SU981882A1 - Ac polarograph - Google Patents

Description

The invention relates to a graphical analysis and can be used in devices for determining ultra-small impurity concentrations in high-purity substances, for example, by using an inverted volt meter.

An alternating current polarograph, containing a sinusoidal voltage generator, a phase shifter, a linear variable voltage generator, a potentiostat, a cell, a low-frequency amplifier, a phase detector, a filter, and a recorder, is known. The principle of operation of this device is based on the registration of the active component of the alternating current cell signal, caused by the electrochigly reaction of the detected impurity depending on the linear-varying voltage on the cell 1.

The disadvantage of this device is that the total cell current contains a large level of residual current - interference, which is determined mainly by the current flowing through the capacitance of the cell double layer and can exceed the signal current by tens and hundreds of times in amplitude .

Closest to the present invention is an alternating current polarograph containing a phase shifter, linear-varying and alternating voltage generators, a potentiostat, a cell, a phase detector, a filter, a recorder, and a key.

In this device, the compensation effect is achieved by the use of a phase shifter with a control

an input connected to the memory output of the device device, the input of which loads the output of the direct current amplifier through the contacts, the input of which is connected to the output of the filter. Zapogante-optimal phase shift occurs immediately before the start of the electrochemical reaction of the element being determined. The use of this device allows a 10–13 fold decrease in the slope of the residual current at the dissolution potentials of mercury and the release of hydrogen. However, during the removal of the polarogram

25 we are breaking the setting

phase by changing the capacity of the DOUBLE layer. This, in turn, leads to a violation of the ratio of the active energy component of the residual current and its capacitive component compensating for it and the deterioration of the residual alternating current compensation level. Therefore, with an increase in the sensitivity of the instrument, the slope of the characteristic, the residual current becomes significantly E1m, which also obstructs the analysis and limits the use of the instrument.

The purpose of the invention is to increase the sensitivity and accuracy of the device.

The goal is achieved by: chuo in a polarograph containing a phase shifter, linear and alternating voltage generators, half connected via a potentiostat to the anode of the cell, to the cathode of which a low-frequency amplifier is sequentially connected, phase detector DC connected through a key with a memory device, additionally introduced two adders, an integrator, two memory devices, four keys, and the output of the filter is connected to the input One first adder, the output of which through the first and second keys is connected to both additional processing devices, the outputs of which through the third and fourth keys are connected to the integrator input, the output of which is connected to the inputs of both adders, and the second input of the second totalizer is connected to the output of the main memory device, and the output - with the control input of the phase shifter.

The drawing shows a diagram of the proposed polographer.

Polarograph contains a generator 1 linearly varying voltage, loaded with a potentiostat 2 and a control circuit 3. A cell 4 and a phase shifter 5, WHICH ARE loaded by the generator of sinusoidal voltage b, are also connected to the potentiostat. A low-frequency amplifier 7, a phase detector 8, a filter and a recorder 10 are connected in series to the cathode of the cell.

A DC amplifier 11 is connected to the filter output, loaded through pin 12 by a storage device 13, the output of which is connected to the control input of the phase shifter through an adder 14, and the adder 15 is connected via keys 16 and 17 to storage devices 18 and 19, whose outputs are via keys 20 and 21 by: f connected to the input of the integrator 22, controlled by a key 23, the output of which is connected to the input of adders 14 and 15.,

Gender works as follows.

In the initial state, before the start of the polarographic analysis, the voltage on the storage devices 18 and 19 is set to zero, the keys 17 and 21 are closed, the keys 16 and 20 are open.

On cell 4, a linearly varying polarizing voltage is supplied from generator 1 through a potentiostat 2, and alternating voltage is applied from generator b through a phase shifter 5.

The alternating current flowing through the cell is converted into an amplifier 7S voltage and fed to the input of the phase detector 3. The pulsating voltage from the detector output is smoothed by filter 9 and fed to the recorder 10.

The polarograph operates in two modes, and the first mode of operation of the second mode of operation of the PCBrograph passes when the linear-varying voltage reaches a potential element close to the potential of the beginning of the electrochemical reaction. The first mode of operation - mode c1 phase adjustment - keys 12 and 23 are closed. In this case, a constant voltage from the output of the filter 9 is amplified by a voltage switch, a disconnector 11, and through contact 12 and a storage device 13 is fed to the control input of the phase shifter 5.

In this case, the phase adjustment occurs until the residual current on the recorder is equal to zero.

