WO2018056931A2

WO2018056931A2 - An electrode to be used in determination of phosphate and a method for manufacture of an electrode

Info

Publication number: WO2018056931A2
Application number: PCT/TR2017/000089
Authority: WO
Inventors: Yücel ŞAHIN; Özge KOYUN; Melih Beşir ARVAS
Original assignee: Sahin Yuecel; Koyun Oezge; Arvas Melih Besir
Priority date: 2016-09-21
Filing date: 2017-08-02
Publication date: 2018-03-29
Also published as: WO2018056931A3; GB2567993B8; GB2567993B; TR201613170A1; DE112017004744T5; GB2567993A8; WO2018056931A4; GB201902974D0; GB2567993A

Abstract

The invention is related to a method (500) developed to carry out the determination of phosphate anywhere desired, cost efficiently and readily without the use of enzyme and a molybdenum blue-modified electrode manufactured using this method (500).

Description

AN ELECTRODE TO BE USED IN DETERMINATION OF PHOSPHATE AND A METHOD FOR MANUFACTURE OF AN ELECTRODE

The Technical Field to which the Invention is related;

The invention is related to an electrode manufactured to be used in determination of phosphate and the method of manufacture of this electrode.

Previous Technique;

In order to enhance the life cycle and the diversity of species of living creatures in lakes, ponds and biological life parks, it is required to carry out phosphate control. Besides, phosphate has great importance in development of grains and other products in agriculture. In soils where the quantity of phosphate is high, the plants incur damages, the productivity reduces and, as a result of irrigations carried out, water cannot be carried correctly within the body of the plant because of the increased phosphate within the body of the plant, which results in decay in the plant. Although different indications are seen in general in the plant dependent on the species of the plant and the rate of deficiency in case of any deficiency in the quantity of phosphate, yellowing in aged leaves, thick and steep leaf appearance, scrub growth, bluish green or purple color formation are typical characteristics in particular. Due to the deficiency of phosphate in plants, the fruit set in the plants weakens and fruits ripen prematurely and malformation and cracks are formed in fruits. Due to all these reasons listed, determination of phosphate becomes crucial.

Before use of sensors in the technology having become widespread, the determination of phosphate was being performed using wet analysis and spectroscopic methods. However, these conventional methods used are the methods requiring high cost and qualified personnel, being time-consuming, needing more consumables, the determination point of which is insufficient (that is to say, the smallest concentration quantity that may be measured by the method is insufficient) and not offering in-situ analysis opportunities in determination of phosphate. Since the devices by which these methods are implemented are not practical and mobile, namely, portable, it is difficult to analyze the determination of phosphate in-situusing spectroscopic methods. In another method available in the state of the art in addition to these spectroscopic methods available in the state of the art, it is also possible to determine the phosphate being an electro- inactive and inorganic species by means of sensors the use of which increases gradually in the entire world. However, since enzyme or enzyme systems are used in manufacture of these kinds of sensors available, the use of these kinds of sensors is affected readily by temperature and changes in pH. Therefore, it is difficult to store the enzyme-based potentiometric sensors used for determination of phosphate under room conditions until the moment of their use without their structure being distorted.

Although the determination of phosphate is performed by means of sensors in the previous technique, it is difficult to determine the phosphate electrochemically due to the fact that phosphate is an electro-inactive species.

In the patent document with number US5252486 being in the state of the art, the flow injection analysis method is mentioned for inorganic phosphate.

Brief Explanation of the Invention: The objective of the invention is to manufacture of an electrode and realize the method of manufacture of this electrode in order for the determination of phosphate to be able to be made electrochemically in a correct and quick manner in solutions considered to be phosphate.

By means of the method which is the subject of the invention (500), a molybdenum blue- modified electrode has been manufactured to be used in determination of phosphate without the use of any enzyme.

