SI21110A - Method and optical sensor for continous measurement of dissolved hydrogen peroxide - Google Patents

Abstract

By using a method and optical sensor for continuous measurement of dissolved hydrogen peroxide, the problem of interaction between an indicator and an analyte is solved and spectrophotometric measurement of hydrogen peroxide in a wide range of concentrations made possible. The specific of the method is that it starts with mixing of indicator and ethanol in a magnetic stirrer. This step is followed by addition of tetra-methoxy silane, by mixing in an ultrasonic mixer for the period of 5 minutes prior to the addition of the catalyst water solution of HCl and finally by a 5-minute mixing in the ultrasonic mixer. Next, the solution has been gelled at a room temperature in small closed vessels, before sensor membranes are made by immersion of round glasses in the solution (sol) and the films dried for 5 days at room temperature initially and then for further 24 hours at 50 degrees Celsius.

Description

The field of technology

The invention falls within the field of testing and analysis of materials by optical means, or more precisely, methods and optical sensors as miniature devices that allow continuous measurement of the analyte through the optical properties of the indicator.

A technical problem

The technical problem is a simple process and the manufacture of a miniature chemical optical sensor in which the interaction of the indicator with the analyte enables spectrophotometric measurement of hydrogen peroxide over a wide concentration range. The interaction is reflected in the optical properties of the indicator, which are reflected in changes in the absorbance intensity, allowing the detection of rapid changes in concentration. It is an object of the invention to provide a manufacturing method for the preparation of such a sensor with a sensor membrane, in which the indicator will not be flushed upon contact with the analyte and will have high sample sensitivity and good repeatability of preparation of the sensor membrane. The sensor membrane must have a wide concentration range, fast response times, stability, reversibility, easy immobilization of the indicator into sol-gel material and easy preparation of the sensor.

The prior art

The published and patented products so far mainly cover the determination of hydrogen peroxide in solution. U.S. Pat. No. 4,647,532 describes a highly sensitive method for the determination of H2O2 by chemiluminescence without interference from living organism components. The determination is based on the reaction of H2O2 with an oxidized non-fluorescent substance in the presence of an oxidized catalyst that converts the non-fluorescent substance into a fluorescent form that reacts with an oxalic acid diester and H2O2 in the presence of an inhibitor that inactivates the oxidized catalyst and measures the amount of light emitted.

US 5,094,943 describes the colorimetric determination of H2O2 resulting from the oxidase reaction of H2O2 produced by the addition of chromogen. The reaction of chromogen and H2O2 in the presence of peroxidase, cited in US 4,916,058, and measurement of absorbance in the visual field also involves colorimetric determination.

U.S. Patent 4,794,079 provides H2O2 with fluorogenic diquinolone and dihydrocoumarin, which yield highly fluorescent products upon oxidation with H2O2 in the presence of peroxidase-active substances.

The following EU patent 0 585 212 A2 describes the preparation of a sensor membrane of different polymers: cellulose, ethyl acetate and polystyrene and the indicator Ruthenium complex.

Other common methods for determining H2O2 in addition to chemiluminescence [1] and spectrophotometry [2] include spectrofluorometry [3], continuous continuous flow analyzes [4] and flow injection [5].

[1] P. Van Zoonen, D.A.Kamming, C. Gooijer, N.H. Velthorst and R.W. Frei, A solid-state chemiluminescence detector for hydrogen peroxide based on immobilized luminophore, Analytica Chim. Acta, 174, pp. 151,1985.

[2] P.A. Clapp and D.F. Evans, Spectrophotometric determination of hydrogen peroxide with leuco Patent Blue Violet, Analytica Chim. Acta 243, pp.217,1991.

[3] M. Zhou, Z. Diwu, N.P. Voloshina and R.P. Haugland, A stable nonfluorescent derivative of resorufin for the fluorometric determination of gossip hydrogen peroxide, Anal.Biochem., 253, pp. 162,1997.

[4] D. Stories, P.J. Vorsfold, R. Fauzi, Determination of hydrogen peroxide in sea water by flowinjection analysis with chemiluminescence detection, Analytica Chim.Acta, 298, pp.121,1994.

[5] D. Janasek, U. Spohn, D. Becmann, Novel chemiluminometric H2O2 sensor for selective flow injection analysis, Sensors and Act. B 51, pp. 107,1998.

Description of solution to a technical problem

The essence of the method and the optical sensor for continuous measurement of dissolved hydrogen peroxide is that the sol-gel material was selected for the polymeric base due to its optical permeability, mechanical stability, chemical inertness, flexibility in forming the sensor configuration and as an Meldola Blue indicator, which is immobilized to a polymer base with a doping technique, with the dye leaching being less than that of other immobilization techniques. Meldola Blue is used as the most appropriate indicator because it eliminates most interferences and has a high absorption and solubility.

