SU911300A1 - Method of ac polarographic analysis - Google Patents

Description

(54) METHOD OF YEREMENO CURRENT POLEUGRAFIC ANALYSIS

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The invention relates to chemical and chemical research and can be used for the qualitative and quantitative analysis of solutions.

Methods for alternating polarographic analysis are known, according to which, at the same time as a constant, linearly time-varying voltage, a small-sized alternating voltage of different form 1 is applied to the polarographic cell.

However, these methods do not allow Reaching the maximum possible sensitivity, since informative is only a part of the measured signal corresponding to the value of the active cell current. In addition, the exclusion of the current signal due to the useful reactive component of the Faraday resistance of the polarographic cell from the measured signal does not allow to increase the sensitivity by increasing the frequency of the alternating polarizing voltage.

The closest to the proposed technical essence is the method of alternating polarographic analysis, which consists in the fact that a constant linearly varying voltage and an alternating sinusoidal voltage are simultaneously applied to the polarographic cell, the active component of the alternating voltage is measured and measured. cell current 2.

The disadvantage of this method is 10 seconds in relatively low sensitivity.

The purpose of the invention is to increase the sensitivity of the assay.

Claims (2)

The goal is achieved by the fact that in the well-known method of alternating polarographic analysis, which, when determining the co-concentration of the components of the analyzed solution, a constant linearly varying voltage and alternating sinusoidal voltage are simultaneously applied to the polarographic cell, the component of the alternating current cell, additionally allocate a signal proportional to the modulus of the reactive composition of the 3. alternating current cell, subtract from it the magnitude of the signal of the active component current, the resulting signal is used to compensate the capacitive current dual layer Nogo measuring electrode and the concentration of the solution components is determined by the magnitude of the total current floor rograficheskoy cell. The reactive component of the ac current of the polarographic cell is equal to the sum of the currents due to the capacitance of the double layer of the measuring electrode and the useful Faraday capacitance (pseudo-capacity). At the same time, the reactive component of the Faraday resistance due to pseudocapacity is equal in modulus to the active component, provided that the 1A reaction on the electrode is reversible. Thus, by highlighting the reactive component of the cell full current and OS} W (in order to quantify the active component, a signal is obtained that is equal to the reactive cocTajB of the current current cell, due only to the capacitance of the double layer of the measuring elec. Type. the sensation of the mixing reactive current, and the concentration of the corresponding components of the ions in the test solution are determined by the magnitude of the full Faraday current of the polarographic cell. The drawing shows a block diagram of the ocjmjecT and the proposed method. To the polarographic cell 1 from generators 2 and 3, a constant linearly varying voltage and a variable sinusoidal voltage of small amplitude are supplied through the measuring resistor 4. A signal proportional to the total current of the polarographic signal is extracted from the measuring resistor 4 cells 1, which are then amplified by an amplifier 5. At the output of synchronous detectors 6 and 7, connected to the output of amplifier 5 and controlled by quadrature signals, an alternating voltage generator 3 is obtained from This voltage is proportional to the active and reactive components of cell 1 current. Using the computing unit 8, the voltage proportional to the cell's reactive current is subtracted from the voltage proportional to the active component of the current, and the resulting signal to the compensating block 9, which For example, in the form of a voltage controlled electric equivalent of negative capacitance. At the same time, the transmission coefficient of the computational unit 8 is chosen so that the value of the negative capacitance of unit 9, connected in parallel with the polarographic cell 1, is equal to the modulus of the capacitance of the double layer of the measuring electrode. Since the indicated capacitances are equal in magnitude and are opposite in sign, the reactive component of the alternating current cell, due to the capacity of the double layer, will tend to zero. The concentration of the corresponding components in the test solution is determined by the voltage at the output of the amplitude detector 10 connected to the output of the amplifier 5. The value of the measured voltage is proportional to the total current of the polarographic cell due to the Faraday capacitance and resistance. Thus, the proposed alternating method of polarographic analysis allows us to achieve the highest possible sensitivity, since it provides the measurement of H® full-cycle Faraday cell current. Frequency limited above by frequency properties of used measuring units. Formula of alternating polarographic analysis consisting in the fact that, when determining the concentration of the components of the analyzed solution, a constant linearly varying voltage and an alternating sinusoidal voltage are simultaneously applied to the polarographic cell, the active component of the alternating current cell, characterized in that , in order to increase the sensitivity, additionally allocate a signal proportional to the reactive component module of the alternating current cell; well active current component signal, the resulting signal is used to compensate the double layer capacitive current measuring electrode, and the concentration of the solution components is determined by the magnitude of the total current floor rograficheskoy cell. Sources of information taken into account during the examination 1. Tsfasman S. B. Electron polografy. M., Metallurgizdat, 1960, p. 109. 2. The same, with 121 spototype).