm column diameter). Concurrently, optimisation of the PIM composition, containing 43.3 wt% cellulose triacetate (CTA)-56.0 wt% di-(2-ethylhexyl) phosphoric acid (D2EHPA)-0.8 wt% PAN, enhanced the overall recovery of Cu(II) from 64% ± 7% to 90% ± 4%. Overall, the optimised system has achieved a quantification range of 2.8-30.0 mg kg-1 of Cu(II), with an LOD of 0.9 and LOQ of 2.8 mg kg-1 of Cu(II).

Capillary electrophoresis (CE) is increasingly used in distributed field environmental monitoring, teaching, and citizen science. Consequently, the development of low-cost CE instruments using inexpensive components and do-it-yourself approaches has gained significant attention. Peristaltic micro-pumps (PMPs), with dimensions as small as 15 × 17 × 34 mm3, offer advantages such as low cost, compact size, and energy efficiency, making them highly suitable for miniaturized CE instruments with automated flow-through injection. This study presents the development and application of a closed-loop PMP integrated into a CE system to enhance flow-through injection precision and analytical performance. The closed-loop control design incorporates a Hall sensor to monitor pump rotor positions, ensuring stable operation. The modified PMP achieved a pressure relative standard deviation (RSD) of 0.7 % (n = 10), representing a threefold improvement over time-based and back electromotive force feedback controls. The system was applied to detect common cations and anions in drinking water. Experimental validation confirmed the reliability and precision of the CE system, with injection RSDs below 4.0 % (n = 42 for anions and 58 for cations). The calibration ranges were 0-500 μM with R2 values ≥ 0.994. Detection limits ranged from 0.9 to 3.6 μM. The RSDs (n = 10) of peak heights for ions in tap water were between 1.1 % and 7.7 %. Additionally, the CE system was employed to analyze total nitrogen and total phosphorus in water following persulfate oxidation. The total cost of the system was estimated to be approximately 6000 USD, including a ∼4000 USD TraceDec contactless conductivity detector. These findings demonstrate that the modified CE system with a closed-loop PMP significantly enhances injection precision, analytical performance, and versatility for environmental ion and nutrient detection. This system provides a reliable and cost-effective tool for on-site water quality monitoring.

Investigating astrocyte–neuron communication in the absence of neuron-to-neuron signalling is not feasible using traditional cell culture, due to the complexity of synaptic networks. To overcome this limitation, we developed a three-compartment microfluidic co-culture device that fluidically isolates two neuronal populations while allowing astrocyte growth throughout. This design enables investigation of astrocyte-specific contributions to neuropathology between synaptically isolated neurons. The device features 10 banks forming maze-like structures that physically and fluidically isolate two primary cortical neuron populations by restricting neurite extension and fluid exchange, while enabling an astrocyte monolayer to infiltrate all compartments. Using this platform, we treated one neuron–astrocyte population with the excitotoxin kainic acid (KA) and observed neurite degeneration in the adjacent, fluidically isolated neuronal population, connected via astrocytes. Pre-treatment of the astrocyte-only compartment with the membrane-permeable calcium chelator BAPTA-AM significantly reduced neurotoxicity in the isolated neurons. These findings indicate a calcium-dependent role for astrocytes in mediating excitotoxic pathology between physically segregated neuronal populations. This is the first platform to construct a neuronal network with directional connectivity between different populations of neurons and astrocytes and enables us to uncouple and independently investigate the role of astrocytes in the temporal and spatial events of neuronal network activity.

Microplastics (MPs) have become a critical environmental issue due to their persistence, widespread presence and potential biological effects. With the growing global consumption of bottled water, this product has recently come under scrutiny as a significant source of MPs contamination for humans. To assess the MPs exposure in the Malaysian population through bottled water consumption, eight commonly available bottled water brands were analysed in triplicate (n = 3) using an advanced, rapid and precise MPs identification technique - Laser Direct Infrared (LDIR) chemical imaging spectroscopy. This study presents the first application of LDIR spectroscopy for the detection and quantification of MPs in bottled water in Malaysia, contributing novel regional data for Southeast Asia. An average of 1421.20 +/- 915.70 particles/L was detected, with most particles measuring under 50 mu m. Fifteen particle types were identified, primarily natural polyamide, cellulose, chitin, rubber, polyamide (PA) and polyethylene terephthalate (PET). Remarkably, nine out of the EU's ten priority MPs were identified, with an average concentration of 28.14 MPs/L and a mean weight of 2.85 mu g/L, most of which were under 30 mu m in size. Priority MPs such as PA, PET, polyethylene (PE), polypropylene (PP) and polyurethane (PU) were also frequently observed. Although bottled water may contribute less MPs exposure compared to other sources like seafood, the presence of plastic additives and residual monomers warrants attention. These findings highlight the need for stricter water quality standards, comprehensive investigation into exposure pathways and effective mitigation strategies.

