Abstract: The present invention provides a pH sensing apparatus that includes a flexible polymer substrate, one or more amorphous iridium oxide film sensor electrodes disposed on the flexible polymer substrate, and a reference electrode corresponding to each amorphous iridium oxide film sensor electrode. Each reference electrode is disposed on the flexible polymer substrate in close proximity to the corresponding amorphous iridium oxide film sensor electrode. The amorphous iridium oxide film sensor electrodes provide a potential in reference to the reference electrodes that varies according to a pH of a substance contacting the amorphous iridium oxide film sensor electrodes and the reference electrodes.

Abstract: Micromachined reference electrodes for use in miniaturized electrochemical sensors, and methods for fabricating such reference electrodes and electrochemical sensors, for example, as a part of a microfluidic system, are disclosed. Electrochemical measurements allow for inexpensive detection of a wide variety of (bio-)chemical compounds in solution. The reference electrode is one of the main parts of an electrochemical cell. The reference electrode, from which no current is drawn, has a stable, constant potential.

Abstract: A method for preventing the formation of gas bubbles inside a high pressure reference electrode in the electrolyte-filled section, and thus eliminating the gas bobble effect on the electrical continuity, was disclosed. One or more thin solid rods or tubes are inserted into the internal electrolyte-housing tube and the thin rods or tubes alter the surface tension of the gas bubbles so that the bubbles are unstable in the middle of the liquid electrolyte. Compared with the fibre wicks or porous powder used by previous researchers to ensure the electrical continuity, the thin tubes or rods are easy to handle and easy to clean. This method may also be used in other systems that contain a liquid-filled vertical or sloped tube (e.g., a pH electrode) to prevent the formation of gas bubbles in the liquid-filled section of the tube.

Abstract: The invention comprises portable, rugged and relatively compact electrochemical cells. Each may be removably and nondestructively secured to one surface of a substrate of indefinite size. In-situ electrochemical measurements may be made on portions of existing structures such as ships, bridges, or buildings. An electrochemical cell is disclosed which comprises an analytical chamber which can be utilized with either on-board or external potentiostats. The electrochemical cell has a mounting means which permits the cell to be secured to substrates with irregular surface morphology and to horizontal, vertical or intermediately oriented surfaces. The electrochemical cell provides a means to control the temperature of the electrolyte and the substrate area of interest to permit more accuract and consistent elecrochemical measurements.

Abstract: This invention provides a reference electrode that can be downsized and stable in voltage. The reference electrode in accordance with this invention is a reference electrode that does not require an internal aqueous solution such as a KCl aqueous solution and comprises a metal body, a slightly soluble salt film that comprises a slightly soluble salt of the metal body and that coats the metal body and a hydrophobic ionic liquid that is arranged to make contact with both the slightly soluble salt film and a sample to be measured.

Abstract: A reference half-cell for application in an electrochemical sensor, comprising a housing, in which a chamber containing a reference electrolyte is formed, wherein the reference electrolyte (5, 105) is in contact with a medium surrounding the housing via a liquid junction arranged in a wall of the housing, wherein the liquid junction comprises a porous diaphragm, especially a porous ceramic diaphragm, and wherein the diaphragm has, at least partially, a coating, which comprises at least one metal.

Abstract: The present invention relates to a device for sensing a target chemical. The device includes a flexible, non-planar substrate; a printed, solid-state sensing element comprising a chemical sensing material which produces an electrical signal upon interaction with the target chemical; a first printed electrode comprising a first conductive composition; and a second electrode comprising a second conductive composition. The first and second electrodes are electrically isolated from one another, and one or both of the first and second electrodes is in electrical contact with said sensing element. The first and second electrodes and the sensing element collectively form an electrochemical sensor which is coupled to the flexible, non-planar substrate. Medical devices comprising the device of the present invention and methods of making a device for sensing a target chemical are also disclosed.

Abstract: A miniature, lightweight, inexpensive, environmental monitoring system containing a number of sensors that can simultaneously and continuously monitor fluorescence, absorbance, conductivity, temperature, and several ions. Sensors that monitor similar parameters can cross-check data to increase the likelihood that a problem with the water will be discovered.

Abstract: Disclosed is an electrode system capable of more accurately measuring properties of solutions using a porous platinum electrode.

