CS201167B3 - Device for executing the continuous amperometric analysis - Google Patents

Description

The present invention relates to an apparatus for carrying out a continuous amperometric analysis of a system of at least two electroactive substances according to U.S. Pat. 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 a single electroactive component of the mixture is reacting on its surface, the current flow, intermediate 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 at least two electroactive components and completely precludes the analysis of a mixture of substances in which one component provides multiple polarographic waves, some of which coincide with the β wave of the other component in the mixture.

This limitation of the amperometric analysis eliminated the method of continuous amperometric analysis according to MS. No. 185099, according to which a droplet electrode current is measured at the end of each droplet's life and at the droplet drop point, the jump potential changes to a value where a current proportional to the electroactive component or sum or other linear function can be observed concentration in the system. Suitable potential values are, for example, the areas of the limit currents on classical polarograms.

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The current values at the selected potentials and ee at the end of life measure each drop, appropriately amplify and store 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 an apparatus for practicing a method of continuous amperometric analysis of a system of at least two electroactive substances according to U.S. Pat. This device consists of a cyclically variable voltage source connected to an input terminal of an electronic polarograph or potentiostat, the output of which is connected to a polarographic vessel to which a current to voltage converter is connected to measure the instantaneous current of the droplet electrode. The apparatus further comprises at least two analogue converting-type memory amplifiers provided with data outputs and connected by their addition inputs to a voltage to voltage converter and by its control inputs to a control logic and timer, to which inputs are connected a knock defining mercury electrode and a control input. sources of cyclically stepped variable voltage. The summation inputs of each of the analogue memory amplifiers are connected to the outputs of the other analogue memory amplifiers by potentiometers. The device may also be arranged such that an evaluation analog circuit is provided between the current to voltage converter and the input of at least one of the analogue memory amplifiers to obtain a signal proportional to the concentration of one component of the mixture to be diffused, for example an AC adapter for polarography.

The attached drawing shows a block diagram of an exemplary embodiment of the device according to the invention. The device shown is intended to simultaneously determine the concentration of three electroactive components in a mixture. It comprises a cyclically variable voltage source 1, the course of which is illustrated by curve 2 for illustration, and which is applied to the input terminal of the electronic polarograph or potentiostat 3, to whose output a polarographic vessel 4 containing a mercury drop electrode and a counter electrode is connected. A three-electrode system can also be used. A current to voltage converter 6 is included in the polarizing current circuit to measure the instantaneous current of the droplet electrode. To its output are connected the input terminals of three analogue memory amplifiers 6, 7, 8, provided with data outputs 12, 13. 14. The summation inputs of each of the analogue memory amplifiers 6, 8, 8 are connected via tensiometers 9, 10, 11 The device further comprises a control logic and timing element 15. By means of a knocker 16, the mercury droplet synchronizes with the step change of the voltage generated in the source of a cyclically stepwise variable voltage 1 and simultaneously controls the droplets gradually at the end of the lifetime. analogue memory amplifiers 6, 7, 8.

Compared to MS. The order and magnitude of the voltage of the individual stages of the waveform, as shown for example by curve 2, can always be selected so that during one measuring cycle the current flowing through the next drop or indicated by the analog evaluation circuit is always greater than the flowing currents. previous drops in the same measurement cycle. For example, there may be a case where during growth

The first drop is the most positive potential and the current is proportional to the concentration of only one component. The current flowing through the next drop growing at a more negative potential then depends not only on the concentration of the component registered by the previous drop, but also on the concentration of the next component. With the last drop growing at the most negative potential, all three components are reduced and the current is therefore linearly dependent on the concentration of all these components. Consequently, the concentration of any substance in the mixture is proportional to the current corresponding to the component multiples recorded during all previous drops of the same measuring cycle. This reading and multiplication by the appropriate constants is made possible by the use of inverting-type analog memory amplifiers whose output voltage always changes in the opposite direction to the input voltage during the sampling interval and by inserting the potentiometers into the analog memory amplifier network.

Thus, the described apparatus combines both the operation of the memory amplifiers and the analog evaluation network. Also, switching the number of steps and adjusting the instrument for analyzing different sets of substances are quite simple.

If, in at least one step of the measuring cycle, an electrical signal proportional to the concentration of one component in the mixture other than the diffuse current is evaluated, for example AC amplitude at superposition of low AC voltage across the potential waveform shown by curve 2, one of the analogue memory amplifiers 6, 7, 8 of the respective analog evaluation circuit 17, 18, 19, in the present example, an AC current detector.

The number of steps in the measuring cycle is determined by the number of electroactive components of the mixture to be determined, which also controls the number of analogue memory amplifiers and potentiometers. This number is fixed or variable by the cell and is determined by setting the number of steps of the control logic and timing element 15.

The device can easily be adapted to act as a polarograph, providing a classical and derivative polarogram. The adjustment is performed using, for example two analog memory amplifiers 6, 7, substituting sources cyclically stepwise variable voltage one source of linearly increasing or stepwise uniformly increasing voltage, for example a digital-to-analog converter, and adjusting the potentiometer 9 ^to unity gain of the signal from the analog memory amplifier 6 into The output 12 from the analog memory amplifier 6 then represents a classical polarogram, the output 13 from the analog memory amplifier 7 a derivative polarogram.

The equipment can be used for automatic regulation of chemical reactors, fermentation tanks, water management equipment and other chemical-technological equipment, where the concentration of raw material products, intermediate or harmful by-products can be monitored by polarographic and amperometric analytical method.

Claims (2)

SUBJECT OF THE INVENTION Apparatus for carrying out a continuous amperometric analysis of a system of at least two electroactive substances according to the author's certificate No. 185099, characterized in that it consists of a source of cyclically variable voltage (1) connected to the input terminal of the electronic polarograph or potential. a polarographic vessel (4) is connected to the output, to which a current to voltage converter (5) is connected for measuring the instantaneous current of the drop electrode, to which at least two inverting-type analogue memory amplifiers (6, 7, 8) are connected by their addition inputs; provided with data outputs (12,13,14) and whose control inputs are connected to a control logic and timing member (15) to which inputs are connected both a knock 116 for determining the mercury electrode dripping and a control input of a cyclically stepped variable voltage source (1) ), with the summation inputs of each analog The memory amplifiers (6,7,8) are connected to the outputs of the other analog memory amplifiers (6,7,8) using potentiometers (9,10,11). Device according to claim 1, characterized in that an evaluation analog circuit (17,18,19) is provided between the current to voltage converter (5) and the input of at least one of the analogue memory amplifiers (6,7,8) to obtain another signal. proportional to the concentration of one component of the mixture being determined, other than the diffusion current, for example an AC adapter for polarography.