BACKGROUND:3D printing has emerged as an attractive alternative for the fabrication of microfluidic devices offering the ability for rapid prototyping and a high degree of customization, in contrast to conventional microfabrication techniques. Despite its potential, the size of internal features (such as microfluidic channels) has been limited to larger cross-sectional areas and shorter lengths. Advances in 3D printing technology and the development of custom resins have allowed for smaller features to be obtained, moving the field closer to genuine microfluidic devices. However, not all researchers can readily perform the customization or resin development required. RESULTS:In this work, we obtained channels with smaller cross-sections (∼100-200 μm) and longer channel lengths (up to 96 mm) using a commercial printer and resin, by optimizing several printing parameters as well as aspects of the microfluidic design. A chip array and custom 3D printed manifold was used to develop a workflow for high throughput post-processing, enabling facile removal of uncured resin from enclosed channels. Using a rectangular channel geometry, a layer height of 50 μm, and a single layer cover, channels with specified dimensions of 150 × 150 μm and 6 mm total length were obtained with a high success rate (>98 %). Channels up to 96 mm could be printed using dimensions of 200 × 200 μm. The potential for these microchips for the pre-concentration and separation of proteins was also demonstrated, by fabricating polyacrylamide separation gels within the channels. SIGNIFICANCE:This work presents an alternative workflow for fabrication of enclosed channels that does not rely on the use of custom printers or resins. Implementation of this workflow with pre-existing 3D printing technology is expected to allow future research progress facilitating smaller channel dimensions of longer lengths more readily. If coupled with emerging 3D printing technology, this could open the door for the development of truly microfluidic devices for bioanalysis and point-of-care devices in healthcare settings.

BACKGROUND:Soil pollution by heavy metals from extensive exploration and processing has increased the demand for their analysis in soil. Traditional analysis is mostly laboratory-based due to the requirement for sample preparation, e.g., utilising HNO3 to digest and extract the heavy metals in solid soil matrix into a liquid matrix. This not only lengthens the analysis process but also reduces the feasibility of in-field analysis because of the use of hazardous chemicals. Alternative approaches that are low-cost and environmentally friendly, while also allowing in-field analysis with minimal skill requirements need to be developed for better screening and monitoring purposes. RESULTS:An electrokinetic extraction system was developed for the direct quantification of Cu(II) in silica sand and tailings samples using a colorimetric polymer inclusion membrane (PIM). Using an electric field, heavy metals are mobilised from the silica sand and move into the PIM where they complex with the colorimetric reagent, 1-(2-pyridylazo)-2-naphthol (PAN), causing a colour change proportional to the Cu(II) concentration. This was explored with Cu(II) spiked into silica sand, whereby a linear detection range of 0.30 μg-2.35 μg of Cu(II) (equivalent to 1.20-9.40 μg of Cu(II) per gram of sand) was achieved. SIGNIFICANCE:This is the first demonstration of electrokinetic extraction of ions from a solid material and shows potential for minimising sample pretreatment processes for in-field chemical analysis. The system is small in size and dry-to-touch and enables quantification using a low sample volume while remaining easily portable. Quantification through image analysis reduces the requirement for specialised skills.

A unique method for determining chlorophyll content in microalgae is devised employing a gold interdigitated electrode (G-IDE) with a 10-µm gap, augmented by a nano-molecularly imprinted polymer (nano-MIP) and a titanium dioxide/multiwalled carbon nanotube (TiO2/MWCNT) nanocomposite. The nano-MIP, produced using chlorophyll template voids, successfully trapped chlorophyll, while the TiO2/MWCNT nanocomposite, synthesized by the sol–gel technique, exhibited a consistent distribution and anatase crystalline structure. The rebinding of procured chlorophyll powder, which was used as a template for nano-MIP synthesis, was identified with a high determination coefficient (R2 = 0.9857). By combining the TiO2/MWCNT nanocomposite with nano-MIP, the G-IDE sensing method achieved a slightly better R2 value of 0.9892 for detecting chlorophyll in microalgae. The presented G-IDE sensor showed a significant threefold enhancement in chlorophyll detection compared with commercially available chlorophyll powder. It had a detection limit of 0.917 mL (v/v) and a linear range that spanned from 10-6 to 1 mL. The effectiveness of the sensor in detecting chlorophyll in microalgae was confirmed through validation of its repeatability and reusability.