Abstract: An apparatus and method of simultaneous spectroelectrochemical analysis is disclosed. A transparent surface is provided. An analyte solution on the transparent surface is contacted with a working electrode and at least one other electrode. Light from a light source is focused on either a surface of the working electrode or the analyte solution. The light reflected from either the surface of the working electrode or the analyte solution is detected. The potential of the working electrode is adjusted, and spectroscopic changes of the analyte solution that occur with changes in thermodynamic potentials are monitored.

Abstract: It is an object of the present invention to provide a gas concentration detection apparatus that is capable of forming an accurate activity judgment when a gas concentration detection cell begins to detect gas concentration with high accuracy. When warm-up begins at time t0 in a NOx concentration detection apparatus that achieves NOx concentration detection with a NOx sensor cell after excess oxygen is discharged by an oxygen pump cell, a NOx sensor cell output begins to rise at time t1. Subsequently, at time t2, an oxygen pump cell output begins to rise. An inflection point appearing in the NOx sensor cell output is then located. At time t5 at which the inflection point appears, an activity judgment about the NOx sensor cell is formed.

Abstract: A long-term, reliable high pressure reference electrode for high temperature applications was disclosed. This reference electrode has inner and an outer liquid junction plugs. The inner plug provides the function of restraining the outflow of the internal reference electrolyte. The outer plug is chemically and mechanically robust in the external fluid where the reference electrode is used and protects the inner plug from the mechanical and chemical attacks by the harsh external fluid. Therefore, the inner plug can be selected from many of the well-characterized liquid junction plugs used in regular low temperature reference electrodes, without the need for the inner plug to be chemically and mechanically stable in the external fluid, as long as it has the thermal stability. A method for preventing the formation of gas bubbles inside a high pressure reference electrode in the electrolyte-filled section, and thus eliminating the gas bobble effect on the electrical continuity, was also disclosed.

Abstract: A differential pH probe design uses a container having an outer surface and an inner volume, where the inner volume is divided into a first chamber and a second chamber. A first pH-sensitive area is located on the outer surface of the first chamber where the first pH-sensitive area is configured to be exposed to a sample. A second pH-sensitive area is located on the outer surface of the second chamber where the second pH-sensitive area is shielded from the sample and is exposed to a buffer solution. A first electrode is configured to detect a first voltage in the first chamber and a second electrode is configured to detect a second voltage in the second chamber. Circuitry is coupled to the first and second electrodes and configured to process the first voltage and the second voltage to determine a pH of the sample.

Abstract: In an oxygen sensor control apparatus, a CPU obtains a correction coefficient for calibrating the relation between output value of an oxygen sensor and oxygen concentration when a fuel cut operation is performed. When the amount of scavenging air (total supply amount of air) becomes equal to or greater than a predetermined amount in each fuel cut period, the CPU calculates an average output value Ipav from a plurality of output values (concentration corresponding values) Ipr of the oxygen sensor, from which values deviating from a predetermined range R1 have been removed. Subsequently, the CPU averages the values obtained in a plurality of fuel cut periods to thereby obtain a plural-time average output value Ipavf. The CPU obtains a correction coefficient for correcting the actual output value Ip of the oxygen sensor 20 on the basis of the Ipavf value and a previously set reference output value.

Abstract: Methods and systems for measuring the oxidation-reduction potential of a fluid sample are provided. The system includes a test strip with a sample chamber adapted to receive a fluid sample. The sample chamber can be associated with a filter membrane. The test strip also includes a reference cell. The oxidation-reduction potential of a fluid sample placed in the sample chamber can be read by a readout device interconnected to a test lead that is in electrical contact with the sample chamber, and a reference lead that is in electrical contact with the reference cell. Electrical contact between a fluid sample placed in the sample chamber and the reference cell can be established by a bridge. The oxidation-reduction potential may be read as an electrical potential between the test lead and the reference lead of the test strip.

Abstract: Oxidation/reduction measurement is described. An aspect provides an oxidation/reduction quantification method, including: receiving intermittent oxidizer/reducer reference measurements from one or more reference sensors; receiving one or more substantially continuous oxidizer/reducer-related measurements from one or more corroboration sensors; and processing the one or more substantially continuous oxidizer/reducer-related measurements with the intermittent oxidizer/reducer reference measurements to generate substantially continuous representative oxidizer/reducer measurements. Other aspects are described.

