CS200650B3 - Equipment for execution of continuous ampere metric analysis - Google Patents

Description

(54) Continuous amperometric analysis equipment

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 one electroactive component of the mixture is reacting on its surface, the current flowing is medium or instantaneous at a suitable point in the droplet life. 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 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 limit currents on classical polarogpameeh.

200 650

200 650

Current values at selected potentials ee at the end of life of each drop measured, appropriately amplified 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 concentration-proportional signals individual components.

SUMMARY OF THE INVENTION The present invention provides an apparatus for practicing the above method of continuous amperometric analysis of a system of at least two electroactive substances which, instead of using analog sampling and evaluation circuits, utilizes analog-to-digital measurement technology and fixed logic circuits. According to the invention, the device comprises a polarographic vessel connected to an electronic polarograph or potentiometer, the input of which is connected to an electronically controlled programmable source cyclically in stages of variable voltage and to an analog-to-digital converter β programmable sensitivity output. The analog-to-digital converter is connected, optionally via a memory member, to a digital arithmetic member for reading instantaneous current values of successive drops according to a predetermined program, which is connected to the connecting means and the output device. The apparatus further comprises a controller to the outputs of which a mercury droplet control knob is connected, an electronically controlled programmable power source cyclically in stages of variable voltage, an analog-to-digital converter, a digital arithmetic member, and a fastener. The device may also be adapted to incorporate an analog evaluation circuit between the output of the electronic polarograph or potentiometer and the analog-to-digital converter to obtain a signal proportional to the concentration of one component of the mixture to be diffused, e.g.

The drawing shows a block diagram of an exemplary embodiment of the device according to the invention. This device comprises an electronic polarograph or potentiostat 1 and a two-electrode or three-electrode polarographic container 2. The output signal, proportional to the instantaneous current value of the droplet electrode, is fed to an analog-to-digital converter g which measures the magnitude of the current just before the end of the droplet's life. The output digital signal is provided to a digital arithmetic element g which reads the instantaneous streams of successive drops according to a preset program as described in the description of the invention to CS. No. 185099. The resulting digital signal, the value of which contains data on the concentration of electroactive substances, is fed to the output device χ, for example a display and a punched tape punch, by means of the connecting means 6. The operation of the device is controlled by a controller 8 which includes a timer for dripping the drop by means of a knocker 11 and further controls the function of the digital arithmetic element g, the analog-to-digital converter g and the fastener. a variable voltage 9 into the electronic polarograph or potentioethat 1; an example of the course of such stress for the simultaneous determination of two components is indicated in the drawing by 10.

The described apparatus is particularly suitable for the determination of two electroactive components in a mixture. In order to determine a larger number of components, it is expedient to include in the analogue-to-digital conversion3

200 nik 2 ^{and the} digital arithmetic member 2 a memory member 4 comprising one or more memory locations.

In contrast to the continuous amperometric analysis method described in the description of the invention to U.S. Pat. No. 185099, simplification is achieved here. Indeed, the order and magnitude of the voltages of the individual stages of the waveform, for example the voltage waveform 10, can always be selected such that during one measuring cycle the current flowing through the next drop or indicated by the analog evaluation circuit is always greater than the currents flowing through the previous drops of the same measuring cycle. The concentration of any substance is then proportional to the current corresponding to the component determined in the respective part of the cycle, from which the currents recorded in all previous stages of the same measurement cycle are subtracted.

The set of analog-to-digital converter 3 and digital arithmetic element 6 must therefore calculate the difference of successive data multiplied by the appropriate stoichiometric and calibration coefficients. The multiplication can be done analogously by inserting the amplifier β by a variable gain in front of the analog-to-digital converter 3 or by controlling the sensitivity of the analog-to-digital converter J performed, for example, on the compensating converter by reference voltage. Multiplication can also be performed by placing the digital multiplier on the vatup of the digital arithmetic term j>. The calculation of the difference of the consecutive data is performed in the digital arithmetic element 2, for example by a digital adder or a reversible counter. A reversible counter is used when the output of the analog-to-digital converter J is serial, as is usual for voltage-frequency converters or dual-integration integration converters.

The switching of the programmed voltage is carried out by electromagnetic relays, stepping mechanisms, a digital-to-analog converter or electronic switches, which devices are controlled by an electromechanical programmer, counter or shift register with a fixed or adjustable number of steps.

The measuring cycle program can be modified using switches, memories, or a program board known in the art of analog computers.

If, in at least one measuring cycle step, an electrical signal proportional to the concentration of that component other than the diffuse current is evaluated to distinguish one component in the mixture, for example an AC amplitude at a low AC voltage superposition across a potential to the digital converter 3, an electronic switch and a corresponding analog evaluation circuit, in this case an AC current detector.

The number of steps in the measurement cycle is determined by the number of determined components of the mixture, which also controls the complexity of the digital arithmetic member 5 and the number of memory locations in the memory member 4.

The device according to the invention can also be easily adapted to operate as a polarograph providing both classical and derivative polarogram. For this purpose, instead of an electronically controlled 650K programmable source cyclically increments of variable voltage, the source is used linearly or evenly increments of increasing voltage, or a using a digital analog converter whose content changes by one each drop and with continuous analog-to-digital transmission. The 2-in-2 converter and the 2 ° Digital Arithmetic Membrane build a two-step measuring cycle.

The device according to the invention can easily be used for the automatic regulation of chemical reactors, fermentation tanks, water management 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 ampavometric analytical methods. The device provides directly digital signals suitable for automatic production control systems.

Claims (2)

P FILDHI I IN CALCULATION Apparatus for performing a continuous amperometric analysis of a system of at least two electroactive substances according to part a. No. 185099, which uses analog-to-digital measuring technique and fixed logic circuits, characterized in that it comprises a polarographic vessel (2) connected to an electronic polarograph or potenoioatate (1), to which an electronically controlled programmable source cyclically connected and a programmable sensitivity for measuring the instantaneous current values of the droplet electrode that is connected, optionally via a memory member (4), to a digital arithmetic element (5) to read the instantaneous currents after of successive droplets according to a predetermined program, further connected by a connecting means (6) and an output device (7), the device further comprising a controller (8), to whose inputs a dropping drop control knob (11) is connected, electronically controlled programmable zdro j cyclically in steps of variable voltage (9), analog-to-digital converter (3), digital arithmetic element (5) and connecting means (6), 2. Apparatus according to claim 1, characterized in that an analog evaluation circuit is provided between the output of the electronic polarograph or potentiometer (1) and the analog-to-digital converter (3) to obtain a signal proportional to the concentration of one component to be determined. AC adapter for polarography.