Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
  • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
  • G01N27/06—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a liquid
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
  • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
  • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
  • G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
  • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
  • G01N27/28—Electrolytic cell components
  • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
  • G01N27/333—Ion-selective electrodes or membranes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/18—Water
  • G01N33/1813—Specific cations in water, e.g. heavy metals

Definitions

• the present invention relates to an apparatus and method for detecting ions of heavy metallic element through ion recognizing molecule or ionophores without using reference electrode.
• Heavy metals such as mercury and lead are considered fatal to human.
• Heavy metals in the environment get into human through food especially fish, and from drinking contaminated water. When consumed by fish in the form of contaminated food or directly taken from polluted water the heavy metals are retained in human body.
• the present invention proposes selective lead (II) ion sensor based on ionophore without using reference electrode.
• the lead (II) ion recognizing molecule is immobilized onto ion sensing channels sandwiched by conductive pads for electrical communication.
• the lead ionophore is secured on the channel with low impedance polymeric matrix such as ethyl cellulose.
• the baseline conductivity of the channel is adjusted by adding sufficient amount of conductive particles such as carbon nanotubes.
• Ion recognizing molecules or ionophores are most widely used in ion-detecting chemical sensors to achieve selectivity on target ion.
• the recognizing agents are almost always neutral large molecules showing preferential binding to specific ion.
• ionophore selectively holds on the target ion and "carries" the ions across polymeric sensing matrix.
• the sensing electrode either an ion selective electrode (ISE) or ion sensitive field effect transistor (ISFET), is coupled to a reference electrode to measure potential difference between the two electrodes.
• ISE ion selective electrode
• ISFET ion sensitive field effect transistor
• the present invention provides an apparatus (100) for detecting ions of heavy metallic element comprising at least one polymeric binder (102) to secure and immobilize lead (II) ion recognizing molecule onto ion sensing channels.
• the apparatus (100) comprising conductive filler particles (104) to reduce impedance across channel and adjust baseline of electrical conductivity; ion recognizing molecule or ionophores (106) with preferential binding to bind lead (II) ion selectively in the presence of interfering ions; and at least one channel on a substrate (108) in communication with at least two electrodes (110) to allow passage of current across channel through at least one channel on substrate (108) in communication with at least two electrodes (110).
• a further aspect of the present invention provides a method (200) for detecting ions of heavy metallic element using ion recognizing molecule or ionophores with preferential binding to specific ion.
• the method comprising steps of securing and immobilizing lead (II) ion recognizing molecule onto ion sensing channels (202); reducing impedance across channel and adjusting baseline of electrical conductivity (204); binding lead (II) ion selectively in the presence of interfering ions (206); and allowing passage of current across channel through at least one channel on substrate in communication with at least two electrodes (208).
• the method for securing and immobilizing lead (II) ion recognizing molecule onto ion sensing channels (202) further comprises carrying selected ions across polymeric sensing matrix.
• the method for reducing impedance across channel and adjusting baseline of electrical conductivity (204) further comprises adding conductive particles to reduce impedance across channel beyond limit of organic binder.
• the method for allowing passage of current across channel through at least one channel on substrate in communication with at least two electrodes further comprises measuring differential conductance and analyte concentration to determine response and sensitivity of sensor (302); and plotting conductance against analyte concentration to determine conductance of channel (304).
• FIG. 1 illustrates lead (II) sensor without using reference electrode.
• FIG. 2 is a flowchart illustrating a method for detecting ions of heavy metallic element using ion recognizing molecule or ionophores with preferential binding to specific ion.
• FIG. 3 is a flowchart illustrating a method for allowing passage of current across channel through at least one channel on substrate in communication with at least two electrodes.
• FIG. 4 illustrates a plot of conductance versus logarithmic of lead concentration.
• the present invention provides an apparatus and a method for detecting ions of heavy metallic element comprising at least one polymeric binder to secure and immobilize lead (II) ion recognizing molecule onto ion sensing channels.
• II lead
• this specification will describe the present invention according to the preferred embodiments. It is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned without departing from the scope of the appended claims.
• FIG. 1 illustrates lead (II) sensor without using reference electrode.
• Miniaturized and self-powered sensor which is used to monitor industrial discharge and quality of water in the rivers, especially those used to supply fresh water for daily use is illustrated in FIG. 1.
• the present invention proposes selective lead (II) ion sensor based on ionophore without using reference electrode.
• an apparatus (100) for detecting ions of heavy metallic element comprising at least one polymeric binder (102) to secure and immobilize lead (II) ion recognizing molecule onto ion sensing channels; conductive filler particles (104) to reduce impedance across channel and adjust baseline of electrical conductivity; ion recognizing molecule or ionophores (106) with preferential binding to bind lead (II) ion selectively in the presence of interfering ions; and at least one channel on a substrate (108) in communication with at least two electrodes (110) to allow passage of current across channel through at least one channel on substrate (108) in communication with at least two electrodes (110).
