Abstract: A collection and testing cup for fluid characterization is disclosed. The cup has a lid assembly with a tamper evident closure; a cylinder that extends into the fluid in the collection cup, also with a tamper evident closure; a piston with a conduit and one-way valve through which a portion of the fluid can be forced into an isolation chamber separate from the main collection cup for testing. The lid assembly cylinder is configured with an aperture or passage near the bottom of the cylinder to allow a small portion of fluid to enter the lower portion of the cylinder from the collection cup chamber and a piston with a central conduit and valve initially positioned near the top of the cylinder adjacent to the lid.

Abstract: A system for the rapid characterization of multi-analyte fluids, in one embodiment, includes a light source, a sensor array, and a detector. The sensor array is formed from a supporting member into which a plurality of cavities may be formed. A series of chemically sensitive particles are, in one embodiment positioned within the cavities. The particles may be configured to produce a signal when a receptor coupled to the particle interacts with the analyte. Using pattern recognition techniques, the analytes within a multi-analyte fluid may be characterized.

Abstract: The present invention is directed to a novel method for measurement of glycated hemoglobin, as well as assay methods and processes that can be used outside the medical laboratory setting to determine the fraction of total hemoglobin that is glycated.

Abstract: The present invention provides a method and an apparatus for facilitating the creation and study of biological substrates. In particular, the present invention allows the location of materials deposited on a substrate to be identified, and communicated with great precision. This in turn allows additional biological materials to be deposited as probes over target locations. The present invention also allows for small regions of biological materials deposited on a substrate to be identified and repeatedly accessed, even when the biological substrate has been removed from the device originally used to review the region of interest and is then reinserted into the original device. Furthermore, the present invention allows a region of interest to be accurately located even using a machine that is different from the machine originally used to identify the region of interest.

Abstract: Analytical reagents and mass spectrometry-based methods using these reagents for the rapid, and quantitative analysis of proteins or protein function in mixtures of proteins. The methods employ affinity labeled protein reactive reagents having three portions: an affinity label (A) covalently linked to a protein reactive group (PRG) through a linker group (L). The linker may be differentially isotopically labeled, e.g., by substitution of one or more atoms in the linker with a stable isotope thereof. These reagents allow for the selective isolation of peptide fragments or the products of reaction with a given protein (e.g., products of enzymatic reaction) from complex mixtures. The isolated peptide fragments or reaction products are characteristic of the presence of a protein or the presence of a protein function in those mixtures. Isolated peptides or reaction products are characterized by mass spectrometric (MS) techniques.

Abstract: A leukocyte accumulation container having an opening, a sidewall portion and a bottom portion, part or all of the sidewall portion having a horizontal section area gradually increasing in a direction from the bottom portion towards the opening. A cytolytic agent is added to a solution of a platelet preparation or a solution of an erythrocyte preparation to solubilize platelets or erythrocytes in the solution of the preparation. The leukocyte accumulation container then is set on a centrifuge to accumulate the leukocytes on the bottom portion of the leukocyte accumulation container, and the leukocytes accumulated on the bottom portion are counted.

Abstract: The invention provides methods and compositions for detecting binding or unbinding of a molecule to a substrate. The molecule comprises a luminophore and the substrate comprises a semiconductor which acts as a luminescence quencher to provide distance-dependent quenching of the luminophore. Binding or unbinding of the molecule, which may be covalent or noncovalent, is detected as a decrease or increase, respectively, of the detectable luminescence of the luminophore.

Abstract: A biosensor, sensor array, sensing method and sensing apparatus are provided in which individual cells or randomly mixed populations of cells, having unique response characteristics to chemical and biological materials, are deployed in a plurality of microwells formed at the distal end of individual fibers within a fiber optic array. The biosensor array utilizes an optically interrogatable encoding scheme for determining the identity and location of each cell type in the array and provides for simultaneous measurements of large numbers of individual cell responses to target analytes. The sensing method utilizes the unique ability of cell populations to respond to biologically significant compounds in a characteristic and detectable manner. The biosensor array and measurement method may be employed in the study of biologically active materials, in situ environmental monitoring, monitoring of a variety of bioprocesses, and for high throughput screening of large combinatorial chemical libraries.