There is a current gap in sample preparation techniques integrating the separation of microplastics according to their different material types and particle sizes. We describe herein the Bidimensional Dynamic Magnetic Levitation (2D-MagLev) technique, enabling the resolution of mixtures of microplastics sorting them by plastic type and particle size. Separations are carried out in a bespoke flow cell sandwiched between two ring magnets and connected to programmable pumps for flow control. The first separation dimension is based on sequential increases in the concentration of a paramagnetic salt (MnCl2), enabling magnetic levitation of microplastics with determined densities. The second dimension is based on increasing flow rate gradients and maintaining constant MnCl2 concentrations. This fractionates the magnetically levitating microplastics according to their different particle sizes. Microplastics are therefore collected by their increasing density, and the particles corresponding to each density are fractionated from smaller to larger size. Using polyethylene microspheres with defined density (1.03-1.13 g cm-3) and size (98-390 μm) as microplastic mimicking materials, we investigated their optimum threshold velocities for their size fractionation, potential effects of medium viscosity and sample loading, and types of flow rate gradients (linear, step). Performing a separation using a combination of step gradients in both MnCl2 concentration and flow rate, mixtures comprising microplastics of two different densities and three different particle sizes were separated. 2D-MagLev is simple, fast, versatile, and robust, opening new avenues to facilitate the study of the environmental presence and impact of microplastics.

Despite the available 3D printing technologies, fabrication of miniaturized analytical systems with integrated functional components is still one of the largest impediments. Here, we integrate a permeable porous filter into a 3D printed fluidic device capable of withstanding moderate hand pressure for in-field colorimetric pH measurements. The pH indicator is loaded and dried into the device, and the pH determined from converting images taken by a smartphone camera to a chromaticity diagram in International Commission on Illumination (CIE) 1931 color space and compared to calibration standards. The portable miniaturized device was fabricated with an integrated porous structure using a PolyJet 3D printer. One hundred and thirty-six devices could be printed in a single run (136 min), with cost of $0.6 per device. The 3D printed devices are capable of filtering particulate matter from the sample before mixing with an indicator avoiding optical interferences. Different environmental samples with a wide pH range (3-10) can be measured rapidly within 1 min.

Multiple-step on-line preconcentration, a combination of at least two stacking techniques has been developed to increase the sensitivity in capillary electrophoresis (CE) for analytes in various samples. It is usually conducted sequentially, or in some cases, synergistically, where different stacking modes occur simultaneously. Multiple-step techniques allow simultaneous preconcentration and separation of various kinds of analytes in different complex samples in a single CE run. This review aims to provide recent advances in multiple-step on-line preconcentration techniques in CE. We critically review technical papers published for the last 7 years up until July 2024, subsequently organized according to the combination of the main stacking techniques, that is, field amplification, large volume sample stacking, transient isotachophoresis, micelle to solvent or micelle to cyclodextrin stacking, and others. The procedures, fundamental mechanism, analytical figures of merits achieved, and their feasibility for complicated sample matrices are reviewed.

Per‐ and polyfluoroalkyl substances (PFAS) are a class of hazardous pollutant that are ubiquitous in our modern world. Current research is driven by an increased awareness and concern regarding the safety of PFAS for the general population, while tightening regulations have prompted the need for detection and quantification techniques from a wide range of matrices. PFAS are a group of molecules offering unique behaviours, hazards, and complications that are not obvious or readily apparent from reading the literature. These peculiarities can impede or convolute analyses when not considered in experimental design. Drawing on the knowledge of a range of literature sources, this tutorial review looks to highlight and amalgamate the valuable suggestions and methodologies currently available to enable successful PFAS research in any laboratory.

