Amperometric Detection Research Articles

Electrochemical sensing of cysteine using a novel carbon black and cobalt phthalocyanine composite

In this work, a novel composite material using carbon black and cobalt phthalocyanine (CoPc/CB) was produced. Characterizations by spectroscopic techniques (Raman and infrared), scanning electron microscopy, and X-ray diffraction confirmed the formation of the composite material. The proposed material was cast on the glassy carbon electrode surface, and its electrochemical sensing properties were checked using cysteine (CYS), an important amino acid widely used in medicine, food additives, and cosmetics, as a model molecule. Studies by cyclic voltammetry revealed that the modified electrode caused considerable electrocatalytic effects (detection at a potential close to 0.1 V) and enhanced in peak current compared to the unmodified electrode. A wide linear range (1—150 µmol/L) and adequate detectability (LOD = 0.75 µmol/L) were achieved by Batch Injection Analysis (BIA) with amperometric detection. Repeatability tests (n = 20) at two concentration levels (20 and 40 µmol/L) confirmed the precision of the method (RSD < 11 %). Interestingly, even under high flow conditions, good stability of the electrode modification was noticed. The proposed method was applied to determine CYS concentration in pharmaceutical samples, where adequate recovery values (89 and 110 %) and results statistically similar to those achieved by capillary electrophoresis indicated the accuracy and reliability of the electrochemical analyses.

Ultrasensitive Electroanalytical Detection of Pb2+ and H2O2 Using Bi and Fe-Based Nanoparticles Embedded into Porous Carbon Xerogel-The Influence of Nanocomposite Pyrolysis Temperatures.

Multifunctional materials based on carbon xerogel (CX) with embedded bismuth (Bi) and iron (Fe) nanoparticles are tested for ultrasensitive amperometric detection of lead cation (Pb2+) and hydrogen peroxide (H2O2). The prepared CXBiFe-T nanocomposites were annealed at different pyrolysis temperatures (T, between 600 and 1050 °C) and characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption, dynamic light scattering (DLS), and electron microscopies (SEM/EDX and TEM). Electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWV) performed at glassy carbon (GC) electrodes modified with chitosan (Chi)-CXBiFe-T evidenced that GC/Chi-CXBiFe-1050 electrodes exhibit excellent analytical behavior for Pb2+ and H2O2 amperometric detection: high sensitivity for Pb2+ (9.2·105 µA/µM) and outstanding limits of detection (97 fM, signal-to-noise ratio 3) for Pb2+, and remarkable for H2O2 (2.51 µM). The notable improvements were found to be favored by the increase in pyrolysis temperature. Multi-scale parameters such as (i) graphitization, densification of carbon support, and oxide nanoparticle reduction and purification were considered key aspects in the correlation between material properties and electrochemical response, followed by other effects such as (ii) average nanoparticle and Voronoi domain dimensions and (iii) average CXBiFe-T aggregate dimension.

An oxygen-insensitive amperometric galactose biosensor based on galactose oxidase co-immobilized with an Os-complex modified redox polymer

Monitoring galactose levels in dairy products can help to prevent severe complications with a hereditary metabolic disease such as galactosemia, a life-threatening disease. The current state of the art requires the development of less expensive, more reliable and specific methods to determine galactose levels in food in a practical way. We report the development and optimization of an amperometric biosensor for determination of galactose in dairy products based on galactose oxidase (GaOx) co-immobilized with an osmium-complex modified redox polymer on glassy carbon electrodes. To attain the maximum catalytic currents based on mediated electron transfer, two Os-complex based polymers with different redox potentials and different enzyme:redox polymer ratios were studied. The optimized GaOx-modified electrode gave a maximum electrocatalytic response of galactose oxidation that was not affected by the presence of O2, indicating fast wiring of the enzyme by the Os-complex modified redox polymer. The biosensor that gave the best analytical parameters for galactose detection was further tested for measuring galactose concentration in lactose-containing and lactose-free milk and yogurt samples under aerobic conditions. The results obtained with the amperometric biosensor were validated by high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD).

Ultrasensitive Detection of Hydrogen Peroxide Using Methylene Blue Grafted on Molecular Wires as Nanozyme with Catalase-like Activity.