Abstract: An electrochemical sensor is provided that includes a housing having an outer wall, an axial bore circumscribed by the outer wall, and a barrier wall that aids in defining a reference cavity. The housing further including a plurality of cross members in spaced relation to one another disposed between the axial bore and the outer wall, each cross member defining an aperture. A junction plug is disposed at the distal end of the housing. The junction plug comprises a porous material that enables ionic flow through the junction plug. The sensor enables ionic communication between the target fluid and the reference electrode within the reference cavity through the apertures of the plurality of cross members. In this manner, the sensor provides generally a long, tortuous flow path, or salt bridge, between the target fluid and the reference electrode, resulting in a high resistance factor for the sensor.

Abstract: The invention comprises portable, rugged and relatively compact electrochemical cells. Each cell has the ability to be removably and nondestructive secured to one surface of a substrate of indefinite size. In-situ electrochemical measurements may be made on portions of existing structures such as ships, bridges, or buildings. An electrochemical cell comprises an analytical chamber which can be utilized with potentiostats. An electrochemical cell is a self-contained portable probe comprising an electrochemical cell, an electronics component and a fluid handling component. Said probe is capable of performing electrochemical measurements by itself without the use of an external potentiostat, such as monitoring corrosion, effectiveness, or integrity of conductive and nonconductive coatings on bare and coated metallic or conductive substrates.

Abstract: Disclosed is a method and apparatus for detecting the concentration of a lipophilic analyte of interest in a complex sample matrix. The method comprises extracting the analyte of interest from said sample into an organic solvent comprising a dissolved electrolyte; providing a free radical species, preferably a free oxygen radical species, in said organic solvent; reacting the Canalyte of interest with said free radical species; and performing a measurement to detect the concentration of the free radical-reacted analyte reaction product.

Abstract: Temperature compensation for ion-selective electrodes is obtained by positioning a temperature-measuring element in a chamber of limited thermal mass which is in thermal contact with the measuring electrode filling solution but is thermally isolated from other filling solutions in the electrode. In a preferred embodiment, the temperature-measuring element comprises a thermistor enclosed within thin flexible tubing; the electrical leads of the thermistor are forced against a segment of the inner wall of the tubing by an elongated strand of material abutting the thermistor to enhance heat transfer with the thermistor.

Abstract: A reference electrode having a casing with an inner cavity successively filled with a paste constituting an active material and a porous material impregnated with an electrolyte solution. The projecting end of a silver wire is embedded in the paste at the bottom of the inner cavity. The paste is constituted of a powder of a silver compound and of the alkaline electrolyte solution. The silver compound is any insoluble silver salt or oxide containing the negative ion of the electrolyte solution. The impregnated porous material is preferably constituted by a plurality of mat separator pieces mechanically and compressed by a closing plug, closing the inner cavity and forming a porous liquid junction.

Abstract: Methods and systems for measuring the oxidation-reduction potential of a fluid sample are provided. The system includes a test strip with a sample chamber adapted to receive a fluid sample. The sample chamber can be associated with a filter membrane. The test strip also includes a reference cell. The oxidation-reduction potential of a fluid sample placed in the sample chamber can be read by a readout device interconnected to a test lead that is in electrical contact with the sample chamber, and a reference lead that is in electrical contact with the reference cell. Electrical contact between a fluid sample placed in the sample chamber and the reference cell can be established by a bridge. The oxidation-reduction potential may be read as an electrical potential between the test lead and the reference lead of the test strip.

Abstract: Methods and systems for measuring the oxidation-reduction potential of a fluid sample are provided. The system includes a test strip with a sample chamber adapted to receive a fluid sample. The sample chamber can be associated with a filter membrane. The test strip also includes a reference cell. The oxidation-reduction potential of a fluid sample placed in the sample chamber can be read by a readout device interconnected to a test lead that is in electrical contact with the sample chamber, and a reference lead that is in electrical contact with the reference cell. Electrical contact between a fluid sample placed in the sample chamber and the reference cell can be established by a bridge. The oxidation-reduction potential may be read as an electrical potential between the test lead and the reference lead of the test strip.

Abstract: The present invention relates to a thin-film pseudo-reference electrode and method for the production thereof, wherein the pseudo-reference electrode is made up of a substrate formed by an oxidized silicon wafer on which a single thin film of silver, which has a thickness comprised between 100 nm and 1500 nm, is deposited directly by means of the sputtering technique.