When carbon-based electrode is used as the method of working in an application with the invention directed to the purpose, the electrode obtained is the molybdenum blue-modified carbon based. When inert metal electrode is used as the method of working in another application of the invention, the electrode obtained is molybdenum blue-modified inert metal electrode. According to the applications, the determination of phosphate is carried out swiftly and cheaply immersing any of these electrodes to the solution in which phosphate determination is intended to be made and using the differential pulse voltammetry method. The differential pulse voltammetry is the method in which the sensor response of the electrode prepared by means of the cyclic voltammetry method is examined. By means of the subject method, the determination of the phosphate being an electro-inactive species is carried out without the use of any enzyme, namely, as non-enzymatic. In measurements carried out by immersing molybdenum blue -modified carbon-based electrode or molybdenum blue-modified inert metal electrode to various samples by applications of the invention, simultaneous, quick determination of phosphate may be carried out without employing any qualified personnel.

Besides, using the molybdenum blue-modified carbon-based electrode obtained in an application with the invention, a modified sensor has been obtained. Using the molybdenum blue-modified inert metal electrode obtained in another application, a modified sensor has been obtained. With the use of carbon-based electrode, there are the advantages of this electrode like cost-efficiency and readily availability and disposability. Using the disposable carbon-based electrode, it is also possible to clean the electrode pollution resulting from oxidation and other materials.

Detailed Explanation of the Invention: Explanation of the Figures

Figure-1: The diagrammatic view of the three-electrode system used in the method.

Figure-2: The flow chart of the method of manufacture of the molybdenum blue-modified electrode, which is the subject of the invention.

Explanation of the references in the figures: For the invention to be understandable; the parts in the attached figures have been assigned reference numbers singly and the equivalences of these numbers have been given below:

1. Mechanism

10. Working electrode

1 1. Supportingelectrolyte

12. Counter electrode

13. Reference electrode

14. Voltage or Current Source / Measuring Device The molybdenum blue electrode, which is the subject of the invention, is obtained from a working electrode (10) by means of the method (500) which is the subject of the invention.

By coating a working electrode (10) to be used in determination of phosphate with molybdenum blue, a modified electrode has been obtained.

The method (500) which is the subject of the invention is applied in a three-electrode system (1). The three-electrode system (1) contains a reference electrode (13), a counter electrode (12) and a working electrode (10). The working electrode (10) is the inert metal electrode in an application of the invention. In another application of the invention, the working electrode (10) is a carbon-based electrode. After manufacturing a molybdenum blue-modified electrode from said working electrode (10), molybdenum blue-modified electrode may be used as a sensor to determine phosphate. Said sensor may be carried to places where analysis is intended to be made. Use of carbon-based electrodes as the working electrode (10) and the fact that these electrodes are cheap, disposable and modifiable are the great advantage. The invention is characterized by the modification of the electrode, the fact that molybdenum blue is coated to the working electrode in the beginning and obtaining the final electrode, namely, molybdenum blue electrode. Using the molybdenum blue electrode obtained, phosphate is determined. Using also inert metal electrodes, modification process may be carried out readily.

Enzyme has not been used in any of the solutions used in the method (500) which is the subject of the invention. In order for phosphate to be able to be analyzed (e.g. in the soil), the soil is required to be caused to undergo pre-treatment and be brought from solid state to liquid state, namely, be prepared for the analysis. The final medium obtained as a result of this preparation, namely, the medium in which the analysis is made, is the solution (sample) medium.

The molybdenum blue-modified electrode, which is the subject of the invention, is manufactured according to the following steps of the method (500):

Preparation (501) of the molybdenum blue at a previously determined percentage and the supporting electrolyte (1 1) consisting of the acid solution at a percentage completing this Application of a potential (502) to the working electrode (10) immersed to the supporting electrolyte (1 1) prepared in a potential range previously determined and at a scan rate previously determined

Coating (503) the molybdenum blue being an inorganic species to the working electrode (10) in the supporting electrolyte (11) medium with the effect of the potential applied

Manufacturing the molybdenum blue-modified electrode (504)

Removal (505) of the molybdenum blue-modified electrode from the supporting electrolyte (1 1) medium

- Immersing the molybdenum blue-modified electrode into a mixture containing polymer at a percentage previously determined and a polymer containing organic solvent at a percentage completing this percentage and having organic solvent and thus ensuring the permanence of the molybdenum blue on the molybdenum blue- modified electrode (506)

The percentage of the molybdenum blue mentioned at the step 501 of the method (500) is between the ranges of 5% to 50%.