In this study, we present the development of an electrochemical sensor designed for ultrasensitive detection of endogenous H2O2. This sensor relies on signal amplification achieved through nanozyme activity exhibited by methylene blue (MB) grafted onto a peptide support. The sensor exhibited excellent selectivity and sensitivity, with a limit of detection of 18 nM and a linear detection range of 20-200 nM. Thus, we have validated the concept of the MB-peptide system, serving as both an electroactive label and a catalyst for H2O2 decomposition under electrochemical conditions. The implemented signal amplification system enables the rapid detection of H2O2, with an overall assay time of 1-2 min, a significant improvement compared to amperometric detection using surface-immobilized enzymes.

Fructan Catabolism by Rumen Microbiota of Cattle and Sheep

Fructans serve as the primary form of storage carbohydrate in cool-season grasses, but little is known about potential differences in ruminal fermentation of fructans between cattle and sheep. An ex vivo study was conducted to evaluate species differences in fructan catabolism. Buffered media containing ground orchardgrass (Dactylis glomerata L.) substrate was inoculated with uncultivated rumen microbiota obtained from cattle and sheep (n = 4 species−1). Fructan profiles were monitored over the incubation period (8 h; 39 °C) using high-performance anion-exchange chromatography coupled to pulsed amperometric detection (HPAEC-PAD). In both species, disappearance of long-chain fructans (degree of polymerization [DP] &gt; 8) was evident by 2 h of incubation (p &lt; 0.01), whereas short-chain fructans (DP 4–8) increased from 0 to 2 h prior to subsequent degradation (p &lt; 0.01). However, the overall rate of long-chain fructan catabolism was greater in bovine versus ovine fermentations, particularly between 2 and 4 h (p &lt; 0.01). Additionally, rapid utilization of short-chain fructans occurred from 2 to 4 h in bovine fermentations, but was delayed in ovine fermentations, with substantial degradation occurring only after 4 h of incubation (p &lt; 0.01). These results indicate that rumen microbiota of cattle may have a greater capacity for fructan degradation.

A graphitized carbon@boron carbide-mediated laccase-based amperometric biosensor for epinephrine detection

The development of novel electron transfer mediator is important for laccase-based electrochemical biosensors. Here, graphitized carbon coated boron carbide (GC@B4C) was first used as the mediator to transfer electrons from laccase (Lac) to nickel foam (NF) electrode. The GC shell of GC@B4C particles was characterized and confirmed by HRTEM, XRD and Raman spectroscopy. The fabricated Lac/GC@B4C/NF electrode was applied for amperometric detection of epinephrine (EP). Detection results indicated Lac/GC@B4C/NF electrode has wide linear range (0.1 µM-2.6 mM), low detection limit (40 nM), high sensitivity (76.05 µA mM−1), strong anti-interference ability and favorable stability for EP detection. This work opened up the use of nonmetallic carbide as the mediator for enzyme-based electrochemical biosensors.

Acid hydrolysis conditions for quantification of meningococcal X polysaccharide in a pentavalent vaccine using HPAEC-PAD/ESI-MS

A selective and sensitive method was evaluated for quantitation of meningococcal X (Men X) polysaccharide in pentavalent meningococcal A, C, W, Y and X conjugate vaccine using different acid hydrolysis conditions like HCl, TFA, HF, HF-TFA, and HF–HCl. High-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) using CarboPac PA10 column was used to identify the hydrolyzed products based on retention time and its comparison with monosaccharide standards. Complete release of glucosamine (GlcN) from Men X in monovalent bulk and pentavalent vaccine samples was achieved using HF hydrolysis at 80 °C for 2 h. The Men X HF-hydrolyzed polysaccharide to glucosamine along with the reference standard was identified using collision-induced dissociation (CID) electrospray mass spectroscopy and the MS/MS fragments of m/z 162, m/z 144 and m/z 84. Meningococcal polysaccharide concentration was determined with a correlation coefficient r2 >0.99 using polysaccharide reference standard. The serogroups A, W, and Y were converted to their monosaccharides units and quantified using this method however, milder acid hydrolysis 0.1 M HCl 80 °C 2 h for release of sialic acid for Men C polysaccharide was found to be more suitable. These methods will provide necessary tools and prove to be beneficial to laboratories developing new saccharide-based vaccine combinations.