Abstract: An assay device for the detection of analyte in a sample, methods and immunoassay formats for performing an assay with or without the device, and methods for manufacturing the device are provided. The device is a continuous liquid flow channel having a proximal and a distal end, with a detection membrane in fluid communication with the distal end of the flow channel. Interspersed between the assay buffer and detection membrane, and continuous with the liquid flow channel, are a sample delivery means, one or more reservoirs containing the reagents necessary for conducting the assay, and, optionally, mixing or incubation reservoirs for combining the sample and reagents. The geometry of the liquid flow channel regulates the flow rate of the liquids through the channel, thereby controlling incubation, mixing and reaction time. The preferred detection membrane is an immunochromatographic test strip containing immobilized reagents.

Abstract: An apparatus and method for concentrating and measuring low levels of cells in biological samples. The apparatus, or concentration device, consists of two chambers with an optically level collection membrane intermediating between the chambers. The collection membrane filters the biological sample, trapping cellular elements of interest. A vacuum may be attached to the device to assist in filtration. The surface area of the collection membrane matches the view field of a standard imaging system and the device can be mounted on a standard microscope stage. All the cells in the sample volume are collected onto the membrane. The view field provides a fixed volumetric area for cell counting. Since the volume of sample tested is known, the total number of cells in the original sample may be calculated. The sample reservoir of the concentration device may also be used for sample preparation.

Abstract: Apparatus for calibrating a micro-array receiver comprising; a micro-array receiver including a substrate having coated a biologically active region with a composition including a first set of micro-spheres modified with a biological probe and containing an optical bar code generated from at least one colorant associated with the micro-spheres; and a calibration region associated with the substrate, the region being outside the biologically active region and having an area containing the optical bar code color.

Abstract: A fluid transfer and mixing collection assembly includes a base and a test media, an inlet check valve, and an outlet check valve carried by the base. A bladder containing a fluid and a flexible member are carried by the base between the check valves and are separated by a membrane. The flexible member is depressable to cause a pointed member extending from the flexible member to rupture the membrane, releasable to draw a sample fluid into an interior of the flexible member through the inlet check valve to mix with the fluid from the bladder, and depressable again to pump the mixed fluids out of the interior of the flexible member through the outlet check valve and be transferred to the test media.

Abstract: The invention provides a reagentless assay kit for analyte in a sample comprising a modular affinity assembly including at least one sensor unit comprising a ligand having binding affinity for the analyte (affinity module) operatively associated with a reporter probe (reporter module) responsive to changes in the sensor unit induced by analyte/receptor complex formation by transduction of a characteristic detectable signal. Assays employing the modular assembly are also provided.

Abstract: The invention is related to methods and apparatus that manipulate droplets in a microfluidic environment. Advantageously, embodiments of the invention manipulate droplets by controlling the electro-wetting characteristics of a surface with light, thereby inducing a gradient in the surface tension of a droplet. The gradient in the surface tension propels the droplet by capillary force. A variety of operations, such as transporting, joining, cutting, and creating can be performed. Advantageously, embodiments of the invention obviate the need to create a relatively large and complex control electrode array. A plurality of photoconductive cells or a layer of a photoconductive material selectively couples an electrode carrying an electrical bias to otherwise floating conductive cells in response to a beam of light. The electrical bias applied to the conductive cell generates a localized electric field, which can change the contact angle of the droplet, thereby permitting the droplet to be propelled.

Abstract: The present invention provides an apparatus and method for storing a particle-containing liquid. The storage apparatus comprises a microfluidic convoluted flow channel having a plurality of particle capture regions. The storage channel is preferably an isotropic spatially periodic channel. Sedimented particles can be resuspended following storage. This invention further provides a microfluidic analysis cartridge having a convoluted storage channel therein. The sample analysis can use optical, electrical, pressure sensitive, or flow sensitive detection. A plurality of analysis channels can be included in a single cartridge. The analysis channels can be joined to reagent inlets for diluents, indicators or lysing agents. A mixing channel can be positioned between the reagent inlet and the analysis region to allow mixing and reaction of the reagent. The cartridge can include additional valves and pumps for flow management.

Abstract: An optical assaying method and system having a movable sensor is described. In one aspect, the present invention is a sensing system having a rotating sensor disk coated with indicator dyes sensitized to a variety of substances. In this configuration the sensing system further includes a detector for sensing spectral changes in light received from one or more of the indicator dyes. In another aspect, the present invention is a sensing system having a surface plasmon resonance sensor disk having grooves extending radially from a center of the disk. In yet another aspect, the present invention is a sensing system including a diffraction anomaly sensor disk having a dielectric layer that varies in thickness. The present invention allows for construction of an inexpensive sensing system that is capable of easily detecting a variety of substances either in a sample or a surrounding environment.

