WO1994015207A1 - Improvements in or relating to electrochemical reactions - Google Patents
Improvements in or relating to electrochemical reactions Download PDFInfo
- Publication number
- WO1994015207A1 WO1994015207A1 PCT/GB1993/002615 GB9302615W WO9415207A1 WO 1994015207 A1 WO1994015207 A1 WO 1994015207A1 GB 9302615 W GB9302615 W GB 9302615W WO 9415207 A1 WO9415207 A1 WO 9415207A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- reagent
- electrode
- reaction according
- solution
- reaction
- Prior art date
Links
- 238000003487 electrochemical reaction Methods 0.000 title claims abstract description 12
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 65
- 238000012544 monitoring process Methods 0.000 claims abstract description 14
- 150000003839 salts Chemical class 0.000 claims abstract description 14
- 238000004519 manufacturing process Methods 0.000 claims abstract description 9
- 230000004044 response Effects 0.000 claims abstract description 9
- 239000000243 solution Substances 0.000 claims description 35
- 238000006243 chemical reaction Methods 0.000 claims description 32
- -1 hydrogen ions Chemical class 0.000 claims description 17
- 230000001603 reducing effect Effects 0.000 claims description 11
- 239000001257 hydrogen Substances 0.000 claims description 10
- 229910052739 hydrogen Inorganic materials 0.000 claims description 10
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 10
- 239000007789 gas Substances 0.000 claims description 8
- 235000000346 sugar Nutrition 0.000 claims description 6
- 235000010344 sodium nitrate Nutrition 0.000 claims description 5
- 239000004317 sodium nitrate Substances 0.000 claims description 5
- 238000004448 titration Methods 0.000 claims description 5
- XTEGARKTQYYJKE-UHFFFAOYSA-M Chlorate Chemical compound [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 claims description 4
- 239000011148 porous material Substances 0.000 claims description 4
- 239000007864 aqueous solution Substances 0.000 claims description 3
- 238000002848 electrochemical method Methods 0.000 claims description 3
- 239000003014 ion exchange membrane Substances 0.000 claims description 3
- 150000002500 ions Chemical class 0.000 claims description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 2
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 claims description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 2
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052794 bromium Inorganic materials 0.000 claims description 2
- 239000000460 chlorine Substances 0.000 claims description 2
- 229910052801 chlorine Inorganic materials 0.000 claims description 2
- 229910052744 lithium Inorganic materials 0.000 claims description 2
- 239000012528 membrane Substances 0.000 claims description 2
- VLTRZXGMWDSKGL-UHFFFAOYSA-M perchlorate Inorganic materials [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 claims description 2
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 claims description 2
- 229910052700 potassium Inorganic materials 0.000 claims description 2
- 239000011591 potassium Substances 0.000 claims description 2
- VKJKEPKFPUWCAS-UHFFFAOYSA-M potassium chlorate Chemical compound [K+].[O-]Cl(=O)=O VKJKEPKFPUWCAS-UHFFFAOYSA-M 0.000 claims description 2
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 claims description 2
- 229910052939 potassium sulfate Inorganic materials 0.000 claims description 2
- 239000001120 potassium sulphate Substances 0.000 claims description 2
- 235000011151 potassium sulphates Nutrition 0.000 claims description 2
- 229910052708 sodium Inorganic materials 0.000 claims description 2
- 239000011734 sodium Substances 0.000 claims description 2
- 229910021653 sulphate ion Inorganic materials 0.000 claims description 2
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 claims 1
- 239000011630 iodine Substances 0.000 claims 1
- 229910052740 iodine Inorganic materials 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 15
- 238000009792 diffusion process Methods 0.000 abstract description 5
- 238000011065 in-situ storage Methods 0.000 abstract description 3
- RFSUNEUAIZKAJO-ARQDHWQXSA-N Fructose Chemical compound OC[C@H]1O[C@](O)(CO)[C@@H](O)[C@@H]1O RFSUNEUAIZKAJO-ARQDHWQXSA-N 0.000 description 12
- 229930091371 Fructose Natural products 0.000 description 12
- 239000005715 Fructose Substances 0.000 description 12
- 239000003513 alkali Substances 0.000 description 11
- 239000008364 bulk solution Substances 0.000 description 8
- 238000005259 measurement Methods 0.000 description 7
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 239000010931 gold Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229910052709 silver Inorganic materials 0.000 description 5
- 239000004332 silver Substances 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 4
- 229910021607 Silver chloride Inorganic materials 0.000 description 4
- 238000013459 approach Methods 0.000 description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 4