The complementary percentage mentioned at the step 501 of the method (500) which is the subject of the invention is the optimum acid quantity. Not any electrode modification exists above and under this quantity.

The potential range applied to the working electrode (10) at the step 502 of the method (500) is -2 V to +2 V.

The complementary percentage mentioned at the step 506 of the method (500) which is the subject of the invention is that the organic solvent is at the rate complementing this rate in return for a previously determined polymer percentage. For instance, if the polymer percentage is 5%, organic solvent is 95%.

If carbon-based electrode (100) has been used as the working electrode (10) in one of the application of the invention, the electrode manufactured with the method (500) is the molybdenum blue carbon-based electrode. If inert metal electrode has been used as the working electrode (10) in another application of the invention, the electrode manufactured with the method (500) is the molybdenum blue inert metal electrode. By using the molybdenum blue-modified carbon-based or molybdenum blue inert metal electrode the manufacture of which is completed according to the applications of the invention as the sensor, determination of phosphate is carried out. The determination of phosphate is carried out by immersing one of said electrodes into the suspected solutions as there is phosphate in any of them and using the differential pulse voltammetry method afterwards.

The determination of phosphate is carried out by means of the working electrodes (10) prepared and using the differential pulse voltammetry method. The differential pulse voltammetry method is a highly useful method for determination of organic, inorganic and metallic ion speciesin trace amount. In this method, the pulses superimposed onto a voltage linearly increasing in a fixed intensity are applied to the working electrodes (10) in desired time ranges. In this method, the current is measured two times, one being right before the pulse application and the other being toward the end of the pulse application, namely, at in the situation where the capacitive current is approximately zero. The difference between the currents is obtained with a voltammogram in the form of a peak when transferred to graphic against the voltage.

In order for the molybdenum blue coated onto inert metal electrode or carbon-based electrode used as the working electrode (10) according to the applications of the invention to be able to remain permanently on the electrode, the molybdenum blue-modified electrode is immersed into a mixture containing polymer at a rate of 5% to 50% and containing organic solution at a rate complementary to this. By being coated with molybdenum blue permanently after this procedure, working electrodes (10) have been made usable in determination of phosphate.

When determining the phosphate of the molybdenum blue-modified electrode manufactured using the method (500) which is subject of the invention, it is ensured that the prepared molybdenum blue-modified electrodes are immersed into the polymer and organic solution medium and made ready for use by being dried. Then, the solution of the analyte having phosphate in its content is prepared and the determination of phosphate is carried out by the differential pulse voltammetry method after installing the 3 -electrode system.

Using the molybdenum blue-modified electrode manufactured using the method (500) which is subject of the invention; the determination of phosphate may be carried out readily without the need for enzyme. Besides, the molybdenum blue-modified electrode obtained using the method (500) which is subject of the invention may be used as a sensor for determination of phosphate. It is very important that the supporting electrolyte (1 1) used in the method (500) which is subject of the invention is coated onto the surface of the working electrode (10) in a very good way. As the supportingelectrolyte (1 1 ), molybdenum blue between 5% to 50% and an acid solution medium complementing this have been used. The method of manufacturing electrode (500) developed with the invention has many advantages compared to the other methods of manufacturing electrodes. The most important one among these advantages is the fact that enzymatic based materials are not used in preparation of the molybdenum blue-modified electrode mentioned within the scope of the invention. In the invention, the molybdenum blue being a chemical species is being modified onto the surface of the electrode. Although working with electrodes coated with enzymes is difficult, their structures are distorted and may be denatured due to atmospheric conditions such as temperature.

Thus, since enzyme is not used in the invention, the duration that deformation comes into existence in the stability and structure of the molybdenum blue-modified electrode manufactured is longer than that of enzymatic based molybdenum blue-modified electrodes. The molybdenum blue-modified electrode manufactured using the invention may be used as sensor. Thus, the phosphate sensors obtained within the scope of the invention are the sensors prepared with voltammetric method having good limit of determination of phosphate, not containing enzyme and being able to be stored readily without their structures being distorted under room temperatures.