The method and optical sensor for continuous measurement of dissolved hydrogen peroxide according to the invention will be described below with the help of figures showing:

Figure 1 - Schematic of the process for preparing the sensor membrane.

Figure 2 - Response of the sensor membrane to dissolved H2O2 at pH 7 and its reversibility on Na2S20s exposure.

As shown in Figure 1, the preparation of the optical sensor fabrication with the sol-gel sensor membrane begins by mixing the indicator and ethanol on a magnetic stirrer. This step is followed by the addition of tetramethoxy Silane followed by stirring on an ultrasonic mixer for 5 minutes before adding an HCI aqueous solution catalyst and finally mixing for 5 minutes on an ultrasonic mixer. The solution is gelled at room temperature in sealed containers before sensor membranes are made by immersing the round slides in the solution (salt). The films were first dried at room temperature for 5 days and then at 50 ° C for 24 h.

The reaction of the indicator with H2O2 is reflected in the optical changes that result in a change in absorbance that is proportional to the H2O2 concentration. Absorbance was measured with a spectrophotometer (Ocean Optics SD2000). The halogen bulb served as the light source. The light travels through the optical fiber to the flow cell into which the sensor membrane is mounted, and then through the second optical fiber to the detector in the spectrophotometer. The supply of H2O2 was made possible by a peristaltic pump whose rate was constant at 1 ml / min.

The graph in Figure 2 shows the responsiveness of the sensor membrane of the invention to dissolved H2O2 at pH 7 and its reversibility upon exposure to Na2S20s. The relative change in the signal (ΔΙ) to a concentration of 10 ^"8 and 10 ^{of 1} M, 20% of the total signal change, the response time of TGS (time to reach 95% of the total signal change is 1.5 min). The sensor membrane exhibits -95% of the signal reversibility obtained with 10 ' ¹ and -90% with 10-M hydrogen peroxide.

The procedure below for the preparation of the sensor membrane according to Figure 1 is provided.

Example 1:

mg of the dye is dissolved in 2.5 ml of ethanol, 2 ml of tetramethoxysilane and 1 ml of HCl (pH = 3) are added. After gelation in sealed containers, membranes are made by dipping them onto the surface of the round slides (φ 20 mm). It is air-dried at room temperature for 5 days and at 50 ° C for 24 hours.

CONCLUSIONS

1. The method for the determination of H2O2 shall include:

a) simple preparation of the sensor membrane by immobilization of the indicator into the polymer base

b) The sensor membrane referred to in point a) was prepared from sol-gel material

c) Meldola Blue is the most appropriate indicator for immobilization into sol-gel material

2. The response of the sensor membrane according to Decision 1 to H2O2 was determined by measuring the absorbance.

3. The reversibility of the sensor membrane was achieved by exposure to the Na2S2Os solution.

4. The sensor membrane made according to decision 1 is suitable for the determination of dissolved H2O2 over a wide concentration range of 10-® to 0.7 M.

The optical membrane sensor membrane for hydrogen peroxide measurement was developed by immobilizing the indicator redox dye into sol-gel material. The dye in direct contact with the analyte, hydrogen peroxide, alters the optical properties being measured. Indicators immobilized in sol-gel material. The sensor membranes showed large signal changes and fast response times over a wide concentration range of 10-® - 0.7 M as shown in Figure 2.

Claims (2)

PATENT APPLICATION A method for the continuous measurement of dissolved hydrogen peroxide, characterized in that it begins by mixing the indicator and ethanol on a magnetic stirrer, followed by the addition of tetra-methoxy silane followed by stirring on an ultrasonic stirrer for 5 minutes before adding the aqueous catalyst. HCI solutions and finally stirring for 5 minutes on an ultrasonic mixer to gel at room temperature in closed containers before sensing membranes are made by immersing the round glasses in solution (salt) to allow the films to dry at room temperature for 5 days and then for another 24 h at 50 ° C. 2. Optical sensor for continuous measurement of dissolved hydrogen peroxide made according to the method of claim 1, characterized in that the sensor membrane is made by dissolving 10 mg of dye in 2.5 ml of ethanol, to which 2 ml of tetramethoxysilane and 1 ml of HCI (pH are added). = 3) that, after gelation in sealed containers, membranes are made by immersion on the surface of round slides (φ 20 mm), followed by drying for 5 days in air at room temperature and then for 24 hours at 50 ° C.