The water issue has emerged as a significant concern in the current century, mostly attributed to the exponential rise of the worldwide population and the process of globalization. Nanoscience and nanotechnology have emerged as crucial tools in effectively tackling a diverse array of water pollution challenges through the implementation of innovative and efficacious remedies. There has been a significant amount of attention given to the identification and management of new chemical pollutants in recent times. Consequently, it is desired to have dependable and expeditious analytical instruments that possess the capability to conduct sample analysis with heightened sensitivity, extensive selectivity, desirable durability, and less sample manipulation for the identification, breakdown, and elimination of perilous pollutants. This review examines the several gold–carbon nanocomposites-based systems that have been established to date. This paper examines the chemical functionalization of gold-carbon nanocomposites, focusing on its role in providing stable platforms, enabling different applications, and facilitating effective monitoring of water contaminants. The present study discusses the challenges faced in previous research and the potential future utilization of gold-carbon nanocomposites in prognostic sampling for real-time assessment of water quality. This approach offers a promising avenue for addressing the global water issue.

Safety and the quality of products rely on proper cleanliness procedures and good manufacturing practices in the production environment. The use of swabs for the collection of samples from surfaces has been a common practice in industries, medicine and forensic studies. To accommodate these different purposes, many varieties of swabs have been introduced into the market, and it is important to assess the performance of these swabs before incorporating into an environmental monitoring procedure. The overall effectiveness of a swab is determined by two factors: the number of bacteria that a swab can uptake from a surface and the number of picked-up bacteria the swab can elute into a releasing buffer. This study evaluated the uptake efficiency and release efficiency of four different commercially available swabs: CleanFoam (Texwipes, USA), FLOQSwabs (Copan diagnostic Inc., USA), Hydraflock swabs (Puritan medical products, USA), and Cotton swabs. Cotton swabs showed the highest uptake efficiency (96.5 ± 1.9%), whereas CleanFoam swabs (57.9 ± 20.3%) showed the least. Both flocked (FLOQSwabs and Hydraflock) swabs showed over 80% uptake efficiency. Releasing efficiency of swabs was tested with eight different releasing buffers. Cotton swabs displayed the lowest release efficiency with most of the tested releasing buffers. When employed with Tris HEPES, Tris MOPS, Tris TAPS, FLOQSwabs, and Hydraflock swabs exhibited releasing efficiency of over 75%. The overall efficiency of the swabs was determined using TAPS as the releasing buffer and the values obtained were 80.4 ± 9.8%, 54.7 ± 16.9%, 35.0 ± 12.7% and 25.2 ± 6.9% for Hydraflock swabs, FLOQSwabs, Cotton swabs and Cleanfoam swabs, respectively.

BACKGROUND:The quantification of microbes, particularly live bacteria, is of utmost importance in assessing the quality of meat products. In the context of meat processing facilities, prompt identification and removal of contaminated carcasses or surfaces is crucial to ensuring the continuous production of safe meat for human consumption. The plate count method and other traditional detection methods are not only labour-intensive but also time-consuming taking 24-48 h. RESULTS:In this report, we present a novel isotachophoretic quantification method utilizing two nucleic acid stains, SYTO9 and propionic iodide, for the detection of total viable bacteria. The study employed E. coli M23 bacteria as a model organism, with an analysis time of only 30 min. The method demonstrated a limit of detection (LOD) of 184 CFU mL-1 and 14 cells mL-1 for total viable count and total cell count, respectively. Furthermore, this new approach is capable of detecting the microbial quality standard limits for food contacting surfaces (10 CFU cm-2) and meat (1.99 × 104 CFU cm-2) by swabbing an area of 10 × 10 cm2. SIGNIFICANCE:In contrast to the culture-based methods usually employed in food processing facilities, this isotachophoretic technique enables easy and rapid detection (<30 min) of microorganisms, facilitating crucial decision-making essential for maintaining product quality and safety.