Applicability of the invention to the industry

The method (500) which is the subject of the invention is a method by which phosphate analysis is performed with its mechanism not containing enzyme, namely, with its non- enzymatic mechanism. By means of this method, the analysis of many samples may be carried out within a very short period of time and determination of phosphate may be facilitated in field of the industry. Furthermore, by means of this method (500) which is the subject of the invention, the analysis of phosphate may be realized without application of the pre-treatment steps applied to devices used in other methods of determination. To evaluate the subject invention financially, graphite being the basic material of one of the phosphate sensors prepared in this method is even more cost-efficient compared to the commercial electrodes. Thanks to the molybdenum blue-modified electrode developed with the method (500) which is the subject of the invention and the easily portable sensor obtained using this electrode, analyses may be made swiftly, without the need for high cost in-situ, namely, anywhere desired in agriculture, pharmaceutical and food industries and other industries. By means of the invention, solutions may be brought to problems encountered frequently in determination of phosphate. In-situ, swift, cost-efficient and easy analyses may be carried out in determination of quantity of phosphate being important for fertilization.

Further, the invention may be used readily in quantitative and qualitative analysis of many molecules containing phosphate in pharmaceutical industry and food industry. The molybdenum blue-modified electrode which is the subject of the invention and the sensor obtained from this sensor may be transformed into a portable sensor like glucometers used commercially.

The invention is not limited to the applications explained above and a person who is qualified in the technique may put forth different applications of the invention readily. These should be evaluated within the scope of the protection of the invention requested by means of the claims.

Claims

The method (500) of manufacturing molybdenum blue-modified electrode, which is characterized with the steps of:

Preparation (501) of the molybdenum blue at a previously determined percentage and the supporting electrolyte (1 1) consisting of the acid solution at a percentage completing this

Application of a potential (502) to the working electrode (10) immersed to the supporting electrolyte (1 1) prepared in a potential range previously determined and at a scan rate previously determined

Coating (503) the molybdenum blue being an inorganic species to the working electrode (10) in the supporting electrolyte (1 1) medium with the effect of the potential applied

Manufacturing the molybdenum blue-modified electrode (504)

Immersing the molybdenum blue-modified electrode into a mixture containing polymer at a percentage previously determined and a polymer containing organic solvent at a percentage completing this percentage and having organic solvent and thus ensuring the permanence of the molybdenum blue on the molybdenum blue- modified electrode (506)

in order to carry out the determination of phosphate anywhere desired, quickly, cost efficiently and readily.

The method (500) of manufacturing molybdenum blue-modified electrode as in claim 1 which is characterized by the percentage of the molybdenum blue mentioned at the step 501 being between the ranges of 5% to 50%.

The method (500) of manufacturing molybdenum blue-modified electrode as in claim 1 which is characterized by use of carbon based electrode (100) as the working electrode (10) mentioned at the step 502.

The method (500) of manufacturing molybdenum blue-modified electrode as in claim 1 which is characterized by use of inert metal electrode as the working electrode (10) mentioned at the step 502.

5. The method (500) of manufacturing molybdenum blue-modified electrode as in claim 1, which is characterized by the potential range applied to the working electrode (10) at the step 502 being between -2 V to +2 V.

6. The method (500) of manufacturing molybdenum blue-modified electrode as in claim 1 which is characterized by the complementary percentage mentioned at the step 506 being that the organic solvent is at the rate complementing this rate in return for a previously determined polymer percentage.

7. A method (500) in any of the claims above which is characterized by non-use of enzyme in all solutions used.

8. An electrode manufactured according to a method in any of the claims above.

9. An electrode obtained by coating a working electrode (10) with molybdenum blue to be used in determination of phosphate.

10. An electrode as in claim 9 in which the working electrode (10) is inert metal.

1 1. An electrode as in claim 9 in which the working electrode (10) is carbon based.

12. A portable sensor obtained from a molybdenum blue electrode as in any of the claims 8 to 11 to be used in determination of phosphate.