- 229910052737 gold Inorganic materials 0.000 description 4
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 4
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 3
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- 239000012491 analyte Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 229910001882 dioxygen Inorganic materials 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000001103 potassium chloride Substances 0.000 description 3
- 235000011164 potassium chloride Nutrition 0.000 description 3
- 238000007650 screen-printing Methods 0.000 description 3
- 241000894007 species Species 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 238000004401 flow injection analysis Methods 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- 229910052763 palladium Inorganic materials 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 150000008163 sugars Chemical class 0.000 description 2
- 239000012085 test solution Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 125000000129 anionic group Chemical group 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000003869 coulometry Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 235000013399 edible fruits Nutrition 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 235000012055 fruits and vegetables Nutrition 0.000 description 1
- 239000000499 gel Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- PNDPGZBMCMUPRI-UHFFFAOYSA-N iodine Chemical compound II PNDPGZBMCMUPRI-UHFFFAOYSA-N 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 239000011133 lead Substances 0.000 description 1
- 238000012417 linear regression Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 244000005706 microflora Species 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000020477 pH reduction Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000128 polypyrrole Polymers 0.000 description 1
- 159000000001 potassium salts Chemical class 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 229910021655 trace metal ion Inorganic materials 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 235000013311 vegetables Nutrition 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
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
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/416—Systems
- G01N27/42—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte
- G01N27/44—Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte using electrolysis to generate a reagent, e.g. for titration
Definitions
- This invention concerns electrochemical reactions.
- the present invention provides an electrochemical reaction, wherein a controlled amount of a first reagent is generated electrochemically at an electrode in electrical contact with a solution of an electrochemically inert salt, comprising applying a suitable electrical potential to the electrode for a suitable time to generate a controlled amount of the first reagent by electrochemical reaction between the electrode and a species in solution producing a localised thin layer environment comprising the first reagent in the vicinity of the electrode; and monitoring the amount or presence of the first reagent or a further species produced in solution in response to production of the first reagent.
- thin layer means having a thickness less than 1mm, preferably in the range 0.1 to 0.2mm.
- the method of the invention thus involves generating the first reagent in situ at an electrode. Diffusion of the reagent in solution surrounding the electrode will result in creation of a localised environment of the reagent in the vicinity of the electrode, with the amount of reagent depending on the generating current and the length of time for which it is applied, and so being readily and easily controllable.
- Reagent generated by this approach can be used in two main ways:
- the first reagent may comprise hydrogen ions or hydroxyl ions. These are readily produced by application of an electrical potential to water, eg an aqueous solution of a reactant. Depending on the polarity of charge at an electrode, water is broken down according to the following equations:
- reagents such as chlorine, bromine, and iodine
- suitable salt solutions eg KC1, KBr, KI.
- the first reagent may be used to generate a further reagent to create a desired environment or participate in a desired reaction. For example, by covering the electrode with an ion-exchange membrane containing an ion of interest, reagent such as EDTA can be expelled from the membrane in response to contact with hydroxyl ions generated at the electrode.
- reagent such as EDTA
- the porous material can be porous paper, such as blotting paper, porous ceramic material, porous ion exchange material, porous dielectric material, porous polymer etc.
- Certain of these materials can conveniently be applied by screen printing over the electrode, or by in situ polymerisation, eg initiated by exposure to UV light.
