WO2015198151A2

WO2015198151A2 - Automatic colorimetric titration device with noninvasive probe

Info

Publication number: WO2015198151A2
Application number: PCT/IB2015/001656
Authority: WO
Inventors: Igor A. SHALALOV
Original assignee: Shalalov Igor A
Priority date: 2014-06-22
Filing date: 2015-06-22
Publication date: 2015-12-30
Also published as: WO2015198151A3

Abstract

A volumetric titration device is provided having a diode for emitting light in the range from 350nm to 1000nm. The light directed through a titration is modulated at a frequency higher than can be detected by a human eye (for example, more than 40Hz) to avoid the interference resulting from background light noise. A photodetector placed under a titration vessel measures light intensity in different light ranges.

Description

AUTOMATIC COLORIMETRIC TITRATION DEVICE

WITH NONINVASIVE PROBE

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to chemical titration systems and, more particularly, to an automated colorimetric titration system and methods with a

noninvasive probe.

2. Description of the Related Art

Titration is a well-known analytical technique. It has been widely used, for many years. This method of analysis is very popular, and that is due to the

following reasons:

1. Good results can be achieved by using the minimum of equipment, e.g. glass or plastic burettes; and

2. Concentration of many different substances can be determined with this method.

The regular titration procedure is based on the addition of titrant of known concentration, which reacts with the sample of unknown concentration. Reaching the endpoint or the equivalence point of titration causes a definite change in color, pH, ion concentration,

conductivity, temperature, or in other physical parameters of the solution.

These changes can be detected mainly by a human eye, a photo probe, a potentiometric electrode, or a

conductivity electrode.

The most popular ways of adding titrant to the solution are volumetric or colorimetric .

The invention below deals with volumetric addition of reagent (titrant ) with colorimetric or potentiometric endpoint or equivalence point determination.

Colorimetric titration with regular glass or plastic burettes has several drawbacks:

1. A skilled analyst is required to avoid mistakes in determination of color corresponding to the endpoint titration; and

2. Titrations with adsorption changes out of the visible range of light spectrum cannot be carried out.

In order to overcome some of these drawbacks, potentiometric titration was invented. It is possible to make automated titrations using this method. Nevertheless this method also has several limitation:

1. Not many colorimetric titration methods can be transferred to potentiometric titration methods; and

2. If during a titration procedure a sedimentation occurs, the method does not work well due to the reason that the potentiometric probe has to be placed in a reaction vessel.

Many attempts have been made to automate non^¬ invasive colorimetric titration. It was found

complicated because of the following reasons:

1. Sunlight, shadows cast by a body passing by, incandescent sources, etc., make very complicated the measurement of change in absorption;

2. In order to detect color change, absorption has to be measured on several wavelengths simultaneously; and

3. During titration the liquid in the reaction vessel is stirred. It creates a vortex, which makes correct determination of absorption via any noninvasive way difficult.

A search of the prior art for a solution to the problem did not disclose any patents that read directly on the claims of the instant invention. However, the following reference were identified as being the most successful attempts relating to the automation of non- invasive colorimetric titration.

International publication WO1995003537, published in the name of Biotechtronix, Inc, describes a colorimetric titration method and apparatus in which the titrating apparatus comprises a radiant energy means and a means for modulating an amplitude of an intensity of the radiant energy. An adjacent solution within a sample beaker having a color indicator dissolved therein

partially absorbs the radiant energy. A radiant energy detector produces a transmitted signal. Filtering means filters the transmitted signal and produces a filtered transmitted energy signal representative of only the amount of radiant energy transmitted through the solution from the radiant energy source, free of other sources of radiant energy. The colorimetric titrator also includes means for constructing a titration curve, means for computing the first derivative of the titration curve, means for computing the second derivative of the

titration curve, control means for controlling titrant addition means in response to the first derivative of the titration curve, and means for calling the endpoint of the titration by using the second derivative.

International publication WO2008012145A1, published in the name of Foss Analytical AB, describes a system and method for colorimetric titration measurements comprising a container and a mixing device which is arranged to extend along a substantial portion of a longitudinal axis of the container. An analysis arrangement having a housing in the form of a collar is adapted to fit around and at least partially enclose a section of said

container extending in a plane substantially

perpendicular to the longitudinal axis of the container and not intersected by the mixing device in the

container. The collar houses at least one electromagnetic radiation source, arranged to emit electromagnetic radiation towards said container; and at least one electromagnetic radiation detector, arranged to detect electromagnetic radiation, emitted from the at least one electromagnetic radiation source through the container.

And, international publication W02009017461, published in the name of Ramasamy, describes a titration apparatus having a sensor to detect the end-point of a titration. The sensor is a light sensor monitoring a change of colour in the analysis sample and may be calibrated to account for turbidity or colouration in the analysis sample. The titration apparatus therefore provides the possibility of overcoming interference from turbidity or colouration in the analysis sample to the end-point detection. This provides the advantage of relieving the need for extensive sample preparation before titration, allowing titration to be performed in the field.