Ruthenium-Anchored Carbon Sphere-Customized Sensor for the Selective Amperometric Detection of Melatonin.

Melatonin (MT), a pineal gland hormone, regulates the sleep/wake cycle and is a potential biomarker for neurodegenerative disorders, depression, hypertension, and several cancers, including prostate cancer and hepatocarcinoma. The amperometric detection of MT was achieved using a sensor customized with ruthenium-incorporated carbon spheres (Ru-CS), possessing C- and O-rich catalytically active Ru surfaces. The non-covalent interactions and ion-molecule adducts between Ru and CS favor the formation of heterojunctions at the sensor-analyte interface, thus accelerating the reactions towards MT. The Ru-CS/Screen-printed carbon electrode (SPCE) sensor demonstrated the outstanding electrocatalytic oxidation of MT owing to its high surface area and heterogeneous rate constants and afforded a lower detection limit (0.27 μM), high sensitivity (0.85 μA μM -1 cm-2), and excellent selectivity for MT with the co-existence of crucial neurotransmitters, including norepinephrine, epinephrine, dopamine, and serotonin. High concentrations of active biomolecules, such as ascorbic acid and tyrosine, did not interfere with MT detection. The practical feasibility of the sensor for MT detection in pharmaceutical samples was demonstrated, comparable to the data provided on the product labels. The developed amperometric sensor is highly suitable for the quality control of medicines because of its low cost, simplicity, small sample size, speed of analysis, and potential for automation.

Determination of inorganic ions and carbohydrates in cardioplegia and nephroplegia solutions by ion chromatography.

In this study, methods for analyzing inorganic ions and carbohydrates in cardioplegia and nephroplegia solutions were developed and validated using ion chromatography with both conductivity and pulsed amperometric detection. The inorganic ions such as sodium, potassium, and calcium were separated by a cation-exchange column with 27mM methanesulfonic acid as mobile phase at 0.5mL/min. The anion (chloride) and carbohydrates (mannitol and glucose) were analyzed by an anion-exchange column using a mobile phase of 20mM sodium hydroxide at 1.0mL/min. The methods showed a high sensitivity for all analytes, with quantification limits from 0.0002 to 0.06mg/L. Good linearities between the peak areas and concentrations were found for all analytes within the selected concentration range (R2 >0.999). Relative standard deviation values for repeatability and interday precision were 0.1%-1.0% and 0.7%-1.6%, respectively. The accuracy was validated by determining the percentage recovery, which was between 98.0% and 101.3% for all analytes, indicating good accuracy of the methods. The robustness was verified by using an experimental design. Finally, real samples were analyzed to determine the content of the analytes. All assay values were between 96.8% and 102.5%.

Cobalt-based metal-organic framework-functionalized graphene oxide modified electrode as a new electrochemical sensing platform for detection of free chlorine in aqueous solution

This work reports the profit of using a MOF compound for developing a sensitive electrochemical sensor to free chlorine detection in an aqueous solution. Co-MOF and FGO composites were synthesized and combined with the carbon paste (CP) to prepare an efficient electrochemical sensor with high sensing ability. The fabricated Co-MOF and FGO composites were characterized by SEM, EDX, FT-IR, and XRD techniques. Meanwhile, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were utilized to assess the electrochemical performance of the Co-MOF-FGO/CP modified electrode. Under the optimized condition, the amperometric detection showed that the reduction current of free chlorine increased linearly with a coefficient determination of 0.995 during its wide concentration range of 0.1–700 ppm. Also the detection limit (LOD) (S/N = 3) was 0.01 ppm. The selectivity of the sensor was tested with possible interferences, and satisfactory results were obtained. The proposed sensor was successfully used to determine the free chlorine in tap water and swimming pool water real samples. The results suggested that this proposed sensor could pave the way for developing the electrochemical sensor of free chlorine in aqueous media with MOFs.