• the lead (II) ion recognizing molecule or ionophores (106) is immobilized onto ion sensing channels sandwiched by conductive pads for electrical communication.
• the lead ionophore (106) is secured on the channel with low impedance polymeric matrix such as ethyl cellulose.
• Sufficient amount of conductive particles (104) such as carbon nanotubes are added to adjust the baseline conductivity of the channel.
• the lead (II) sensor (100) of the present invention is field deployed in a miniaturized sensor system that automatically analyzes the trace-level of the toxicity of lead (II) ions in rivers and industrial discharge in order to transmit the data via wireless means.
• the lead (II) sensor (100) comprises multiple narrow and elongated channels filled with lead recognizing molecule (106), immobilized by low impedance polymeric binder (102).
• the binder preferably contains polar group and can be cured with mild heating. It is also desired that the organic binder contains cross-linkable moiety that cross links upon heat treatment.
• the at least one polymeric binder (102) may comprise of at least one combination of cellulose acetate, ethyl cellulose, cellulose, (methyl methacrylate-glycidyl methacrylate) copolymer, (methyl methacrylate-glycidyl methacrylate-tetrahydrofurfuryl acrylate) copolymer.
• the sensing channel is sandwiched between at least two electrodes to measure the current and conductance across the channel.
• the said electrodes are screen printed silver on printed circuit board (PCB) substrate.
• the at least one channel of the sensor system may comprise of 0.5 to 8 % lead ionophore, 80 to 90% polymeric binder and 10 to 20% conductive filler, all by weight.
• the baseline conductance of the channel is adjusted using conductive particles (104) which may comprise of at least one combination of platinum, silver, gold, carbon nanotubes, graphite, pyrolitic carbon, glassy carbon.
• the substrate (108) in communication with at least two electrodes (110) may comprise of at least one of the following materials; alumina, glass, paper, silicon dioxide, silicon nitride.
• the detection limit and linear range of the lead sensor (100) can be optimized by changing the composition of the main components; lead ionophore (106), low impedance binder (102) and conductive filler (104).
• the presence of trace amount of lead ion can be detected from the change in the conductivity across the channel while the presence of lead ions linearly increases the conductivity of the sensing channel.
• FIG. 2 is a flowchart illustrating a method for detecting ions of heavy metallic element using ion recognizing molecule or ionophores with preferential binding to specific ion
• FIG. 3 is a flowchart illustrating a method for allowing passage of current across channel through at least one channel on substrate in communication with at least two electrodes.
• a method (200) for detecting ions of heavy metallic element using ion recognizing molecule or ionophores with preferential binding to specific ion comprising steps of securing and immobilizing lead (II) ion recognizing molecule onto ion sensing channels (202).
• Lead (II) ion recognizing molecule is secured and immobilized onto ion sensing channels (202) wherein securing and immobilizing lead (II) ion recognizing molecule onto ion sensing channels (202) further comprises carrying selected ions across polymeric sensing matrix. Thereafter, impedance across channel is reduced and baseline of electrical conductivity is adjusted (204) by adding conductive particles to reduce impedance across channel beyond limit of organic binder. Lead (II) ion is selectively bound in the presence of interfering ions (206). Subsequently, passage of current across channel is allowed through at least one channel on substrate in communication with at least two electrodes (208).
• the passage of current across channel is allowed through at least one channel on substrate in communication with at least two electrodes (208) further comprises measuring differential conductance and analyte concentration to determine response and sensitivity of sensor (302); and plotting conductance against analyte concentration to determine conductance of channel (304).
• Example 1 Preparation and Characterization of Selective Lead (II) Sensor
• Lead ionophore (Fluka, 2mg), 2 mg of carbon nanotubes and 50mg of cellulose acetate are added into a 5-mL transparent glass vial with air-tight cap.
• Tetrahydrofuran (THF, 1 mL) is added into the vial and the mixture is sonicated for 5 minutes at 35 °C to achieve homogenous cocktail containing 4 weight percent (compared to cellulose acetate) of lead ionophore and 5% solution of cellulose acetate in THF.
• Interdigitated multiple channels are defined by screen printing comb structures of silver electrodes. The distance across the channel is 1mm and the length of the channel is 3mm. The entire surface of the device is covered with screen printed solder mask or epoxy insulating materials, exposing only the contact windows to silver electrodes. The screen printed layers are oven cured at 120 °C under blanket of nitrogen gas for 30 minutes. The cocktail composition is dispensed to cover the channel windows and dried under continuous flow nitrogen gas for 30 minutes and further air dried overnight.
• One of the electrodes is grounded while the other is applied with DC voltage from 0.5V to 1.5V with 0.1V increment. The current across the channel is measured at each applied voltage.
• the approach of the present invention lies in the detection of the trace amount of lead which is detected by the change of conductivity of the sensing channel wherein the selectivity towards lead ion is achieved by ionophore.

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• Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
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Cited By (7)

Citations (1)

• 2012
  • 2012-03-21 MY MYPI2012001289A patent/MY155093A/en unknown
• 2013
  • 2013-03-18 WO PCT/MY2013/000053 patent/WO2013141692A1/fr not_active Ceased

Patent Citations (1)

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