- hydrogen gas its concentration in solution can be reduced by employing palladium electrodes, as this material absorbs hydrogen.
- oxygen gas its evolution can be prevented by employing a sacrificial metal anode, for example of silver, lead or zinc. Other approaches may also be possible.
- the invention finds particular application in measurements on thin layers of reagent, constrained within impervious barriers, eg capillary fill devices (CFDs) or narrow bore tubes with diameters of thin layer dimensions but unspecified length.
- CFDs capillary fill devices
- a typical CFD comprises two plates separated by a gap sufficiently small that liquid can be drawn into it by capillary action.
- the gap is generally less than 1mm, preferably in the range 0.1 to 0.2mm.
- the internal faces of the plates carry electrodes, eg deposited by screen printing, for making electrochemcial measurements.
- the plate spacing or tube bore will constrain the extent of the localised environment in the vicinity of the electrode in one dimension (generally perpendicular to the electrode surface).
- the extent of the localised environment in other dimensions (generally parallel to the electrode surface, ie in a lateral direction) will depend on the extent of the electrode and the rate of lateral diffusion of the first reagent in solution. It is found in practice in a CFD that lateral diffusion is generally slow, typically being of the order of 1mm in 120 seconds. Lateral diffusion can also be controlled if required by use of a guard electrode, as described in the specification of British Patent Application No. 9325189.0.
- the thin layer environment can also be defined by interstices or recesses, eg pores, wells or channel of thin layer dimensions, in solid matrices eg of paper, gels, (water soluble or unsoluble), polymers, ion exchange membranes etc.
- Such thin layer environments may be in contact with bulk solution, eg with one or more wells formed in suitable matrix material located in a bulk solution container, thus enabling effective generation of one or more localised thin layer environments in communication with bulk solution, so that diagnostic reactions etc. can be performed within the thin layer environment.
- the localised thin layer environment may be used in isolation, eg in the case of CFDs and narrow bore tubes containing sample.
- the thin layer environment may be employed in conjunction with bulk solution, eg with a tube or test strip defining a thin layer environment dipping into bulk solution, or as with recesses in a bulk solution container as discussed above.
- the electrode should be inert with respect to reactants involved in reactions taking place, so no undesired side reactions occur.
- Suitable electrode materials include gold, platinum, palladium, silver, carbon, carbon/silver, porous conducting ceramic materials, electrically conducting polymeric substances, eg polypyrrole.
- the electrochemically inert salt provides inert ions which function as charge carriers during the process.
- Suitable salts include salts of sodium, potassium, lithium, ammonium etc, with potassium salts generally being favoured currently.
- the anionic component may be, for example, nitrate, sulphate, chlorate, perchlorate, fluoroborate etc. Potassium sulphate, potassium chlorate and sodium nitrate are currently favoured salts.
- the salt will typically be in aqueous solution and possess a sufficiently high oxidation/reduction potential so as not to take part in the electrochemical process.
- Suitable electrical potentials and times will depend on the conditions and reactions involved, and can be readily determined in any given case. As an example, for a measurement in a CFD application of a current of 3mA for about 60 seconds or less might be suitable.
- the first reagent it may be appropriate to monitor the first reagent, a further species produced in solution in response to production of the first reagent, or both of these.
- the first reagent may particpate in an electrochemical reaction, so by monitoring depletion of the first reagent an indication is obtained of the extent of reaction.
- Production of the first reagent may also be exploited in flow measurement, by generating a pulse of first reagent at known time in a flowing solution and monitoring at a downstream detector the time internal between generation of the pulse and arrival of the pulse at the detector, thus providing a measure of the rate of flow of the solution.
- monitoring takes place at a location remote from the electrode where the first reagent is produced.
- Monitoring may be effected directly or indirectly, and may be qualitative or quantitive.
- a variety of different monitoring techniques may be employed, involving monitoring of a range of properties of the solution. For example the appearance, eg colour or cloudiness, of the solution may be monitored using colourimetric, spectrophotometric or turbidometric techniques. Electrochemical monitoring is a particularly convenient approach, and potentiometric or coulometric (eg amperometric) techniques can be used as appropriate, with appropriate techniques being selected as a matter of design choice.