Deep eutectic solvents combined with beta-cyclodextrin derivatives for chiral separation of typical adrenergic receptor agonists by capillary electrophoresis with amperometric detection

Enantioseparation has always been one of the research hotspots and difficulties in the field of modern separation science. In this work, a binary chiral electrophoretic separation system was constructed using deep eutectic solvents (DESs) coupled with beta-cyclodextrin derivatives based on capillary electrophoresis with amperometric detection system, and five groups of typical adrenergic receptor agonists (adrenaline, salbutamol, isoproterenol, norepinephrine and terbutaline) were selected as the model enantiomers. The effects of additive types and contents of DESs and cyclodextrins, and the pH value and concentration of the running buffer on the resolution of the selected chiral compounds were investigated in detail. The mechanism of DESs improving separation was explored preliminarily by means of UV spectrophotometry, which was further verified based on the comparison of single and mixed components of choline chlorine-urea DES. Under the optimum conditions, the relative standard deviations for inter-day and intra-day repeatability of the migration time, peak area and resolution for adrenaline and salbutamol were within 8.7%, and the limits of detection reached 0.030 μg mL−1 (S/N = 3). The recovery data were in the range of 96.3–118.7%. The developed methods have been applied for the analyses of (+)-adrenaline hydrochloride injection and (±)-salbutamol aerosol. This binary chiral electrophoretic separation system by CE-AD has high detection sensitivity and low analytical cost, providing an alternative for the separation and analysis of chiral drugs.

Diabetes Management by Fourth-Generation Glucose Sensors Based on Lemon-Extract-Supported CuO Nanoporous Materials.

Diabetes is a major worldwide health issue, impacting millions of people around the globe and putting pressure on healthcare systems. Accurate detection of glucose is critical for efficient diabetes care, because it allows for prompt action to control blood sugar levels and avoid problems. Reliable glucose-sensing devices provide individuals with real-time information, allowing them to make more educated food, medicine, and lifestyle decisions. The progress of glucose sensing holds the key to increasing the quality of life for diabetics and lowering the burden of this prevalent condition. The present investigation addresses the synthesis of a CuO@lemon-extract nanoporous material using the sol-gel process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the morphological properties of the composite, which revealed a homogeneous integration of CuO nanoparticles (NPs) on the surface of the matrix. The existence of primarily oxidized copper species, especially CuO, was confirmed by X-ray diffraction spectroscopy (XRD) investigation in combination with energy-dispersive X-ray (EDX) spectroscopy. The CuO@lemon-extract-modified glassy carbon electrode (CuO@lemon-extract GCE) performed well in non-enzymatic electrochemical sensing applications such as differential pulse voltammetry (DPV) and amperometric glucose detection. The electrode achieved a notable sensitivity of 3293 µA mM-1 cm-2 after careful adjustment, with a noticeable detection limit of 0.01 µM (signal-to-noise ratio of 3). The operational range of the electrode was 0.01 µM to 0.2 µM, with potential applied of 0.53 V vs. Ag/AgCl. These findings underscore the CuO@lemon-extract GCE's promise as a robust and reliable platform for electrochemical glucose sensing, promising advances in non-enzymatic glucose sensing (NEGS) techniques.

Plasma measurements of the dual sugar test reveal carbohydrate immediately alleviates intestinal permeability caused by exertional heat stress.