In all of these references, light modulation was applied in order to overcome interference from background noise. Several light diodes with different wavelengths were used to detect color changes. In order to prevent vortex creation in the invention W02008012145A1, a special reaction vessel was used. This vessel is not convenient for routine titration.

In the inventions found in W01995003537A1 and

W02009017461A1, to measure the absorbance correctly in the presence of such a vortex, light emitting diodes and/or photo diode were placed in the radiant direction. These constructions have also several limitations: (a) due to radiant positions, not a large range of the vessels can be used; (b) it is not convenient to place titration vessel in the correct position; and © the height of the vortex must be controlled and has to be out of light-measuring paths.

Consequently, a need exists for an apparatus and method for a simple, reliable and repeatable method for automating colorimetric titration, and an apparatus for performing the same that overcomes these and other drawbacks of the existing art.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an automatic colorimetric titration system.

It is a feature of the present invention to provide such a system having a noninvasive probe and titration methods that can be realized on the basis of this system.

Briefly described according to the present

invention, a volumetric titration device is provided with a diode adapted to emitting light in a selected range and modulated at a frequency higher than can be detected by a human eye (such as, for example, more than 40Hz) . A probe with the diode is placed under a titration vessel and light emitted down through the vessel to the magnetic stirrer. Several photo diodes are then used to measure light intensity in different light ranges. The intensity of this light can then measured on several wavelengths and at the beginning of and during the titration. The channel with the greatest change in intensity is then normalized relative to the channel with the smallest change .

It is an advantage of the present invention to allow for compensation for changes in diode intensity as compared to background light noise.

It is another advantage of the present invention to greatly reduce the affect that the presence of a vortex has in measuring of the normalized intensity. It is yet another advantage of the present invention to provide an instrument that can detect very slight color change which otherwise cannot be detected by any human eye.

Further, the presence of a noninvasive probe in the present invention gives several advantages over, for example, a potentiometric titrator, including: non^¬ interference with composition of the titration solution; easier automation due to absence of any necessary

cleaning of the probe; extended life of the probe as compared to existing methods.

Further still, the present invention accommodates many different titrations, including the ability to develop totally new ones.

Further aspects, objects, features and advantages of the invention will become apparent in the course of the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and features of the present invention will become better understood with reference to the following more detailed description and claims taken in conjunction with the accompanying drawings, in which like elements are identified with like symbols, and in which: FIG. 1 is an photograph of an automated colorimetric titration system enabling the preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example systems, methods, processes, and so on are now described. In the following description, for purposes of explanation, numerous specific details are set forth in order to facilitate thoroughly understanding the methods, systems, processes, and so on. It may be

evident, however, that the methods, systems and so on can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to simplify description.

The best mode for carrying out the invention is presented in terms of its preferred embodiment, herein depicted within the Figures.

1. Detailed Description of the Figures

A volumetrically operating titration device, generally noted as 10, is provided according to the preferred embodiment of the present invention. The device 10 includes a main unit 12 which has a front panel 14 with keypad 16 and full color display 18. The keypad 16 and display 18 provide functional controls for activation a pump mechanism 20 for volumetric addition of reagents. A carousel 21 of removable measuring units 22 are in fluid communication with the pump mechanism 20 for colorimetric or potentiometric titration. The carousel 21 is attachable to a base unit 24.

A noninvasive photo-probe or potentiometric probe 40 is further provide such as to be in operational

interaction with the removable measuring units 22. A noninvasive photo-probe 40 in accordance with the present invention may comprise a diode 42 adapted for emitting light within a desired range, and a photodetector used to measure light intensity within such range. Such a desired range may include, for example, light intensity from 350nm to lOOOnm.

The main control electronics of the device 10 is intended as being capable of compensating different light noises by means of said noninvasive photo-probe 40. By modulating light between 350nm to lOOOnm and at a

frequency higher than can be detected by any human eye (such as, for example, more than, 40Hz) , measurement can be accomplished in a manner that allows the observer to avoid the interference resulting from background light noise .

Measuring units for colorimetric titration may include several photo diodes placed, for example, inside a magnetic stirrer. In such a configuration, the

noninvasive photodetector may be placed under the

titration vessel 22, and with light emitted down through the vessel to the magnetic stirrer, for example. Several photo diodes may then be used to measure light intensity in different light ranges. The main control electronic board with the photo diodes may be placed inside the magnetic stirrer. In such a configuration a glass window in the magnetic stirrer may be shifted from the center of the stirrer in order to prevent the stirring bar from interfering with the light path from the diode to the chip .

The intensity of this light can then measured on several wavelengths and at the beginning of and during the titration.

The use of multiple photo diodes may further

provide for noise-corrected titration measurement. Such noises may be caused by many factors, including, inter alia: changes in diode intensity; background light noise (such as, for example, sunlight, shadows cast by a body passing by, environmental incandescent sources, etc.); or the presence of a mixing vortex.

The channel with the greatest change in intensity was normalized relative to the channel with the smallest change .