- An internal electrochemical reference system can readily be provided in known manner, eg in a CFD, by a suitable reference electrode such as a silver/silver chloride electrode.
- the invention may be embodied in several forms, including a CFD and in devices designed to be used with bulk solution.
- the technique may also be useful for the local generation of acid or alkali conditions in bulk solution containing some analyte requiring pH manipulation.
- the advantage of this embodiment over existing techniques is that acidification/alkalinisation of the entire solution is not necessary, resulting in significant cost advantages.
- the invention may also be exploited for the measurement of laminar flow rates inside tubes.
- the tube need not necessarily be of thin layer diameter: in wider bore tubes laminar flow may result in a thin layer of flowing medium (constituting a thin layer environment) being present adjacent the tube side wall.
- a pulse of reagent eg alkali/acid may be generated at some point upstream of a detector, and the time between generation and detection may be used to calculate flow rates.
- this technique may also be used to reduce the bio-fouling of tubes, by generating hydrogen ions to decomplex any trace metal ions in solution. This technique has particular applications in the sewage and waste-water treatment industries. Provided adequate mixing of the solution at some point down-stream of the pulse occurs, the microflora in the reactors should not be affected as there is no net pH change.
- the invention may also have a particular application for the performance of pH-titrations, especially in a flow- injection analysis system (FIA).
- FAA flow- injection analysis system
- the concentration of alkali or acid may be ascertained. For example by employing stepped pulses of charge and intermittently or continuously measuring the potential, the concentration of analyte may be determined.
- An auto- titrator employing such a system would have advantages over existing system in terms of a reduction of reagent costs, and in the volume of sample required.
- Figure 1 is a schematic cross-sectional view of a CFD in accordance with the invention
- Figure 2 is a plan view of the CFD of Figure 1 on a reduced scale
- Figure 3 is a graph of potential difference versus time obtained using the CFD of Figures 1 and 2, with different concentrations of fructose in solution;
- Figure 4 is an enlarged scale version of the end portions of the curves of Figure 3;
- Figure 5 is a graph of final potential versus log fructose concentration obtained from graphs such as Figure 4.
- Figure 6 is a schematic cross-sectional view of a modification of the embodiment of Figures 1 and 2.
- FIGS 1 and 2 illustrate schematically a CFD in accordance with the invention and its use in generating localised acid and alkali environments, eg for use in determining the concentration of reducing sugar in a test solution.
- the CFD is generally of conventional construction, eg as described in EP 0170375 A.
- the CFD comprises two spaced apart plates 10 and 12, eg of glass, ceramic or plastics material, separated by a gap of about 0.1mm.
- the lower plate 10 carries 3 electrodes: an acid generator gold electrode 14, an alkali generator gold electrode 16, and a sliver/silver chloride reference electrode 18.
- the electrodes are deposited using conventional screen printing techniques.
- Conductors 20 extending through a dielectric layer 22 (shown in Figure 2 by cross-hatching) connect the electrodes to respective contact or terminal pads 24.
- a porous layer 26 (for clarity not shown in Figure 2) is deposited on top of the electrodes to prevent agitation or mixing of solution in the CFD on production of gas bubbles at the electrodes.
- a layer of porous ceramic or ion exchange material will be screen printed over the electrodes.
- the apparatus finds application, for example, in determining the concentration of reducing sugar in a test solution, using the technique as described in the specification of British Patent Application No. 9325189.0.
- the alkali zone 30 consititutes a suitable environment in which fructose (or other reducing sugars) can have a reducing effect, reducing available reducible reagents.
- fructose or other reducing sugars
- oxygen present in the system was used as the electron acceptor for the oxidation of fructose.
- Electrode 18 was thus located within the alkali zone 30.