The aim of this set of randomised cross-over studies was to determine the impact of progressive heat exposure and carbohydrate or protein feeding during exertional stress on small intestine permeability using a dual sugar test. In our previous work, and typically in the field, recovery of lactulose and l-rhamnose is measured cumulatively in urine. This follow-up study exploits our novel high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) protocol to accurately quantify the sugars in plasma. Endurance-trained participants completed experimental trial A (ET-A; n=8), consisting of 2h running at 60% in temperate, warm and hot ambient conditions, and/or experimental trial B (ET-B; n=9), consisting of 2h running at 60% in the heat while consuming water, carbohydrate or protein. Blood samples were collected and plasma lactulose (L) and l-rhamnose (R) appearance, after dual sugar solution ingestion at 90min of exercise, was quantified by HPAEC-PAD to measure plasma L/R and reveal new information about intestinal permeability immediately post-exercise and during recovery. In ET-A, plasma L/R increased immediately post-exercise in hot compared with temperate and warm conditions, while, in ET-B, carbohydrate alleviated this, and this information was otherwise missed when measuring urine L/R. Consuming carbohydrate or protein before and during exercise attenuated small intestine permeability throughout recovery from exertional heat stress. We recommend using the dual sugar test with quantification of plasma sugars by HPAEC-PAD at intervals to maximise intestinal permeability data collection in exercise gastroenterology research, as this gives additional information compared to urinary measurements. KEY POINTS: Intestinal permeability is typically assessed using a dual sugar test, by administering a drink containing non-metabolisable sugars (e.g. lactulose (L) and l-rhamnose (R)) that can enter the circulation by paracellular translocation when the epithelium is compromised, and are subsequently measured in urine. We demonstrate that our recently developed ion chromatography protocol can be used to accurately quantify the L/R ratio in plasma, and that measuring L/R in plasma collected at intervals during the post-exercise recovery period reveals novel acute response information compared to measuring 5-h cumulative urine L/R. We confirm that exercising in hot ambient conditions increases intestinal epithelial permeability immediately after exercise, while consuming carbohydrate or protein immediately before and during exercise attenuates this. We recommend using our dual sugar absorption test protocol to maximise intestinal epithelial permeability data collection in exercise gastroenterology research and beyond.

Amperometric flow injection analysis of hydroquinone in dermatological creams using a porous diamond-like carbon electrode

A porous diamond-like carbon film deposited on vertically aligned multi-walled carbon nanotubes (DLC:VAMWCNT) was evaluated as an electrode material in flow injection analysis (FIA) with amperometric detection. The redox behavior of hydroquinone (H2Q) was carried out as proof of concept. From cyclic voltammetry tests, H2Q gave a heterogeneous electron transfer rate constant (k0) of 4.9 × 10−3 cm s−1, which is comparable or better than those obtained with conventional electrodes. For the H2Q determination with the FIA-amperometry system, optimizations were performed regarding the supporting electrolyte, applied potential and FIA parameters (flow rate and sample injection volume). Under optimal conditions, the amperometric response of the DLC:VAMWCNT electrode was linear in the H2Q concentration range from 1.0 × 10−6 to 1.0 × 10−4 mol L−1, with a limit of detection (LOD) of 7.7 × 10−7 mol L−1. Interestingly, the DLC:VAMWCNT electrode displayed a very stable response under hydrodynamic conditions, with no memory effect while retaining accuracy towards the analysis of commercial H2Q-based dermatological creams. From these findings, DLC:VAMWCNT appears to be an outstanding candidate for flow injection analysis systems coupled to electrochemical detection.

Green reduction and uniform assembly of silver nanoparticles on polydopamine functionalized sulfur-doped graphitic carbon nitride nanosheets for highly sensitive H2O2 detection via nonenzymatic approach

In this study, we demonstrate a new strategy to fabricate an enzyme-free hydrogen peroxide (H2O2) sensor electrode based on silver nanoparticles (AgNPs) decorated polydopamine/sulfur-doped graphitic carbon nanocomposite (denoted as AgNPs@PDA/S-g-C3N4). The S-g-C3N4 nanosheets are derived from the pyrolysis of trithiocyanouric acid, followed by thermal exfoliation. A mussel-inspired PDA nanolayer enhances the solubility and high dispersion of S-g-C3N4 nanosheets and AgNPs in aqueous phase synthesis. The amine and catecholic functional groups of PDA are the major nucleation sites for Ag+ ions adsorption and ascorbic acid was further used as a green reducing agent for the growth of AgNPs. PDA adhesion layer can effectively connect the AgNPs and S-g-C3N4 nanosheets via electrostatic interaction to increase the stability and biocompatibility of the ternary composite structure. Various spectroscopy and microscopy techniques confirmed the formation of AgNPs@PDA/S-g-C3N4 nanocomposite. Our AgNPs@PDA/S-g-C3N4 nanocomposite fabricated disposable sensor exhibited outstanding sensing ability to H2O2 reduction at −0.65 V (vs. Ag/AgCl), which is confirmed through an amperometric detection method. The sensor exhibits rapid response (2 s) to H2O2 sensing with high sensitivity (1020 μA mM−1 cm−2), wide detection range (0.002–23 mM) and low limit of detection of 0.086 μM. The practicality of the H2O2 sensor was evaluated with commercial milk and mouthwash samples, which retained satisfactory recoveries. Thus, our results indicate that the PDA functionalization not only enhances the S-g-C3N4 solubility but also increases the interfacial charge transport in AgNPs@PDA/S-g-C3N4 nanocomposite material which develops a potential sensing method for nonenzymatic H2O2 sensor. Due to the effective surface modification strategies, such as PDA nanocoating and AgNPs deposition, the exfoliated S-g-C3N4 nanosheets gained excellent electrochemical properties, facilitating potential candidates in electrochemical applications.