Abstract: There is provided according to the invention an apparatus for the performance of photometric assays comprising: 1. A housing; 2. A plurality of translucent capillaries each being sealed at one end; 3. Means to provide each capillary with photonic isolation from a neighbouring capillary; and 4. Optical instrumentation and circuitry adapted to read an optical response or event in each capillary.

Abstract: A device for rapidly collecting tissue samples from organisms serves as a reaction chamber. It includes a solvent used to extract the analyte, a filter, and optional bioconcentrators. The filtered suspension is irradiated with a predetermined wavelength and the emitted, scattered, or reflected photons transmitted to a detector that identifies and quantifies the analyte. The bioconcentrators may consist of antibodies and colloidal metal nanoparticles that enhance emission of Raman signal frequencies by analytes bound to the antibodies. Alternatively, the device may contain only the extraction solvent and a filter.

Abstract: A surface plasmon resonance enzyme sensor including a sensing part 6 having an optically transparent base 1, a thin metal film 2 made of gold or silver, and a film 4 provided on the metal thin film 2 causing electron transfer reaction with both the thin metal film and the enzyme is provided.

Abstract: The present invention provides continuous strips of testers in an individually-sealed water-impermeable packaging which maintains the testers in a sterile condition until used. The subject testers include a test strip sensor integrated with a microneedle for accessing and collecting a sample of physiological fluid and for measuring a chemical characteristic, such as target analyte concentration, of the sampled fluid. The present invention further provides cassettes of the subject strips for removable engagement with a meter for individually dispensing the testers and for facilitating the analysis of the sampled fluid. Also provided by the present invention are systems which include the subject strips and cassettes and such a meter. Methods of using the strips and cassettes are also provided, along with kits for practicing the subject methods.

Abstract: Devices for determining the concentration of an analyte in a physiological sample are provided. The subject devices include a calibration means, at least one light source, a photometric detector array having at least one calibration detector and at least one other detector. The at least one calibration detector is capable of detecting a calibration mark from an analyte concentration measurement device container for calibrating the analyte concentration determination device. The at least one other detector is used for detecting reflected light from an analyte concentration measurement device associated with the analyte concentration determination device. The means for calibrating a component, aspect or feature of the analyte concentration determination device is based on the calibration mark. The subject invention also includes methods for calibrating a component, aspect or feature of a subject device based on the detected calibration mark. Also provided are kits for use in practicing the subject methods.

Abstract: The presence of carcinogens in air, soils, and other areas is detected by combining liquid-assisted air sampling with means for testing liquid samples for mutagenicity. Hazardous or illicit substances or pathogens which may be buried in the ground or otherwise concealed or present in contaminated food at various stages of food processing are detected using a two-line probe such that one of the lines directs exhaust air from the sampler onto suspect surfaces so as to dislodge and blow off droplets, particles or insects therefrom while the other line draws some of them into the sampler. Variants of said two-line probe can also serve to collect lead, hexavalent chromium or other harmful substances and bacterial, fungal or viral pathogens from crumbling walls or floors. Liquid-assisted air sampling can also serve to capture disease-transmitting insects and detect and identify insect-borne pathogens.

Abstract: A method for hemoglobin determination is described which includes the steps of introducing a sample of undiluted whole blood by capillary action into a disposable microcuvette having at least one cavity for receiving the sample. The cavity includes a dry essentially non-hygroscopic hemolysing agent, which is dissolved by the blood, hemolyses the red blood cells and releases the haemoglobin contained in the blood cells. A first absorption measurement at a wavelength range 490-520 nm is then performed directly on the sample in the microcuvette, and a second absorption measurement is performed to compensate for background interference.

Abstract: An automated analyzer which analyzes a sample which might have been affected by carryover, judges the effect of carryover from the analytical value, and indicates the result. The automated analyzer also performs analysis on a specific inspection item necessary for a sample which might have been affected by carryover from its preceding sample and modifies the result of analysis of said sample according to the analytical value.

