Ph meter

a technology of ph meter and meter, which is applied in the field of improved analyte sensors, can solve the problems of difficult, insufficient sample contact for semi-solid samples of small volume, and many challenges of glass probes designed for small sample volumes, and achieve the effect of facilitating small gaps and not reducing measurement sensitivity

Inactive Publication Date: 2015-12-03
PARKER HANNIFIN CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0012]In some implementations, the present invention provides sensors with substantially flat sensing surfaces on which all sensing elements are located co-planar to one another. These configurations allow even small volumes of sample to contact all sensing elements, for example in the form of a liquid film captured between the sensing surface and another solid surface. Optionally, the sensing elements may be located on opposite surfaces capturing the liquid. The sample is held by capillary action within the gap formed by the sensor without the use of a sample container. In this way the sample size is no longer dependent on the size of the sensor, but rather by the dimension of the gap formed by the sensor and a complementary surface. As an example, by adjusting the size of the gap formed by a 12-mm diameter flat sensor and another 12-mm diameter cylinder, a uniform liquid film can be formed with a volume of 10 microliters or less. Second, the sensitivity of measurement is not reduced as the sample volume decreases, because sensitivity is primarily a function of the surface area of the sensor and not of the sample volume. Indeed, sensor surface areas substantially larger than that possible with conventional glass probes can be made to allow detection of low analyte concentrations. Thus, some implementations of the current invention provide systems that enable precise containment of small sample volumes, as well as sensors with planar geometries that facilitate formation of small gaps with a complementary solid surface, including arrangements where the sensing elements are located on one or both sides of that defined space.

Problems solved by technology

Very few specialized glass probes containing a working electrode (the “sensor”), reference electrode, and counter electrodes are available that are advertised as capable of measuring pH in sample volumes as low as 0.5 microliter, and those are very expensive (e.g. Thermo Scientific Orion 9810 BN).
However, glass probes designed for small sample volumes present many challenges.
One challenge is positioning of the probe in the sample.
The bulbous shape of glass probes makes this challenge especially difficult.
Similarly, semi-solid samples, such as from a tissue biopsy, may require larger volumes, relative to that for liquid samples, when using glass electrodes, as the shape of the probe again may lead to inadequate sample contact for semi-solid samples of small volume.
Another challenge is the potential for contamination of samples due to transfer of salts or other materials (“mass”) from the electrodes in the probe into the sample.
Another challenge is sample evaporation, as evaporation is relatively greater in low volume samples, and evaporative effects may be difficult to monitor.
Loss of sample volume can lead to erroneous results.
As pH measurement using a glass electrode requires that a potentiometric signal reach steady state (as may be defined by algorithms for a given system), decreasing measurement time is inherently a limited approach.
Glass probes are relatively expensive to manufacture, however, and, for repeat use, they must be rinsed between samples to reduce the chances for cross contamination, further impeding high sample throughput in pH measurement.
Fouling, a source of drift and error, is also particularly problematic with glass probes, because samples containing protein, sugar, or other constituents that interact with the glass can foul the probe.
These operations increase the risk of damage, which only increases in the small confines necessitated by small volume samples.
A further limitation arises from the liquid junction of the reference electrode.
However, in very small samples, passage of internal reference solution into the analyte changes the composition of the analyte and can negatively affect the measurement.
This liquid junction gives rise to possible contamination of the internal KCl solution, which would change the electrode potential, resulting in drift of the measurement.
Other disadvantages include the propensity to leakage of the internal electrolyte, and clogging due to drying or precipitation inside the liquid junction.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0121]A RAM suitable for use in printing inks and coating formulations for sensor fabrication was synthesized according to the equation provided in Formula I, as follows:

[0122]1,5-dichloroanthraquinone (20 gm, 0.072 moles) was stirred in ethylene glycol (300 mL). To this mixture was added potassium hydroxide pellets (11.8 gm, 85%, 0.179 moles). This reaction was stirred at 120° C. and after approximately 2 hours a dark red solution had formed. Heating was continued for an additional 16 hours. After cooling, the reaction mixture was added to water (800 mL) and this was left at room temperature overnight. The solid which had separated was isolated by filtration and dried. The dried solid was stirred overnight in diethyl ether (500 mL) which dissolved most of the un-reacted starting quinone. The insoluble material was isolated by filtration and dried to give 11.1 gm of crude product. The crude product was stirred in a mixture of methanol and methylene chloride (50 mL of 10% methanol in...

example 2

[0123]A RAM suitable for use in printing inks and coating formulations for sensor fabrication was synthesized according to the equation provided in Formula II, as follows:

[0124]A mixture of 1-chloroanthraquinone (17.5 gm, 0.072 moles) and powdered potassium hydroxide (5.9 gm of 85%, 0.09 moles) was stirred in 1,3-propanediol (200 mL). This mixture was stirred at 120° C. for 24 hours. After cooling, the brown solution was poured into water (500 mL) and after settling overnight, the solids were isolated by filtration. The filter cake was washed with water and air dried. The dried solid was dissolved in methylene chloride (600 mL) and filtered free of insoluble material. The filtrates were dried over magnesium sulfate, filtered and then evaporated under reduced pressure to give a brown solid. A 5 gm sample of the crude, brown solid was dissolved in methylene chloride (20 mL) and this solution was placed on top of a silica column. Un-reacted 1-chloroanthraquinone was eluted using methyl...

example 3

[0125]A RAM suitable for use in printing inks and coating formulations for sensor fabrication was synthesized according to the equation provided in Formula III, as follows:

[0126]A mixture of 1-chloroanthraquinone (15 gm, 0.062 moles) and 2-(2-aminoethoxyl)ethanol (105 gm 1.0 moles) was stirred at 90° C. for 16 hours. The hot solution was poured into water (500 mL) and the solids were isolated by filtration. The filter cake was washed with water and air dried. The dried solid was recrystallized from 2-propanol (300 mL) to provide 14.0 gm of product as a red solid.

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Abstract

Voltammetric sensors prepared from composite materials and optionally using microfabrication techniques enable detection of analyte in sample volumes under ten microliters.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention provides improved analyte sensors that enable precise measurement of analyte concentrations, including but not limited to hydronium ion concentration or pH. The invention relates generally to the field of analytical chemistry and specifically to pH measurement technology.[0003]2. Description of Related Disclosures[0004]Measurement of analyte concentration, such as pH, in samples is constrained by available sample volume. Most commercially available pH electrodes require at least milliliter volume samples. Very few specialized glass probes containing a working electrode (the “sensor”), reference electrode, and counter electrodes are available that are advertised as capable of measuring pH in sample volumes as low as 0.5 microliter, and those are very expensive (e.g. Thermo Scientific Orion 9810 BN). However, glass probes designed for small sample volumes present many challenges.[0005]One challenge i...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01N27/416G01N27/30
CPCG01N27/301G01N27/4167G01N27/36G01N27/4165G01N27/302
Inventor LEE, ERICROTH, STEVEVU, THANG HUY
Owner PARKER HANNIFIN CORP
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