We report a new easier method for the quantitative analysis of sodium in human sweat. To the best of our knowledge this is the first time this has been done successfully in a real-time manner. We consolidate sweat stimulation, collection and analysis functions into a single method. This temporal data opens up new possibilities in the study of human physiology, broadly applicable from assessing athletic performance and hydration levels to monitoring Cystic Fibrosis (CF) sufferers. Our compact Sodium Sensor Belt (SSB) consists of a sodium selective Ion Selective Electrode (ISE) integrated into a platform that can be interfaced with the human body during exercise. No skin cleaning regime or sweat storage technology is required as samples is continually wicked from skin to a sensing surface and on to a waste terminal via a fabric pump. After an initial equilibration period, a sodium plateau concentration was reached and monitored continuously. Atomic Absorption Spectroscopy (AAS) was used as a refe rence method, confirming accuracy. The plateau concentrations observed fell within expected literature ranges, further confirming accuracy. Daily calibration 2 repeatability (n=4) was ±3.0% RSD and over a three month period reproducibility was ±12.1% RSD (n=56). As a further application, we attempted to monitor the sweat of Cystic Fibrosis (CF) sufferers using the same device. We observed high sodium concentrations symptomatic of CF (~60mM Na + ) for 2 CF patients, with no conclusive results for the remaining patients due to their limited exercising capability. The real-time monitoring of hydration levels during physical exercise for health and performance purposes is a particularly promising application for the SSB at present.

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Molecular-logic based computation (MLBC) has grown by accumulating many examples of combinational logic gates and a few sequential variants. In spite of many inspirations being available in biology, there are virtually no examples of MLBC in chemistry where sequential and combinational operations are integrated. Here we report a simple alcohol-ketone redox interconversion which switches a macrocycle between a large or small cavity, with erect aromatic walls which create a deep hydrophobic space or with collapsed walls respectively. Small aromatic guests can be captured or released in an all or none manner upon chemical command. During capture, the fluorescence of the alcohol macrocycle is quenched via fluorescent photoinduced electron transfer switching, meaning that its occupancy state is self-indicated. This represents a chemically-driven RS Flip-Flop, one of whose outputs is fed into an INHIBIT gate. Processing of outputs from memory stores is seen in the injection of packaged neurotransmitters into synaptic clefts for onward neural signalling. Overall, capture-release phenomena from discrete supermolecules now have a Boolean basis.

Urea-calix[4]arenes 1 and 2 were synthesised and incorporated into ISE membranes for assessment as sensors for inorganic anions in water. 1 revealed a strong response to all anions following the Hofmeister selectivity order. For ISEs of 2, the response to a portion of the anion series was suppressed, increasing the margin of selectivity of nitrate over chloride, a common interferant of nitrate in fresh and marine water samples. The performance of ISEs containing 2 was compared to commercially available alkylammonium nitrate ion-exchange salts used for nitrate sensing. Our ISEs performed favourably in terms of sensitivity, linear range and LOD with an improved selectivity coefficient over chloride of log K NO 3 À Cl À pot of À3.4, an order of magnitude better than commercially available nitrate ISEs. The pre-conditioning of ISEs in nonprimary chloride salt was essential for obtaining these results.