In the phase self-tuning mode, the integrating capacitance of the integrator 22 is shorted by pin 23, and the voltage at the second input of the adder is 14 zero. The transition from the first mode to the second mode, in which the projecTu1T measurement of the electrochemical peak current and the adjustment of the compensator. Phase shift, is carried out. i by opening the keys 12 and 23. When the contacts 12 and 23 are opened, the memory 13 remembers the control voltage of the phase shifter, established in the first mode and corresponding to the full compensation of the residual current. After a further change of the polarizing voltage, an additional phase shift D (p arctan RjCOAl g.c) occurs where Rj- is the uncompensated voltage resistance;

 - circular frequency alternating voltage; After double capacity change

lay

This leads to the fact that the residual current component is undercompensated or overcompensated capacitance component. And with the increase; the sensitivity of the device is the slope of the uncompensated residual current rise.

Claims (1)

To reduce the slope of the residual current characteristic in the proposed polarograph, a phase shift compensator is used, which, after the end of the electrochemical reaction of the determined element, stores a voltage proportional to the level of residual current and then uses it to control the phase shifter that compensates for the voltage. In a polygraph, this is implemented as follows. After the end of the electrochemical reaction of the detected impurity, the voltage from the output of the filter 9, proportional to the uncompensated part of the residual current, goes to the first input of the adder 15. When the first polarogram is removed, the zero voltage is applied to the integrator 22. From the output of the adder 15, the voltage goes through the key 17 to the memory 18 and is remembered by the key 17 when simultaneously the keys 12, 16, 20 and 23 close, and the key 21 opens. In the repeated analysis in the phase self-tuning mode, the pp-graph works similarly to the first analysis, and in the measurement mode, the adder 14, together with the voltage from the memory device 13, supplies the integrator 22 with a compensating linear voltage, the slope of which depends on the residual current level stored the storage device 18 in the previous analysis. At the same time, the voltage from the filter 9 is fed to the adder 15 and summed with the compensation from the integrator 22. The signal from the output of the adder 15 is fed through the key 16 to the memory device 1 and is remembered by it when the key 16 is opened. At the same time the keys are 12, 17, 21 and 23, and the key 20 is disconnected. Due to the time and temperature drift, a change in the magnitude of the residual current for each field of the horizon occurs. Therefore, it is necessary to adjust the setting of the phase shift compensator before shooting each half of the program. In the third field removal: in the first mode, the polarograph operates similarly to the first survey, and to the measurement mode, the adder 14 together with the voltage from the storage device 13 feeds; cH from the integrator 22, the compensating linear voltage, the slope of which depends of the sum of the residual current at the first survey of the program and the residual current compensation error during the second survey, after the termination of the C5 survey of the program, the voltage proportional to the multiple residual current is summed by torus 15 with compensating with integrator 22 and stored zapominak CIM device 18. When taking the floor all contact management programs Partial axis l1estvl an automatic control circuit 3. At the subsequent deprotection x floor ROGRAMME device operates similarly. A polarograph makes it possible to reduce the slope of the characteristic of the residual cell current by 5–10 times as compared with the known one and, consequently, to increase the sensitivity and accuracy of the determination of microimpurities. In addition, residual current compensation is performed automatically, which significantly increases labor productivity. These advantages make it possible to more intensively introduce the polarographic method into the sphere of production in order to control technological processes, thereby increasing the quality of products and reducing the scrap rate. This is especially true for electronic npONffisiuieHHOCTH, which places high demands on the purity of the materials and solutions used. . i. The invention is an alternating current polarograph containing a phase shifter, linear-varying and alternating voltage generators connected through a potentiostat to an anode cell, to the cathode of which a low-frequency amplifier is sequentially connected, a phase detector, a filter to the output of which is connected to a recorder and a permanent amplifier current, connected via a key to a memory device, characterized in that, in order to increase sensitivity and accuracy, two adders, an integrator, two The device has four keys, and the filter output is connected to the input of the first adder, the output of which is connected via the first and second keys to both additional storage devices, the outputs of which are connected via the third and fourth keys to the integrator input, the output of which is connected to the inputs of the totalizer, and the second input of the second adder is connected to the output of the main memory device, and the output is connected to the input of the phase shifter via a control. Sources of information taken into account during the examination 1. Tsvasman S.B. Electronic floor graphics. Moscow, Metallurgists, 1960 p. 12. 2. USSR author's certificate No. 817577, cl. G 01 N 27/48, 1978 (prototype) ...