Abstract: This disclosure relates to sulfur sensors that utilize sensing materials that can be used to detect a wide range of concentrations including ultra low concentrations of sulfur in liquids, such as below even 15 ppm. The sulfur sensors comprise a sensing electrode having a material that contributes an electronic output to the analysis and a material that contributes an ionic output to the analysis.

Abstract: An electrode comprising: a least a first, preferably cylindrical, glass body, in which at least a first chamber is formed; at least a first electrolyte, which is located in the first chamber; at least a first potential-forming element, which is arranged in the chamber, and forms a first potential when contacted by the first electrolyte; at least a first closing element, which is axially fixed in the first chamber for enclosing the first electrolyte and the first potential-forming element and sealedly closes the first chamber; wherein, additionally, the first closing element is conductive, the first potential-forming element conductingly contacts the first closing element, and the electrode furthermore includes at least a first electrical conductor, which electrically contacts the first closing element on the side of the first closing element facing away from the first electrolyte.

Abstract: The invention provides an electrochemical sensor comprising an electrode assembly which comprises at least two electrodes, one of the electrodes comprising a metal species capable of catalysing the oxidation of hydrogen and/or methane. The sensor may be used in the detection and quantification of hydrogen and/or methane in exhaled breath, for example as a means of diagnosing lactose malabsorption or lactose intolerance.

Abstract: The present invention provides methods and apparatuses for analyte detection.

Abstract: An electrochemical sensor is provided that includes a housing having an outer wall, a plurality of longitudinal chambers disposed within the outer wall, and a reference chamber housing a reference electrode. Ionic communication between the target fluid and the reference electrode must pass sequentially through each of longitudinal chambers from a first longitudinal chamber to the reference chamber. In this manner, the sensor provides generally a long, tortuous flow path, or salt bridge, between the target fluid and the reference electrode, resulting in a high resistance factor for the sensor.

Abstract: A microfabricated liquid junction reference electrode that can be integrated with microfabricated chemical or electrical sensors, which electrode is an M/MX type reference electrode comprised of a metal and a metal salt, as well as a X? Containing Ionic Liquid having a constant activity of X? and a porous thin-film membrane impregnated with a Hydrophobic Ionic Liquid.

Abstract: A reference electrode traps silver ions and chloro complex ions leaching to an internal filling solution so that the blocking of the liquid junction can be prevented. A silver/silver chloride electrode can be provided as an internal electrode in an internal filling solution; and a tube which houses, in order from top to bottom, the internal electrode, an inorganic cation exchanger for trapping silver ions and/or chloro complex ions from leaching from the internal electrode, and a ceramic member for preventing the diffusion of the silver ions and/or the chloro complex ions to the internal filling solution.

Abstract: A potentiometric sensor with suppressed leak current on the surface of an electrode and improved for a dynamic range and a response speed, in which a redox compound is immobilized through insulative molecules on the surface of a gold electrode, and a current between a source and drain of an insulated gate field-effect transistor along with reaction between an oxidized substance or a reduced substance produced by the reaction of a measured substance in a sample solution injector for supplying the sample solution containing the measured substance and an enzyme and a redox compound on the surface of the gold electrode, is monitored on real time to measure the change of the surface potential.

Abstract: The invention provides a reference electrode including a liquid electrolyte containing water, a water soluble organic compound with molecular size and boiling point are both greater than water, and an ionic salt; a solid crystal of the ionic salt in the liquid electrolyte; a metal/metal salt complex layer in contact with the liquid electrolyte; an leading wire connected to the metal/metal salt complex layer; an insulation case for containing the liquid electrolyte; and a nano-porous junction material embedded in the insulation case for contacting the liquid electrolyte, wherein a pore size of the nano-porous junction material is greater than a cation diameter of the ionic salt but smaller than a molecular length of the water soluble organic compound. The solid crystal of the ionic salt is the sediment of part of the ionic salt because the amount of the ionic salt is more than its solubility in the liquid electrolyte.

Abstract: A low maintenance reference electrode has a liquid junction body with a multiplicity of micron-sized capillary channels extending through the body for transporting electrolyte to a test solution. A viscosity-increasing agent thickens the electrolyte to limit its flow to a rate on the order of microliters/day so that a few milliliters of electrolyte suffice to provide an extended electrode life.