Methamphetamine (MA) is one of the most virulent illicit drugs that can be synthesized from household materials leading to its prevalent trafficking and local manufacturing in clandestine drug laboratories (clan labs). The significant problems of tracing MA in clan labs and monitoring drug abusers lie in the lag time between sample collection and analysis and the number of tests done. Capillary electrophoresis (CE) is a rapid separation technique amenable to miniaturization and field testing. Herein, we developed a simple transient isotachophoretic (tITP)-CE method to detect MA and its precursor pseudoephedrine (PSE) in clan labs and non-invasive biological fluids. The method was implemented on the ETD-100, a commercial fully automated portable CE instrument with an integrated swab-based extraction system. Within 2 min of insertion of the swab, MA and PSE were automatically extracted with a leading electrolyte (LE) and then separated on covalently modified capillaries. The ETD-100 showed a limit of detection (LOD) and quantification (LOQ) of MA 0.02 and 0.05 mu g/swab and 0.02 and 0.06 mu g/swab of PSE, with an enhancement factor of 118 and 328, respectively, when compared to a normal nontITP injection. The intra and inter-day relative standard deviation in terms of migration time were in the range of 0.75-1.93 % for both MA and PSE and were 2.0-2.4 % for both MA and PSE peak height. The method was demonstrated with the detection of spiked MA and PSE on different household materials as well as in noninvasive biological fluids with a recovery above 60 %.

Sample preparation techniques enabling the separation and cleanup of nanoplastics removing other components present in complex sample matrices are scarce. Herein, micro-electromembrane extraction (μ-EME) has been explored for this purpose based on the extraction of nanoplastic particles across a free liquid membrane (FLM). The extraction unit is based on a perfluoroalkoxy tube sequentially filled with the acceptor solution (20 μL 5 mM phosphate buffer, pH 10.7), FLM (10 μL 1-pentanol), and donor solution (20 μL sample/standard solution). Sulfonated polystyrene beads (200 nm particle size) were selected as a model mimicking negatively charged nanoplastics. At 700 V, nanoplastics transferred from the donor solution into the FLM before moving across the FLM into the acceptor solution. Quantitative nanoplastic measurements after μ-EME were performed by injecting the acceptor solution into a capillary electrophoresis system with diode array detection. μ-EME allowed the rapid nanoplastic sample cleanup, requiring an extraction time of just 90 s and obtaining a nanoplastic transfer yield through the FLM of 60% with RSD values below 9%. The μ-EME technique enabled the efficient sample matrix cleanup of nanoplastics spiked in different tea matrices. Nanoplastic transfer yield through the FLM for black tea and flavored tea matrices were 56% and 47%, respectively, with complete sample matrix removal of UV-absorbing compounds.

Asymmetric micro-electromembrane extraction (µ-EME) based on a free liquid membrane has been evaluated for the preconcentration of nanoplastics. A conical unit (200 µL micropipette tip) enabled the simple and reproducible formation of the required three-phase extraction system consisting of a donor solution (150 µL sample/standard solution), free liquid membrane (FLM; 10 µL 1-pentanol), and an acceptor solution (5 µL of 5 mM phosphate buffer, pH 10.7). After µ-EME, nanoplastics transferred across the FLM into the acceptor solution were quantified using capillary zone electrophoresis with diode array detection. Enrichment factors >20 and extraction recoveries >70 % were achieved for nanoplastics concentrated at 500 V during 5 min. The limit of detection (LOD, S/N = 3) and limit of quantification (LOQ, S/N = 10) of the method using 200 nm sulphonated polystyrene particles as model nanoplastics were 6.00×10−4% (w/v) and 2.00×10−3% (w/v), respectively. Intraday (n = 6) and interday (n = 6) repeatability%RSD for 5.5 × 10−3% (w/v) nanoplastics were 8.5 % and 7.2 %, respectively. µ-EME enabled an efficient sample matrix clean-up and preconcentration of nanoplastics spiked in tea sample matrices. Nanoplastics preconcentrated through the FLM for black tea resulted in an enrichment factor of 20±3.6 (n = 3), with complete sample matrix removal of UV absorbing compounds.

This study examines the effects of pulsed light-emitting diode (LED) irradiation across five representative photoredox reactions employing six established photocatalysts. The primary objective of this investigation was to develop a better understanding of the potential effects and broader scope of pulsed irradiation in photoredox catalysis, which the results suggest may influence reaction progress positively, negatively, or negligibly. These effects appear to vary depending on the specific reaction, the identity of the photoredox catalyst and can even differ between substrates. Accordingly, unraveling the fundamental mechanistic basis of these effects is both challenging and nuanced; however, our results do highlight the importance of properly considering the Bunsen-Roscoe Law during photoredox reaction design.

Functionalized porphyrin molecules were found to change color in the presence of perfluorocarboxylic acids (PFCAs). The porphyrin molecules allow for simple visual- and color space-based detection of PFCAs across a range of concentrations.