Abstract: The invention discloses a method for determining the volume of individual red blood cells or other particles that are suspended in liquids. The sample is disposed into an optical cuvette suitable for microscopic analysis. An absorbing dye is added that does not leak into the cells, and that is able to absorb light at wavelengths that are only weakly absorbed by the cells. The cell volume is determined using transmitted light intensity values measured (i) in a first area comprising a single cell, (ii) in a second area close to that cell, and (iii) in said second area, after changing the cuvette thickness by a known amount.

Abstract: A device and method for filtering a biologically derived sample and for mixing the sample with a reagent, comprising a fluid container defining a reservoir compartment and including a container outlet, a filter and a fluid flow-through matrix disposed in a flow path between the reservoir compartment and the container outlet. Water-soluble, dried reagent is retained on the matrix. Means is provided for urging sample in an aqueous liquid in the reservoir compartment through the filter and matrix and out the container outlet. Pressure is applied to the sample in an aqueous liquid in the reservoir compartment to cause the sample to flow in liquid through the filter and matrix and out of the container for analysis.

Abstract: Apparatus or systems which employ luminescence-quenching to produce a signal indicative of oxygen concentration.

Abstract: The invention discloses a method for determining the volume of single red blood cells or other particles that are suspended in liquids. The sample is disposed into an optical cuvette suitable for microscopic analysis. A fluorescent dye is added that does not leak into the cells, and that is able to absorb excitation light and emit fluorescence light at wavelengths that are only weakly absorbed by the cells. The cell volume is determined using fluorescence intensity values measured (i) in a first area comprising a single cell, (ii) in a second area close to that cell, and (iii) in said second area, after changing the cuvette thickness by a known amount.

Abstract: A fluid transfer and mixing collection assembly includes a base and a test media, an inlet check valve, and an outlet check valve carried by the base. A bladder containing a fluid and a flexible member are carried by the base between the check valves and are separated by a membrane. The flexible member is depressable to cause a pointed member extending from the flexible member to rupture the membrane, releasable to draw a sample fluid into an interior of the flexible member through the inlet check valve to mix with the fluid from the bladder, and depressable again to pump the mixed fluids out of the interior of the flexible member through the outlet check valve and be transferred to the test media.

Abstract: Devices and methods for determining the concentration of an analyte in a physiological sample are provided. The subject devices are meters characterized by having an internal structure that includes a test strip selecting element having a continuously reduced cross-sectional area configured to select a single test strip at a time and means for determining the concentration of an analyte in a physiological sample applied to the selected test strip. In the subject methods for containing at least one test strip and dispensing a single test strip at a time, a meter having at least one test strip contained therein is provided. The meter is positioned with respect to the ground to cause the single test strip to move from a contained position to a dispensed position. The subject invention also includes kits for use in practicing the subject methods.

Abstract: A side-entry excitation arrangement is provided with a multi-channel analyte-separation device. In various embodiments, a plurality of channels are disposed in an array, with a laser disposed to direct an excitation beam of light along a beam path that crosses the longitudinal axes of the channels, so as to simultaneously irradiate a region of each of the channels. Devices of the invention can be useful, for example, in the separation and analysis of bio-molecules, such as DNA, RNA, etc.

Abstract: A method and apparatus for collecting a fluid specimen, locally analyzing the specimen to qualitatively detect specified chemical components at concentrations above threshold levels, and providing machine readable test results for facilitating data collection and reporting. The apparatus includes an assaying device comprised of a cup for collecting a fluid specimen and a cap carrying at least one test strip for visually reacting to one or more specified chemical components in the specimen. The cap also carries an aliquot delivery mechanism for forcing an aliquot of the fluid specimen onto the test strip. The assaying device is preferably configured to interact with a reader device capable of reading the reaction of the test strip to produce a data output.

Abstract: Apparatus or systems which employ luminescence quenching to produce a signal indicative of oxygen concentration. Components of such systems include: an airway adapter, sampling cell, or the like, having a sensor which is excited into luminescence with the luminescence decaying in a manner reflecting the concentration of oxygen in gases flowing through the airway adapter or other flow device; a transducer which has a light source for exciting a luminescable composition in the sensor into luminescence and a light sensitive detector for converting energy emitted from the luminescing composition as that composition is quenched into an electrical signal indicative of oxygen concentration in the gases being monitored; and subsystems for maintaining the sensor temperature constant and for processing the signal generated by the light sensitive detector.