Abstract: The present invention concerns a probe for measuring hydrogen concentration in molten metals comprising a probe body and a hydrogen sensor. The sensor structure is based on a sensor body having a wall within which a sealed cavity is defined. The cavity contains a solid reference material for generating a reference partial pressure of hydrogen within the cavity. At least a portion of the wall of the cavity is formed from a solid electrolyte material carrying a measurement electrode on a surface of the solid electrolyte outside the cavity and a reference electrode on a surface of the solid electrolyte within the cavity, exposed to the reference partial pressure of hydrogen. An electrical conductor extends from the reference electrode through the wall of the cavity to an external surface of the sensor body. The probe body comprises a chamber for receiving the sensor and a reference-signal connection for connecting to the electrical conductor when the sensor is received in the chamber.

Abstract: Disclosed is a sensor device (10) comprising a substrate (100) carrying a sensing element (110), and a metallization stack on said substrate for providing interconnections to said sensing element, the metallization stack comprising a plurality of patterned metal layers (130a-d) separated by insulating layers (120a-d), wherein a first metal layer (130c) comprises an electrode portion (16) conductively connected to the sensing element, and a further metal layer (130d) facing the first metal layer comprises a reference electrode portion (18), the electrode portion and the reference electrode portion being separated by a fluid channel (14) accessible from the top of the metallization stack. A method of manufacturing such a sensor device is also disclosed.

Abstract: A measurement device measuring a solution and including a reference voltage generating unit, a plurality of sensing units, a reading unit and a processing unit is disclosed. The reference voltage generating unit is disposed in the solution to generate a reference voltage. The sensing units are disposed in the solution to generate a plurality of output signals relating to the reference voltage. The reading unit outputs a reading signal according to one of the output signals. The processing unit generates a measuring signal according to the reading signals.

Abstract: A reference electrode, especially for a potentiometric measuring cell, comprising: a housing, which surrounds a housing interior, which contains a reference electrolyte and at least a part of a sensing system for sensing a potential of the reference electrode. The reference electrolyte is in contact with a medium surrounding the housing, especially a measured medium, via at least one bore traversing through a housing wall of the housing, and wherein the bore has an inner diameter of no more than 50 ?m at its narrowest point and a length of no more than 200 ?m.

Abstract: A flowing junction reference electrode comprising a liquid junction member matched with a filter. The junction member and the filter are situated between a reference electrolyte solution and a sample solution. An array of nanochannels spans the junction member and provides fluid communication between the electrolyte solution and the sample solution. The filter is configured to allow a greater flux of electrolyte than that associated with the junction member. Preferably, the number of pores is greater than the number of nanochannels. The filter is preferably configured to have pores with an inner diameter that is the same or less than the inner diameter of the nanochannels. In some embodiment, the resistance of the filter is made lower relative to the resistance of the junction member by selecting suitable length, number, and inner diameter size for the pores of the filter relative to the nanochannels of the junction member.

Abstract: A combination electrode, including: A first tube; a measuring membrane, which sealedly closes the first tube to form a measuring chamber; a second tube, which surrounds the first tube and is connected borderingly with the first tube to form an annular reference chamber; a buffer solution located in the measuring chamber; an electrolyte solution located in the reference chamber; a first tapping electrode in contact with the buffer solution; and a second tapping electrode in contact with the electrolyte; wherein, additionally, arranged in the reference chamber is an axially shiftable, annular, sealing element, which bounds the volume occupied by the electrolyte solution, the sealing element is biased by means of an electrically conductive, elastic, deformation element, which surrounds the first tube, and the second tapping electrode is electrically connected with the deformation element, in order to tap the potential of the second electrode via the deformation element.

Abstract: An electrochemical sensor is provided that includes a housing defining a cavity for a reference electrolyte and defining an opening to the cavity configured to be proximate to a target fluid. The sensor further includes a junction plug comprising a porous material and a cross member impermeable to a target fluid positioned between the junction plug and the cavity. The cross member is disposed proximate to the junction plug, defining an aperture to enable electrochemical communication between the target fluid and the reference electrolyte.

Abstract: An electrochemical sensor is provided that includes a housing having an outer wall, a plurality of longitudinal chambers disposed within the outer wall, and a reference chamber housing a reference electrode. Ionic communication between the target fluid and the reference electrode must pass sequentially through each of longitudinal chambers from a first longitudinal chamber to the reference chamber. In this manner, the sensor provides generally a long, tortuous flow path, or salt bridge, between the target fluid and the reference electrode, resulting in a high resistance factor for the sensor.

