SU761903A1 - Chromatographic peak detecting system - Google Patents

Description

The invention relates to gas analysis and can be applied in gas chromatography to detect the peaks of certain components, for example, 'pe- st' 'cids. '

A known system for detecting chromatic pictographs, installed in a gas analyzer, is designed for obia; I'm sure I have specific vapors in the air. When detected in the gas chromatographic spectrum of peaks / target components, the system generates an alarm signal [1].

Also known is a detection system of chromatographic peaks containing a sequentially installed detector with a stabilized source of supply voltage, an electrometric amplifier with a differential input connected by an inverted input to the collecting electrode of the detector / peak detection circuit at specified time intervals and an indication unit [2]. / / - <

However, sometimes during the analysis, a chromatographic peak of the substance E is emitted with a high concentration, causing a signal that exceeds the amplitude of the dynamic range of the electric amplifier (the effect of a zoomer) to the detector. This is typical of 'search gas analyzers, since the concentrations of the sought after ones are' ’* ·· -, · .'- ·. ·

/ 2, '. ,

They are unknown beforehand, and in order to avoid skipping, the device most often turns on for maximum sensitivity. But izvestpaya sistema'ie ^l capable identi ⁵ feast a peak and • it may miss or false trigger signal trovogi. The aim of the invention is higher 'reliability of detection: peaks desired material while extension ⁰ NII dynamic range of the system.

This goal is achieved by the fact that

system introduced voltage comparator, down counter, a digital to analog pre 'the forming controlled valve gene ⁵ Rhatore clock and shaper' time slots, wherein one comparator input 'connected to' the output of an electrometric amplifier, the second input - to the "zero", and the output - councils to inputs ^0, pull a down counter,

. the output of the counter is connected to the input of the digitizer, - the output of the “last” is connected to the second non-authenticated “input” of the differential electrometric amplifier, and the clock input of the reversing counter is connected to the clock input of the reverse clock; tracking a zero electromotive amplifier, “about the second:

761903

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The gate input is connected to a circuit for determining the peaks of a time interval generator clocked by the generator, which prohibits the passage of pulses to the "clock" ⁵ input of the reversible counter for these periods of time and allows the peaks determination circuit to be operated at the same time intervals.

In the chromatography detection system, the electrometer does not amplify the 10 peaks. The absolute value of the measured value is · "

"the difference between the current value at the time of the termination of tracking zero and adding it to 'during the working period. ⁴ _ - 15

Since the "clearing" occurs non-.

'long before the appearance of the vertex * prspdopola; _x Ai peaks, amplifies the measured current increment easily fit into the dynamic measuring dyapazon 20 Cu tem. · ,, .... · · · ,.

When the Detector current is compensated by the voltage on the measured inverted input, the electrometric amplifier changes in proportion to the measured value, 25 and the operating point of the current-voltage characteristic of the detector is shifted accordingly. The displacement of the working point of the detector from the optimum causes a decrease in The sensitivity of the detector, which especially affects the “uncoupling” of the system, due to the peak of the peak with a high concentration of the component. H

^l In FIG. 1 shows a functional diagram of the proposed system; in fig; 35 2 a, b Comparative illustration of the detector signals arriving at the input of the peak detection circuit. '/

The system for detecting chromatographic peaks contains a detector 1 electron- “adiabatic capture with a source-2 of a stabilized supply voltage, electr ⁴ differential amplifier 3 with input, 4 peak detection circuit at given time intervals, 45 torr picdv 5, comparator 6, reversible counter 7, digital-to-analog converter 5, valve 9, 10 clock pulse generator, shaper 11 time intervals. , 50

The system works as follows.

Comparator 6 determines the deviation from the "zero level and. Sign of the deviation of the signal of the detector 1 at the output of the electrometric amplifier 3, thereby setting 55 the counting direction of the reversible counter 7. The latter accumulates a number proportional to the voltage at the output of the electrometric amplifier 3. The digital-to-analog converter 8 converts the accumulation-θθ The number recorded on the counter 7 is in the analog signal and feeds it to the non-inverted input of the electrometric amplifier.3 to compensate for the measured current / й yddTo "zero" at the input of the amplifier 3. The rate of Tell θ5

four

tracking the zero of the electrometric ubilitel 3 is determined by the frequency of the clock generator 10, the pulses from which through the valve 9 are fed to the clock input of the reversible counter 7.

The shaper of 11 time intervals, clocked by generator 10, sets the time periods during which the '4 peak detection scheme is engaged in their search, and prohibits for this time πρόхWAHING clock pulses to the input of the counter 7 at the second input of the gate 9.' ,

Pulse counter 7 stores the number,. the calculated voltage on it, respectively, also keeps the compensating voltage, on the noninverted input of the differential electro- metric amplifier 3 in the current of this collection and processing time interval.

Comparative recordings of chromatograms (Fig. 2'a, b) illustrate the work of the known and proposed systems. During the time intervals τ — τ _{4, the} electrometer “raznulyaetsya” and the signal enters the scheme for determining peaks. In contrast to the known system (Fig. 2 a), the peak amplitude in the interval is in the dynamic range of the output signal of the electrometric amplifier (Fig. 2-6). ,

Was the proposed system manufactured and tested? in a gas chromatographic device for determining the level of air pollution by pesticides.

. Test results showed high operational reliability of the system, ensuring the detection of peaks in a wide range of _ changes ~ input .. concentrations of detectable components. ' The effective dynamic range of detection has increased to 4 · 10 ³ —6 · 10 ³ of the level, the statistical noise of the detector, comprising 2 - 10 - 13A,

The system saved important _h servation designed to observe peaks linear characteristics of the amplifier: Logarithmic amplifiers largely smooth embossing chromatographic spectrum and complicate subsequent 'operation on the identification and detection of peaks. In addition, the high stability of maintaining the memorized level of the “zero” signal is ensured, which is of interest for chromatographic instrumentation.

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Claims (1)

Claim ν _: Chromatographic detection system. peaks, containing sequentially mounted detector with a stabilized power supply source, an electrometric amplifier with a differential input, connected by an inverted input to the collecting electrode of the detector, a scheme for determining peaks in given time intervals and a display unit, 7619 () 3 characterized in that, in order to increase the reliability of detecting the peaks of the desired substances while simultaneously expanding the dynamic range of the system, a voltage comparator, a reversible counter, a digital-to-analog converter, a controlled valve are introduced into it; clock generator and shaper time intervals, and. one input of the comparator / connected to the output of the electrometric amplifier, the second input to “zero”, and the outputs to the controlled, reversible counter inputs, the output of the counter connected to the input of the digital-analog converter, the output of the last connecting chen to the second converted input of the differential electrometric "of the amplifier, the clock pulse generator is connected to the contact input of the relay counter, a clock generator of a time inverter connected by the generator is connected to the second gate input and to the peak detection circuit. 1 °