Abstract: A field test kit for gunshot residue comprises a container having at least compartments separated by a barrier. A surface is tested by wiping it with a swab and placing the swab in a first compartment. The barrier is then breached, permitting reagent in the second compartment to flow onto the swab. The first compartment is transparent, and a color change will be observed if the reagent reacts with gunshot residue.

Abstract: Electrokinetic devices having a computer for correcting for electrokinetic effects are provided. Methods of correcting for electrokinetic effects by establishing the velocity of reactants and products in a reaction in electrokinetic microfluidic devices are also provided. These microfluidic devices can have substrates with channels, depressions, and/or wells for moving, mixing and monitoring precise amounts of analyte fluids.

Abstract: Emissive iridium (III) complexes suitable for use in an emissive layer of an OLED and having the structure: 1

Abstract: Compositions, methods, devices and kits for use in the calibration of coagulation tests. The control compositions comprise particles capable of aggregating in plasma and calcium ions which, when mixed with plasma, simulate the behavior of whole blood in a coagulation test. The methods comprise providing calcium ions and particles capable of aggregating in plasma, combining the particles and calcium ions with plasma to form a control composition, and applying the control composition to a coagulation test. The devices comprise a container having at least two compartments, with one compartment including particles that promote or induce aggregation of a protein or proteins in plasma, and the other compartment includes a solution of calcium ions. The kits comprise a control composition comprising a container of calcium ions, a container of particles capable of inducing aggregation of proteins in plasma, and one or more coagulation test devices.

Abstract: The present invention relates to a method for determining at least one parameter of samples of physiological liquids, to test devices which may be used in the method, to a holder comprising a plurality of such test devices, and to a measuring apparatus adapted to accommodate the holder and to be used in the method and to a system comprising the apparatus and the holder.

Abstract: Workstation, apparatuses and methods for the high-throughput synthesis, screening and/or characterization of combinatorial libraries. The invention relates to an array, which permits various high-throughput methods for synthesis, screening and/or characterization in the same array, without requiring sample transfer from the array. In a preferred embodiment, the synthesis, screening, and/or characterization steps are carried out in a highly parallel fashion, where more than one compound is synthesized, screened, and/or characterized at the same time. The invention may be practiced at the microscale. The array may comprise thermal channels, for regulating the temperature of the wells in the array. The wells of the array may comprise a membrane, which is used in various screening and characterization methods. The invention also relates to a covered array, comprising the array and an array cover, as well as an apparatus comprising the array, which comprises the array, an array cover and a stage.

Abstract: A method of using a chemical array reader, chemical array readers, and computer program products for use with a chemical array reader. The chemical array reader may include a holder to mount an array and hold the array at a reading position. A light system illuminates a mounted array when at a reading position. A detection system having a focal plane, to detect light from different regions across the array emitted in response to the illumination, when at the reading position, and which generates a resulting signal for each of the regions across the array. An autofocus system which detects and reduces offset between the different regions of an array at the reading position and a determined position of the focal plane.

Abstract: A weathering test method comprising making active oxygen and light simultaneously act on a test piece, a weathering test method comprising successive and/or alternate steps of making active oxygen and light simultaneously act on a test piece and making at least one of light, oxygen, and water to act on the test piece, and apparatus for carrying out the methods are disclosed. In evaluating weatherability of organic materials, articles made of organic materials or articles coated with organic materials, the methods and apparatus achieve acceleration of deterioration of test pieces to greatly reduce the testing time.

Abstract: According to one or more embodiments, the present invention is directed at many implementations of detectors utilized in bio-drives and in combination with a variety of different optical analysis discs or optical bio-discs. According to one embodiment of the present invention, the detector is a multi-segmented detector. According to another embodiment of the present invention, the detector is a radially long split detector. The detectors are segmented to implement noise-cancellation mechanism that enhances the overall signal-to-noise ratio. The detector embodiments produce clear and distinguishable signals that allow cell counting to be conducted efficiently in hardware. Another embodiment is a cost-efficient analyzer named a biological compact disc (BCD™) analyzer that comprises an optical disc drive and a controller into which is placed a field programmable gate array (FPGA) where all the digital logic is performed.