Abstract: Disclosed herein is a reference electrode including an electrolyte containing an optically-active material, including: an electrode body provided at an end thereof with an electrolyte separation membrane and charged therein with an optically-active material and an electrolyte solution; an inner electrode disposed in the electrode body to be immersed in the electrolyte solution; and an absorbance measurement probe for transmitting light to the electrolyte solution and collecting reflected light waves, which is disposed in the electrode body to be immersed in the electrolyte solution. Since the concentration of an electrode reaction material, such as Cl?, in the electrolyte is calculated using the absorbance of the electrolyte solution containing the optically-active material, the change in potential of the reference electrode can be properly corrected even when the reference electrode is exposed to a test environment for a long period of time and thus the concentration of the electrolyte changes.

Abstract: The present invention is generally directed to devices and methods for sensing a variety of biologically-related substances. In a device aspect, the present invention is directed to a multilayer device for sensing metal ions, biological molecules, or whole cells. The device comprises: a) one or more cavities that provide for the introduction of a sample to be analyzed and one or more channels that provide for exit of the sample, or one or more channels that provide for the introduction and exit of the sample; b) one or more single-walled carbon nanotubes presented to the one or more cavities or one or more channels; c) a plurality of electrodes electrically connected to the one or more single-walled carbon nanotubes; and, a reference gate electrode presented to the one or more cavities or one or more channels. In a method aspect, the present invention is directed to a method for sensing species such as a metal, biological cells, and one or more biological molecules using the device.

Abstract: An electrochemical sensor includes a dielectric substrate and a conductive layer formed on a surface of the substrate. The conductive layer includes a working electrode, an electrode lead and a connecting arm connecting the working electrode to the electrode lead. A dielectric layer is positioned over the conductive layer. The dielectric layer has an aperture exposing the working electrode and a portion of the connecting arm. The working electrode, electrode lead and connecting arm may be formed by laser ablation technique to provide precise working electrode sensor parameters.

Abstract: An ion sensor includes a sensor main body having a channel for a sample and an opening connected to the channel, a responsive portion which is filled in the opening and selectively responds to a specific ion, an electrode which has a ring shape, is set such that a central axis of the ring is substantially perpendicular to a central axis of the channel, and senses the response, and an output terminal which is formed out of one metal plate out of which the electrode is formed, has a pin shape, and is held by the sensor main body such that an axis extends along a direction substantially perpendicular to the central axis of the channel and the central axis of the ring.

Abstract: Micromachined reference electrodes for use in miniaturized electrochemical sensors, and methods for fabricating such reference electrodes and electrochemical sensors, for example, as a part of a microfluidic system, are disclosed. Electrochemical measurements allow for inexpensive detection of a wide variety of (bio-)chemical compounds in solution. The reference electrode is one of the main parts of an electrochemical cell. The reference electrode, from which no current is drawn, has a stable, constant potential.

Abstract: In order to realize an accurate electrochemical measurement without a peak caused due to a silver chloride complex ion, an electrochemical measurement electrode of the present invention which measures an electrochemical active substance in a sample solution containing a chloride ion includes (i) a working electrode, (ii) a reference electrode made of silver and silver chloride, and (iii) a silver ion capturing material which captures a silver ion out of a silver chloride complex ion generated in the reference electrode.

Abstract: A wastewater analysis sensor cartridge (10) according to the invention is intended to be used only once. It has a liquid-tight housing (20), which contains at least one electrochemical sensor element (30, 32) and at least one reference element (56). Furthermore, the housing (20) contains a sensor element electrolyte tank (40,42) and a reference element electrolyte tank (44). The ion-sensitive membranes (31, 33) of the sensor elements (30, 32) and the housing (20) consist of plastic.

Abstract: A flowing junction reference electrode comprising a liquid junction member matched with a filter. The junction member and the filter are situated between a reference electrolyte solution and a sample solution. An array of nanochannels spans the junction member and provides fluid communication between the electrolyte solution and the sample solution. The filter is configured to allow a greater flux of electrolyte than that associated with the junction member. Preferably, the number of pores is greater than the number of nanochannels. The filter is preferably configured to have pores with an inner diameter that is the same or less than the inner diameter of the nanochannels. In some embodiment, the resistance of the filter is made lower relative to the resistance of the junction member by selecting suitable length, number, and inner diameter size for the pores of the filter relative to the nanochannels of the junction member.