Lactational and geographical variation in the concentration of six oligosaccharides in Chinese breast milk: a multicenter study over 13 months postpartum.

Understanding the variations of oligosaccharide in breast milk contribute to better study how human milk oligosaccharides (HMOs) play a role in health-promoting benefits in infants. Six abundant HMOs, 2'-fucosyllactose (2'-FL), 3-fucosyllactose (3-FL), Lacto-N-tetraose (LNT), Lacto-N-neotetraose (LNnT), 3'-sialyllactose (3'-SL) and 6'-sialyllactose (6'-SL), in breast milk collected at 0-5 days, 10-15 days, 40-45 days, 200-240 days, and 300-400 days postpartum from six locations across China were analyzed using high-performance anion-exchange chromatography-pulsed amperometric detector. The concentration of individual HMO fluctuated dynamically during lactational stages. The median ranges of 2'-FL, 3-FL, LNT, LNnT, 3'-SL, and 6'-SL across the five lactational stages were 935-2865 mg/L, 206-1325 mg/L, 300-1473 mg/L, 32-317 mg/L, 106-228 mg/L, and 20-616 mg/L, respectively. The prominent variation was observed in the content of 6'-SL, which demonstrates a pattern of initial increase followed by a subsequent decrease. Among the five lactational stages, the transitional milk has the highest concentration, which was 31 times greater than the concentration in mature milk at 300-400 days postpartum, where the content is the lowest. Geographical location also influenced the content of HMOs. LNT and LNnT were the highest in mature milk of mothers from Lanzhou among the six sites at 40-240 days postpartum. Breast milks were categorized into two groups base on the abundance of 2'-FL (high and low). There was no significant difference in the proportions of high and low 2'-FL phenotypes among the six sites, and the percentages of high and low 2'-FL phenotypes were 79% and 21%, respectively, across all sites in China. This study provided a comprehensive dataset on 6 HMOs concentrations in Chinese breast milk during the extended postpartum period across a wide geographic range and stratified by high and low 2'-FL phenotypes.

Disposable electrochemical immunoplatform to shed light on the role of the multifunctional glycoprotein TIM-1 in cancer cells invasion

Detecting overexpression of cancer biomarkers is an excellent tool for diagnostic/prognostic and follow-up of patients with cancer or their response to treatment. This work illustrates the relevance of interrogating the levels of T-cell immunoglobulin and mucin domain 1 (TIM-1) protein as a diagnostic/prognostic biomarker of high-prevalence breast and lung cancers by using an amperometric disposable magnetic microparticles-assisted immunoplatform. The developed method integrates the inherent advantages of carboxylic acid-functionalized magnetic beads (HOOC-MBs) as pre-concentrator support and the amperometric transduction at screen-printed carbon electrodes (SPCEs). The immunoplatform involves a sandwich-type immunoassay assembled on HOOC-MBs through the specific capture/labeling of TIM-1 using capture antibodies and horseradish peroxidase (HRP)-conjugated biotinylated detection antibodies as biorecognition elements. The magnetic immunoconjugates were confined onto the working electrode (WE) surface of the SPCEs for amperometric detection using the hydroquinone/hydrogen peroxide/HRP (HQ/H2O2/HRP) redox system. The method allows the selective detection of TIM-1 protein over the 87–7500 pg mL−1 concentration range in only 45 min, with a limit of detection of 26 pg mL−1. The developed bioplatform was successfully applied to the analysis of breast and lung cancer cell extracts, providing the first quantitative results of the target glycoprotein in these types of samples.