Thus, change in diode intensity and background light noise was almost totally compensated for. Even the presence of a vortex does not affect the measuring of the normalized intensity. As a result, the instrument could detect very slight color change, which cannot be detected by any human eye. Due to presence of near infrared channel information and a non-invasive probe, the

instrument can be used, for example, for titration with sediment formation or with temperature change. It can also be used for titration with absorbance change out of visible light range. So, new titration methods could be developed .

2. Operation of the Present Invention

According to the present invention, the titration device 10 with colorimetric measuring unit can be used not only for automation of well known colorimetric titrations but also for a titration with sediment

formation or with temperature change. It may also be used for a titration with absorbency change out of the visible light range, for example NIR or UV. So new titration methods can be developed. The intensity of this light can then measured on several wavelengths and at the beginning of and during the titration.

Thus, compensation for changes in diode intensity and background light noise is nearly total. Even the presence of a vortex does not affect the measuring of the normalized intensity. As a result, the instrument could detect very slight color change, which cannot be detected by any human eye. Due to presence of near infrared channel information and a non-invasive probe, the

instrument can be used, for example, for titration with sediment formation or with temperature change. It can also be used for titration with absorbency change out of visible light range. So, new titration methods could be developed .

In operation, due to presence of near infrared channel information and a non-invasive probe, the

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical

application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the

particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. Therefore, the scope of the invention is to be limited only by the following claims .

Claims

CLAIMS Having thus described the invention what is claimed as new and desired to be secured by Letters Patent is as follows :

1. A colorimetric titration system comprising:

a titration vessel;

a noninvasive probe including a diode adapted to emitting light in a selected range and modulated at a frequency higher than 40Hz, said probe positioned under said titration vessel such that light emitted from said diode is directed through said titration vessel; and

a photodetector for measuring the intensity of light emitted from said diode at the beginning of and during a titration.

2. The colorimetric titration system of claim 1, wherein said noninvasive probe includes a plurality of photo diodes adapted to measure light intensity in different light ranges; wherein said intensity of light emitted from said plurality of diodes is measured on more than one wavelength and at the beginning of and during the titration.

3. The colorimetric titration system of claim 2, wherein a channel with a greatest change in intensity is then normalized relative to a channel with a smallest change .

4. A volumetrically operating titration device

comprising :

a main unit providing functional controls for activation a pump mechanism for volumetric addition of reagents ;

a rotatable carousel of removable titration vessels each in sequential fluid communication with said pump mechanism for colorimetric or potentiometric titration; a noninvasive probe in operational interaction with at least one said removable measuring units

5. The volumetrically operating titration device of claim 4, wherein said noninvasive probe is a noninvasive photo-probe comprising a light source adapted for emitting light within a desired range and a photo detector for measuring intensity of said emitted light within said desired range.

6. The volumetrically operating titration device of claim 5, wherein said desired range comprises light intensity between from about 350nm to about lOOOnm.

7. The volumetrically operating titration device of claim 6, further comprising wherein control electronics in operational communication with said photodetector in a manner capable of compensating different light

noises .

8. The volumetrically operating titration device of claim 7, wherein said light source is adapted for

emitting light at a frequency higher than can be detected by any human eye.

9. The volumetrically operating titration device of claim 7, wherein said light source is adapted for

emitting light at a frequency higher than 40Hz.

10. The volumetrically operating titration device of claim 4, wherein:

said light source comprises photo diodes located inside a magnetic stirrer contained within said titration vessel and adapted such that light is emitted downward through said titration vessel; a transparent window formed in said magnetic stirrer and adapted for allowing passage of light emitting from said photo diode; and

said photodetector is positioned under at least one said titration vessel.

11. The volumetrically operating titration device of claim 10, further comprising:

a plurality of photo diodes for emitting light at different wavelengths, and

said photodetector adapted for measuring light intensity at said different wavelengths.

12. The volumetrically operating titration device of claim 10, wherein said window in said magnetic stirrer is positioned offset from a rotational center of the stirrer in order to prevent the stirring bar from interfering with the light path from the diode to the photodetector.

13. The volumetrically operating titration device of claim 11, wherein said window in said magnetic stirrer is positioned offset from a rotational center of the stirrer in order to prevent the stirring bar from interfering with the light path from the diode to the photodetector.

14. The volumetrically operating titration device of claim 12, wherein intensity of emitted light is

measurable at the beginning and during a titration.

15. The volumetrically operating titration device of claim 13, wherein intensity of emitted light is

measurable at several wavelengths and at the beginning of and during a titration.

16. The volumetrically operating titration device of claim 15, wherein a channel with the greatest change in intensity is normalized relative to a channel with the smallest change.

17. The volumetrically operating titration device of claim 9, wherein said rotatable carousel is adapted for automation of sequential titration operations.

18. The volumetrically operating titration device of claim 10, wherein said rotatable carousel is adapted for automation of sequential titration operations.

19. A method for implementing an automated volumetric titration comprising the steps: a. emitting a light into a titration vessel in a selected range and modulated at a frequency higher than 40Hz; and

b. measuring the intensity emitted from said light source and passing through said titration vessel at the beginning of and during a titration.

20. The method of claim 1, wherein said intensity of light emitted from said slight source and passing through a titration vessel on more than one wavelength.