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Novel solid contact iodide selective electrodes based on covalently attached 1,2,3 triazole ionic liquid (IL) were prepared and investigated in this study. Triazole-based IL moieties were synthesized using click chemistry and were further copolymerized with lauryl methacrylate via a simple one step free radical polymerization to produce a "self-plasticized" copolymer. The mechanical properties of the copolymer are suitable for the fabrication of plasticizer-free ion-selective membrane electrodes. We demonstrate that covalently attached IL moieties provide adequate functionality to the ion selective membrane thus achieving a very simple, one component sensing membrane. We also demonstrate the presence of iodide as the counter-ion in the triazole moiety has direct influence on membrane's functionality. Potentiometric experiments revealed that each electrode displays high selectivity towards iodide anions over a number of inorganic anions. Moreover the inherent presence of the iodide in the membrane reduces the need for conditioning. The non-conditioned electrodes show strikingly similar response characteristics compared to the conditioned ones. The electrodes exhibited a near Nernstian behavior with a slope of -56.1 mV per decade across large concentration range with lower detection limits found at approximately 6.3x10 -8 M or 8 ppb . These all-solid state sensors were utilized for the selective potentiometric determination of iodide ions in artificial urine samples in the nanomolar concentration range.Potentiometric chemical sensors, with primary responses based on extraction and molecular recognition processes are a wellstudied and understood class of sensing devices. 1 Ion selective electrodes (ISEs) have been already widely used in a variety of fields such as clinical analysis, 2 process control 3 and environmental monitoring. 4 Ion selective membranes are typically composed of plasticized polymers, ion exchange salts, and one or more ionophores. Each constituent plays a specific role in the proper functioning of these membrane based ISEs. 5 Spontaneous and non-specific extraction of analyte ions from the sample into the membrane bulk is primarily suppressed due to the highly hydrophobic nature of the polymer backbone. Ideally, polymer matrix should provide a homogenous medium in which all active components can move freely. This strongly resembles the composition of liquid membrane electrodes since their sensing components were simply dissolved in an organic medium. However, the performance of polymer-based membranes can be drastically reduced if such sensors are used for the measurements of ions within more lipophilic environments in biological samples including undiluted whole blood. The cross contamination of chemical sensors coupled with leaching of the sensing components from the ion selective membrane into the sample fundamentally limited the applications of ISEs as a robust analytical tool for long-term trace level analysis. 6 Over the years, a number of approaches have been developed to minim...

Quality control (QC) measures are less prevalent in teaching laboratories than commercial settings possibly owing to a lack of commercial incentives or teaching resources. This article focuses on the use of QC assessment in the analytical techniques of high performance liquid chromatography (HPLC) and ultraviolet–visible spectroscopy (UV–vis) at undergraduate and master’s level. Data were collected over 2 semesters and the use of limits generated by staff were compared to the limits based on student data. This comparison enabled us to balance the learning of practical laboratory skills with providing sufficient incidences requiring troubleshooting and discussion on quality within the class. The QC limits chosen do not necessarily follow the perceived difficulty of an instrumental procedure. Staff-generated limits proved the most useful for the HPLC experiment, while broader student-based limits were deemed necessary for the simpler UV–vis experiment. Corrected calculations and computer templates were used in later QC charts as calculation errors were found to overshadow the identification of laboratory errors. The unique QC limits for any instrumental practical can be established and fine tuned in the same way as in the examples illustrated here.

Abstract-This paper details the development of a textile based fluid handling system with integrated wireless biochemical sensors. Such research represents a new advancement in the area of wearable technologies. The system contains pH, sodium and conductivity sensors. It has been demonstrated during on-body trials that the pH sensor has close agreement with measurements obtained using a reference pH probe. Initial investigations into the sodium and conductivity sensors have shown their suitability for integration into the wearable system. It is thought that applications exist in personal health and sports performance and training. I. INTRODUCTIONO date the majority of research in the area of wearable sensors has focused on the development of devices which measure physical parameters such as motion, respiration and heart rate [1]- [3]. However, textiles are often employed in sports applications to capture body fluids and wick them away from the skin surface. Such fabrics can be used as a platform for the development of biochemical sensors used to monitor the changing composition of fluids such as sweat under stress or exercise.Sweat is a clear hypotonic odorless fluid often described as an ultrafiltrate of plasma. Its major constituents are sodium, potassium, calcium, magnesium and chloride [4]. It is easily accessible with the sweat rate in human males during exercise measured in the region of 0.85 mg cm -2 min -1 for the lower back. Changes in the composition of sweat can be used to provide information on a person's physiological condition [5]. In addition, prolonged exercise can lead to dehydration and a change in the electrolyte concentrations in sweat. For elite athletes, a visible reduction in performance will occur for a 2 % drop in body weight due to dehydration. Further fluid loss can lead to symptoms such as irritability, headache, dizziness, cramps, vomiting, increased body temperature and heart rate, increased perceived work rate, reduced mental function, slower gastric emptying [6].