RU2442976C2 - Method for production of highly stable sensitive element of hydrogen peroxide sensor - Google Patents

Abstract

FIELD: analytical chemistry.

SUBSTANCE: method involves ferric ferrocyanide being stabilized with nickel hexacyanoferrate, wherein the gradual sedimentation of ferric ferrocyanide and nickel hexacyanoferrate is performed.

EFFECT: production of sensors with high sensitiviy, selectivity and high signal stability.

1 dwg, 2 dwg, 2 ex

Description

The invention relates to a method for preparing a sensor element for hydrogen peroxide. In particular, to the stabilization method of Prussian blue, which is an electrocatalyst for the reduction of hydrogen peroxide, nickel hexacyanoferrate.

The determination of hydrogen peroxide is an important analytical task for clinical diagnosis, environmental monitoring and in various industries. Its content must be determined in groundwater and precipitation, where it gets as a result of emissions from industry and nuclear plants, as well as in the food industry.

To date, the most effective sensitive element for determining hydrogen peroxide is Prussian blue - iron (III) hexacyanoferrate (II) [1]. Inert electrodes (platinum, gold, glassy carbon) modified by Prussian blue are widely used in the construction of hydrogen peroxide sensors and biosensors containing immobilized oxidases as a biosensitive element [1].

During the interaction of Prussian blue film and the determined hydrogen peroxide, the latter decomposes to OH ^- hydroxide ion. At low concentrations of hydrogen peroxide, its effect on the properties of the sensor is negligible. However, during continuous measurements, a significant amount of hydroxide ions can form, which leads to the gradual dissolution of the coating of Prussian blue from the electrode surface. For continuous monitoring of the content of hydrogen peroxide, sensors are needed that, along with high sensitivity and selectivity, have good reproducibility of the current signal, that is, they have high stability.

The invention consists in the following:

- a method for the joint deposition of a sensitive element (Prussian blue) and a stabilizer (nickel hexacyanoferrate) on the electrode surface for the manufacture of a highly stable sensor on hydrogen peroxide;

- a method is proposed for the sequential deposition of a sensitive element (Prussian blue) and a stabilizer (nickel hexacyanoferrate) on the electrode surface for the manufacture of a highly stable sensor on hydrogen peroxide.

Example 1

Electrochemical method of co-precipitation of Prussian blue and nickel hexacyanoferrate on the electrode surface

The joint electrodeposition of nickel hexacyanoferrate and Prussian blue was carried out in the potentiodynamic mode, when the potential applied to the working electrode was scanned from 0 to +0.75 V, the potential sweep speed was 50-100 mV / s for 5-20 cycles. The synthesis was carried out in a three-electrode cell containing a working electrode, a silver chloride reference electrode, and a glassy carbon auxiliary electrode. The growth solution contained 1 mM K ₃ [Fe (CN) ₆ ] and x mM NiCl ₂ and (1) mM FeCl ₃ (x from 0.1 to 0.9) in the background electrolyte with the composition 0.1 M KCl, 0.1 M HCl .

Then, the electrodes were cycled in the potential range from 0 to +1 V in the background electrolyte with a composition of 0.1 M KCl, 0.1 M HCl at a potential sweep rate of 40 mV / s for 20 cycles. After that, the electrodes were subjected to heat treatment at 100 ° C for 1 hour and cooled to room temperature.

The figure 1 presents a comparison of the current versus time in a constant flow of 1 · 10 ^-3 M H ₂ O ₂ for sensors with sensitive elements based on Prussian blue and Prussian blue stabilized with nickel hexacyanoferrate by co-precipitation from salt solutions. For mixed coatings, the inactivation constant of the catalytic coating was reduced by almost an order of magnitude — it was 5 · 10 ^-3 min ^-1 compared to 45 · 10 ^-3 min ^-1 for Berlin blue. In a constant flow of hydrogen peroxide to the electrode surface in 20 minutes, a sensor with a stabilized sensing element loses less than 10% of the value of the initial signal, while a sensor based on Prussian blue loses more than 35% of the signal in 10 minutes.

Example 2

Electrochemical method of sequential deposition of Prussian blue and nickel hexacyanoferrate on the electrode surface

Serial electrosynthesis of the catalytic layers of Prussian blue and the stabilizing layers of nickel hexacyanoferrate was carried out in various three-electrode cells. One of the cells contained a growth solution for the synthesis of nickel hexacyanoferrate: 1 mM K ₃ [Fe (CH) ₆ ] and 1 mM NiCl ₂ in the background electrolyte with a composition of 0.1 M KCl, 0.1 M HCl. The second cell contained a solution for the electrosynthesis of Prussian blue; salt concentrations were varied within 0.5–4 mM for both FeCl ₃ and K ₃ [Fe (CH) ₆ ]. The electrochemical deposition of the nickel hexacyanoferrate coating was carried out in the potentiodynamic mode, with a potential sweep from 0 to +0.75 V, the potential sweep speed was 50-100 mV / s for 1-5 cycles. The electrodeposition of Prussian blue was carried out in the potentiodynamic mode, with a potential sweep from +0.4 to +0.75 V, the potential sweep speed was 10-20 mV / s for 1-5 cycles. After deposition of one of the compounds, the electrode was rinsed with distilled water and transferred to another cell for subsequent application of the other compound. The total number of layers in the sensor element was from 2 to 20.

The stages of processing the electrodes after electrosynthesis are similar to those described in example 1.

Figure 2 shows that for a sensor with a sensitive element based on a coating of Prussian blue stabilized with nickel hexacyanoferrate by sequential electrodeposition, the signal is stable for 1 hour or more, while in the case of a sensor with an unstabilized sensitive element, more than 35 are lost % of the initial value of the signal. It was possible to lower the inactivation constant of the catalytic coating of Prussian blue stabilized by nickel hexacyanoferrate by successive electrodeposition by four orders of magnitude: for it, the constant was 5 · 10 ^-6 min ^-1 , while for Prussian blue - 4.5-10 · ^-2 min ^-1 .

All characteristics of the sensors were obtained from experiments conducted in the flow-injection test mode in a phosphate buffer (0.1 M KCl, 0.1 M KH ₂ PO ₄ , pH = 6.0). The flow rate of the buffer solution is 0.25 ml / min. Operating potential 0 V rel. Ag / AgCl / 1 M KCl.

Literature

1. Arkady A. Karyakin, Prussian Blue and Its Analogues: Electrochemistry and Analytical Applications. Electroanalysis (2001), 13, 813-19.

Claims (2)

1. A method of preparing a sensor element of the sensor for hydrogen peroxide, characterized in that, in order to increase the stability of the sensor element, Prussian blue is stabilized with nickel hexacyanoferrate. 2. The method of preparing the sensor according to claim 1, characterized in that in order to increase the stability of the sensor, use sequential precipitation of Prussian blue and nickel hexacyanoferrate.

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