- Figure 5 is a plot of further results obtained in generally similar manner, demonstrating a clear (logarithmic) correlation between fructose concentration and final potential.
- the CFD of Figures 1 and 2 can alternatively be used in pH titrations.
- the potential between electrodes 14 and 16 is applied in short pulses, with the resulting potential of electrode 16 (and hence change in pH in the vicinity of that electrode) being measured by use of reference electrode 18 between each pulse.
- a characteristic sigmoidal curve is obtained, in which the point of inflection indicates the point of neutrality.
- suitable computer control means desirably programmed to vary the size of applied pulses depending on the circumstances, reducing the pulse size as the end point of neutrality is approached for enhanced accuracy.
- charge can be applied continuously and the effect monitored continuously, rather than in pulsed manner, by use of separate, independent charging and monitoring circuits.
- one of the generator electrodes say alkali generator 16 carries a pair of sensor electrodes 32, 34 on its upper surface, separated from that surface by respective dielectric layers 36.
- the sensor pair conveniently comprises a gold electrode 32 and a silver/silver chloride electrode 34.
- Porous layer 26 covers all the electrodes.
- the method of the invention may, for example, be used to determine the ripeness of fruit and vegetables. This would involve measuring the fructose (and other reducing sugars) content of liquor expressed from a fruit or vegetable sample, eg as described above.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE69325108T DE69325108T2 (en) | 1992-12-23 | 1993-12-21 | IMPROVEMENTS IN ELECTROCHEMICAL REACTIONS |
EP94902925A EP0679253B1 (en) | 1992-12-23 | 1993-12-21 | Improvements in or relating to electrochemical reactions |
US08/464,715 US5840171A (en) | 1992-12-23 | 1993-12-21 | Electrochemical reactions |
JP51494194A JP3499872B2 (en) | 1992-12-23 | 1993-12-21 | Improvements in or relating to electrochemical reactions |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB929226840A GB9226840D0 (en) | 1992-12-23 | 1992-12-23 | Improvements in or relating to electrochemical reactions |
GB9226840.8 | 1992-12-23 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1994015207A1 true WO1994015207A1 (en) | 1994-07-07 |
Family
ID=10727126
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1993/002615 WO1994015207A1 (en) | 1992-12-23 | 1993-12-21 | Improvements in or relating to electrochemical reactions |
Country Status (8)
Country | Link |
---|---|
US (2) | US5840171A (en) |
EP (1) | EP0679253B1 (en) |
JP (1) | JP3499872B2 (en) |
AT (1) | ATE180568T1 (en) |
DE (1) | DE69325108T2 (en) |
ES (1) | ES2131667T3 (en) |
GB (1) | GB9226840D0 (en) |
WO (1) | WO1994015207A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0973028A2 (en) * | 1998-07-14 | 2000-01-19 | Oxley Developments Company Limited | Electrode array |
Families Citing this family (57)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB9226840D0 (en) * | 1992-12-23 | 1993-02-17 | Unilever Plc | Improvements in or relating to electrochemical reactions |
US6036924A (en) | 1997-12-04 | 2000-03-14 | Hewlett-Packard Company | Cassette of lancet cartridges for sampling blood |
US6391005B1 (en) | 1998-03-30 | 2002-05-21 | Agilent Technologies, Inc. | Apparatus and method for penetration with shaft having a sensor for sensing penetration depth |
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Also Published As
Publication number | Publication date |
---|---|
ATE180568T1 (en) | 1999-06-15 |
GB9226840D0 (en) | 1993-02-17 |
JP3499872B2 (en) | 2004-02-23 |
EP0679253B1 (en) | 1999-05-26 |
JPH08507369A (en) | 1996-08-06 |
DE69325108D1 (en) | 1999-07-01 |
ES2131667T3 (en) | 1999-08-01 |
US5840171A (en) | 1998-11-24 |
EP0679253A1 (en) | 1995-11-02 |
DE69325108T2 (en) | 1999-12-23 |
US6039861A (en) | 2000-03-21 |
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