CS200652B3 - Equipment for execution of continuous amperemetric analysis - Google Patents

Description

The invention relates to a device for performing a continuous amperometric analysis of a system of at least two electroactive substances according to the basic author's certificate No. 185099

Amperometric analysis of the solution of substances is based on the fact that the current flowing from the solution to the droplet electrode is directly or indirectly proportional to the rate of transfer and conversion of substances on the electrode surface. If the sample to be examined contains only one electroactive component, or if the mercury droplet electrode potential is such that only one electroactive component of the mixture is reacting on its surface, the current flow, medium or instantaneous at the appropriate point in the droplet life, is approximately components in solution. However, this condition greatly limits the possibility of continuous amperometric analysis of mixtures of two or more electroactive substances and completely excludes the analysis of a mixture of substances in which one component provides multiple polarographic waves, some of which coincide with the wave of another component in the mixture.

This limitation of the amperometric analysis has eliminated the method of continuous amperometric analysis according to Se. No. 185099, according to which a droplet electrode current is measured at the end of each droplet's life and at the droplet dripping point, changes the potential by jump to one of the values at which a current proportional to the electroactive component or sum or other linear function concentration in the system. Suitable potential values are, for example, the limit current areas on classical polarogrameeh. Hod200 652

200,652 notes of currents at selected potentials are measured, appropriately amplified at the end of the lifetime of each drop, and stored in as many memory amplifiers as many different substances are determined. After each measurement cycle, the values stored in the memories are processed in an analog computer network to obtain signals proportional to the concentration of the individual components.

SUMMARY OF THE INVENTION The present invention provides a device for practicing the above-mentioned method of continuous amperometric analysis of a system of at least two electroactive substances which, however, uses analogue-digital measurement techniques instead of analog sampling and evaluation circuits. According to the invention, the apparatus comprises a polarographic vessel connected to an electronic polarograph or potenciastat, the input of which is connected to a digital-to-analog converter for generating a programmed cyclically variable voltage step and to an analog-to-digital converter to measure the instantaneous droplet electrode current. The apparatus further comprises a microprocessor to which an analog-to-digital converter is connected and to which outputs a digital-to-analog converter, a drop-drip control knob and a peripheral data output device, the microprocessor having an ee written memory, data memory and working memory. intermediate results and input devices. The device can also be adapted according to the invention such that an analog evaluation circuit is provided between the electronic polarograph or potentiostat and the analog-to-digital converter to obtain a signal proportional to the concentration of one of the components of the analyte other than the diffuse current, for example an AC polarography adapter.

The attached drawing shows a block diagram of one embodiment of the device according to the invention. This device comprises a simple electronic polarograph or potentiostat 1 and a two-electrode or three-electrode polarographic container 2 with a mercury drop electrode. The output signal from the electronic polarograph or potentiostat 1, proportional to the current flowing through the polarographic vessel 2, is converted in the fast analog-to-digital converter 3 into a digital signal which enters the microprocessor 6. This microprocessor 6 performs all further processing of the obtained data, i.e. multiplying the currents by calibration and stoichiometric constants, subtracting the adjusted current data of successive drops from each other, and optionally introducing further numerical corrections such as charging current, correction for a non-linear calibration curve, etc. The same microprocessor 4 also controls the sampling and dripping points of mercury via the knocker 2, generates a cyclically step-by-step control voltage for the electronic polarograph or potentiostat 1 via a digital-to-analog converter 6 and finally controls the data output by the peripheral device 8. is indicated in the drawing 10. The microprocessor is equipped with a program memory 6, a data and intermediate result memory 2, and an input device 11 to start and enter instructions for controlling the operation of the device. and to calculate the results.

If, in at least one neck of the measuring cycle, an electrical signal proportional to the concentration of one of the components of the mixture being analyzed is diffuse current, for example AC amplitude at superposition of low AC voltage over a potential waveform, for example waveform 10, an electronic switch and a corresponding analog evaluation circuit, in this case an AC component detector.

200 652

Particular advantages of the described apparatus include, in particular, the great ability to adapt the apparatus to the various needs arising from the analysis of various systems. Changes can be made by interfering with the program or by changing the constants inserted into the microprocessor 4. The device also allows for more complex corrections, such as calibration, charge current correction, etc .; the number of current amplitude samples per drop can be greater than 1.

The device according to the invention can also very easily be adapted to operate as a polarograph providing simultaneously both the classical and the derivative. The adjustment consists in storing in the memory with the written program 6 a program for generating incrementally increments of voltage for the digital-analog converter 5 and for calculating the current difference of two successive drops.

The device according to the invention can be used for the automatic control of the operation of chemical reactors, fermentation tanks, water treatment facilities and other chemical technology devices in which the concentrations of raw material products, intermediate or harmful by-products can be monitored by polarographic and amperometric methods.

Claims (2)

SUMMARY OF THE INVENTION 1. Apparatus for carrying out a continuous amperometric analysis of a system of at least two electroactive substances according to author's certificate No 185099, employing an analogue-to-digital measuring technique, characterized in that it comprises a polarographic vessel (2) connected to an electronic polarograph or potentiostat (1); an analog-digital converter (3) for measuring instantaneous current values of the droplet electrode is connected to the input, the device further comprising a microprocessor (4) to which the input is connected analogously - a digital converter (3) and to the outputs of which a digital-analogue converter (5), a drop drip control knob (9) and a data output peripheral device (8) are connected, the microprocessor (4) having a program memory (6) ), data memory and work interim results (7) and input devices (11). Device according to claim 1, characterized in that an analog evaluation circuit is provided between the electronic polarograph or potentiostat (1) and the analogue-to-digital converter (3) to obtain a signal proportional to the concentration of one of the components of the mixture being diffused. AC adapter for polarography.