Abstract: A coaxial-drive centrifuge provides for contactless regulation of sample temperature. The sample is contained in a multi-station chemical-processing circuit that has a metal receptor at each station. On demand, a stationary inductor induces eddy currents in the receptor as it spins by. Dissipation of the eddy current heats the receptor and the surrounding sample. The receptor has a thermal sensor that provides an optical indication of the sample temperature. A stationary contactless reader reads the optical indication. A controller activates the inductor when the reading indicates an actual temperature below a predetermined target temperature. When heating is required, the inductor is pulsed as the receptor is aligned with a gap in the inductor. The chemical-processing circuit is designed for a specific series of chemical reactions, in this case, a polymerase chain reaction (PCR) is implement as an iterated series of three steps.

Abstract: The present invention recognizes that it can be desirable to have a sample receiving chamber integral to or engageable with a test platform, such as a test platform that includes a test strip. The sample receiving chamber is preferably separate or separable from the test platform, but that need not be the case. Preferably, a fluid flow actuating device or structure, such as a valve separates the sample receiving chamber from the test platform. The present invention provides such a device and methods of use. A first aspect of the present invention is a test device that includes a sample receiving chamber and a test platform that preferably includes a test element. The sample receiving chamber preferably engages the test platform and is optionally separable therefrom. A second aspect of the present invention is a method of detecting an analyte in a sample, including: providing a sample, contacting the sample with a test device and detecting the analyte in the sample.

Abstract: A multiwell plate scanner comprises a detector for measuring an attribute of a sample which is scanned continuously over wells of a multiwell plate. A signal obtained during the scan may be sampled and digitized based on detector position over the multiwell plate. The scanner is also disclosed for scanning microarrays, bio-chips and areas of samples not having physical separations. The scanner may be used in a high throughput screening system comprising a storage and retrieval module, a sample distribution module, a reagent distribution module, and a detector which incorporates the scanner. The screening system may further comprise a transport module and a data processing and integration module for transporting samples between the components of the system and for controlling system operation.

Abstract: A device for detection of one or more analytes in a sample is disclosed. The device can simultaneously detect and quantitate multiple analytes in a sample. The device comprises an eletromagnetic radiation generator having one or more chemical sensors thereon. The chemical sensor interacts with or reacts with specific analytes in a sample. The presence of an analyte is detected by a comparison of the spectroscopic properties of the chemical sensor in the absence and presence of the analyte. A method is also disclosed for the detection and quantitation of analytes using the device of the present invention. In addition, a method of making the device of the present invention is also disclosed.

Abstract: An analytical cell including a lightguide with a plurality of conduits filled with a migration medium. The medium, the lightguide and a surrounding medium have refractive indices selected such that light entering the lightguide is internally reflected within the lightguide to provide substantially uniform illumination of the conduits.

Abstract: A sensor which senses concentrations of a component of a fluid. In a dialysis system, the sensor can monitor the total ammonia and ammonium concentration in dialysate. The sensor has an optical indicator, such as an ammonia sensitive membrane, positioned in direct contact with the dialysate fluid when in use. The ammonia sensitive membrane has a variable optical indication, such as a variable color change, in relation to the concentration of ammonia in the dialysate. An optical reader reads the color change of the membrane to measure the total ammonia and ammonium concentration in the dialysate. The sensor can be used in the dialysis system to monitor the effectiveness of sorbants which remove ammonia/ammonium which is produced from an enzyme reaction with urea, the urea being removed from a patient during dialysis treatment.

Abstract: A sensing apparatus and methods for measuring or detecting an analyte present in a biological system are provided. The methods entail use of the sensing apparatus that contains a reporter system specific for the analyte of interest, where the reporter system is either affixed to a planar backing or attached to particles that are delivered to the superficial layers of the skin. The reporter system includes a reporting reagent that absorbs or emits a detectable radiation and is placed in communication with the analyte, or in communication with tissue or body fluids suspected of containing the analyte. The sensing apparatus is illuminated, and a radiation signal from the reporting reagent is measured or detected and then associated with the presence or quantity of analyte.

Abstract: A membrane capable of sensing gaseous phase ammonia is provided. The membrane includes a hydrophobic membrane layer that has a microporous structure and a pH sensitive dye embedded within the microporous structure such that the membrane is capable of calorimetrically sensing a change in ammonia with a high degree of sensitivity and responsiveness as applied to, for example, a change in ammonia dissolved in a dialysis solution during dialysis therapy.