Elements and sugars in kelp and fucoid species in Greenland, correlation and seasonality

Greenland seaweeds constitute an arctic marine resource as well as being important monitoring organisms in connection with arctic mining activities. In both cases, the natural element content, and its potential seasonal variation, is important knowledge for designing a monitoring programme and for planning of harvest for highest biomass quality and value. Therefore, concentration levels of 54 elements and two sugars (laminarin and mannitol) were obtained in seven different seaweed species of relevance for monitoring and commercial harvest sampled in the same location in Greenland across all seasons during two years. The kelp species sampled were Agarum clathratum, Alaria esculenta, Hedohyllum nigripes, Saccharina latissima, and the fucoids Ascophyllum nodosum, Fucus distichus and F. vesiculosus. The thallus samples were analysed for element concentration levels by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and the monosaccharides were separated by HPAEC ion exchange and detected using Pulsed Amperometric Detection (gold electrode). The results showed, in the studied location, and on average, that the dominant major and minor elements are potassium, sodium, calcium, magnesium and phosphorus with mean concentration levels > 4800 μg g−1. The trace elements are dominated by iron, aluminium and arsenic with mean concentration levels > 61 μg g−1. Concentration levels of elements were in general seaweed species specific. Seasonality was not tested statistically significant for most of the elements when data were pooled in summer and winter months, although higher concentration levels during winter could be observed. Thus, the content of laminarin and mannitol is highest during late summer, thus July–October/November may be the time window for optimal harvest yield with respect to those compounds, although narrower time windows may be considered, depending on the species harvested. Regarding unwanted compounds such as As and I, harvesting time of the year seems not to cause a profound difference on the quality of the biomass.

Fabrication of carbon nanospheres functionalized Sm2O3/Co3O4 novel hybrid nanocomposites for selective and sensitive amperometric detection of hydrogen peroxide

Fabrication of carbon nanospheres functionalized Sm2O3/Co3O4 novel hybrid nanocomposites for selective and sensitive amperometric detection of hydrogen peroxide

(Invited) integration of Microneedles and Electrochemical Sensors for Medical Applications

Microneedles are small-scale devices that may be used for access to interstitial fluid and/or capillary blood for transdermal monitoring of chemicals [1]. In this presentation, the integration of several types of electrochemical sensors with hollow microneedles will be considered. For example, carbon fiber electrodes have been integrated with digital micromirror device-produced microneedles; ascorbic acid and hydrogen peroxide were detected with these devices [2]. Carbon paste electrodes have also been integrated with digital micromirror device-produced microneedles; electrodes made from rhodium-dispersed carbon paste were used for hydrogen peroxide sensing [3]. In addition, lactate oxidase-modified rhodium-dispersed carbon paste electrodes were demonstrated for lactate sensing, including in the presence of interferents such as ascorbic acid, uric acid, and acetaminophen. A multiplexed microneedle array containing digital micromirror device-produced microneedles was subsequently used for amperometric detection of glucose, lactate, and pH; detection of these analytes in complex media was shown [4]. More recently, digital micromirror device-produced hollow microneedles were modified with a working sensor, which was prepared with graphene ink and 4 (3-Butyl-1-imidazolio)-1-butanesulfonate) ionic liquid. Direct oxidation of fentanyl via square-wave voltammetry was shown; a detection limit of 27.8 μM was demonstrated using this approach [5]. Two photon polymerization has also been used to create hollow microneedles for biosensing; a porous carbon electrode created using interference lithography was used for potassium ion sensing in the presence of interfering sodium ions [6]. In another study, nitrogen-incorporated ultrananocrystalline diamond coatings were deposited on Ti –6Al–4V alloy microneedles using microwave plasma enhanced chemical vapor deposition; dopamine and uric acid were electrochemically detected in an in vitro study [7]. These studies indicate that microneedles may have utility for minimally invasive detection of analytes in a real time manner. Benefits and disadvantages of the microneedle-based sensing approach as well as efforts needed for clinical translation of microneedle-based sensing technology will be considered.