JPS61155731A - Photometric signal processing circuit for chromatoscanner - Google Patents

Abstract

PURPOSE:To prevent sharp changes in the sensitivity of a photometry system, by providing a sample holding circuit in dynode feedback path from a photo multiplier for monitoring to hold a detection signal even immediately after luminous flux incident into a sample plate is interrupted. CONSTITUTION:The interruption of luminous flux passing through a crossing section between a rectangular slit and a slit of a slit disc is detected by a timing detection means 54 immediately therebefore and the current input voltage is held into a sample holding circuit 32. During the interruption of the luminous flux from the rectangular slit, a dynode feed backing is applied to photo multiplier tubes 14, 22 and 24 based on the voltage level held in the sample holding circuit 32. The crossing between the rectangular skit and the slit of the slit disc is restarted, when the luminous flux irradiates a sample plate again, the sample holding circuit 32 is turned OFF by a signal from a timing detection circuit 54 to change the measuring path to the normal one.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a chromato scanner used for optically quantifying sample fractions separated on a sample plate in thin layer chromatography, etc. The present invention relates to a photometric signal processing circuit in a so-called flying spot type chromatographic scanner that scans a minute beam of light irradiated onto the surface.

(Prior art) To configure a flying spot chromatography scanner that performs measurements by moving a minute beam of light irradiated onto a sample plate, the beam imaging mirror is swung left and right around a rotation axis. It was necessary to make a reciprocating movement by swinging the slit from side to side, or by swinging the slit inscribed with the shape of the minute beam of light to be imaged. Especially if you aim to go faster.

In the method of shaking the mirror (or rotating it only in one direction), the upper limit of the speed is determined by the inertial load of the mirror, and in the method of making the slit reciprocate, a motor (generally a step motor is often used) is used. ) requires frequent forward and reverse rotations, which impedes continuous high-speed operation of the motor (the same applies when shaking the mirror left and right).
This was preventing the speeding up of chromatographic scanners.

(Problem to be Solved by the Invention) Therefore, the present inventors rotated a slit disk in which elongated slots or slits of a specific pattern were punched into the disk, and combined it with ordinary elongated rectangular slits. We have separately proposed a flying spot type chromatographic scanner that scans the irradiation beam onto a sample plate by passing light through a hole at the intersection of the two.

The flying type chromatographic scanner is schematically shown in FIG. 4. Reference numeral 2 denotes a rotary slit disk, and slits 4-1 and 4-2 whose distance from the center changes according to the rotation angle are provided. This slit disk 2 is attached to the rotating shaft of a motor 8.

The motor 8 is preferably a step motor.

A rectangular slit 10 is combined with the slit disk 2, and both are positioned so that the longitudinal direction of the rectangular slit 10 is in the radial direction of the slit disk 2. The rectangular slit lo may be the exit slit of a spectroscope (not shown). The slit 4-1 or 4- of the zero-rotation slit disk 2
2 and the rectangular slit 10, monochromatic light from the spectroscope passes through the hole.

12 is a half mirror, and the slit 4 of the slit disk 2
1 or 4-2 and the rectangular slit 1o is guided to the photomultiplier tube 14 for monitoring, and the remaining part is directed to the sample plate 20 through the optical element 16-18 for imaging. The sample plate 20 to be guided is supported by a stage (not shown) so as to be movable in the X direction and the Y direction.

22 is a photomultiplier tube that detects reflected light from the sample plate 20, and 24 is a photomultiplier tube that detects transmitted light from the sample plate 2o.

Fig. 5 shows the slit disk 2 in detail, slit 4-1.
．． 4-2 is formed in a spiral shape so that the distance from the center increases from R+ to R2 as the slit disk 2 rotates in the direction of the arrow.

The rectangular slit lO is connected to the slit 4-1 of the slit disk 2.
．． When scanning while sequentially crossing each other according to 4-2,
While the irradiation light flux moves to another scanning line or lane on the sample plate, that is, during the period when the range of θl and 02 intersects the rectangular slit 10 in FIG. 5, the light flux passing through the slit disk 2 disappears. Therefore, if the photomultiplier tube 14 for light source monitoring and the photomultiplier tubes 22 and 24 for photometry are used with dynode feedback, the supplied negative high pressure will suddenly rise for a moment, and the sensitivity will become unstable. is broken. To improve the scanning speed of the chromato scanner, the slit disk 2 is rotated at high speed for measurement, but the response of the photometric signal processing system can only follow up to a certain speed.
If the negative high pressure level suddenly rises, the measurement will be performed at the changed level, that is, the photometric sensitivity will be changed, and correct measurement will not be performed.

In addition, the sample plate 2 is also attached to the photomultiplier tubes 22 and 24 for photometry.
Since light from 0 no longer comes, if the photometric signal passes through the preamplifier and the logarithmic conversion amplifier in sequence, the output will be saturated when the final output is obtained as an absorbance signal. This is because the input of the logarithmic conversion amplifier becomes 0.

It is necessary to configure a photometric electrical system that prevents these abnormalities from occurring and always operates stably and accurately.

The present invention allows the photocurrent from the monitoring photomultiplier tube, which disappears during a temporary interruption of the light flux leaking from the exit slit of the spectrometer, to remain apparently, thereby creating a breakthrough negative high voltage via dynode feedback. It is an object of the present invention to provide a photometric signal processing circuit that does not cause an increase.

(Means for Solving the Problems) The photometric signal processing circuit according to the present invention will be explained with reference to FIG. The sample hold circuit 32
Timing detection means 54 is provided to control the operation of the .

(Function) Rectangular slit 10 and slit 4-1 of slit disk 2
Alternatively, the timing detection means 54 detects the moment immediately before the light beam passing through the intersection with 4-2 is interrupted, and the sample-hold circuit 32 holds the input voltage at that time. During the interruption period of the light flux from the rectangular slit 1O, dynode feedback is applied to the photomultiplier tubes 14, 22, and 24 based on the voltage level held in the sample and hold circuit 32.

When the intersection between the rectangular slit 10 and the slit 4-1 or 4-2 starts again and the sample plate 20 is irradiated with the light beam again, the sample hold circuit 32 is turned off by a signal from the timing detection circuit 54 and the normal operation is performed. Switch to the photometry path.

(Example) FIG. 1 is a circuit diagram showing one embodiment.

14, 22, and 24 are photomultiplier tubes for monitoring 1 for detecting reflected light and for detecting transmitted light, respectively, shown in FIG. 30 is a preamplifier (preamplifier) that amplifies the detection output of the monitor photomultiplier tube 14; 32 is a preamplifier 30;
A sample-and-hold circuit 34 inputs the output voltage of the sample-and-hold circuit 32 to the photomultiplier tube 14.
Convert to negative high pressure of 22°24 and apply each photomultiplier tube 14°2
This is a DC-DC converter for dynode feedback that applies negative high voltage to 2.24.

36 is a preamplifier that amplifies the detection output of the photomultiplier tube 22 for detecting reflected light, and 38 is a photomultiplier tube 24 for detecting transmitted light.
This is a preamplifier that amplifies the detection output of the preamplifier 3.
Sample and hold circuits 40 and 42 are connected to the output terminals 6 and 38, respectively. Logarithmic conversion amplifiers 44°46.48 are connected to the output terminals of the sample and hold circuits 32 and 40°42, respectively, and the output terminal of the logarithmic conversion amplifier 44 is connected to one input terminal of the absorbance signal amplifier 50. The output terminals of the conversion amplifiers 46 and 48 are connected to the absorbance signal amplifier 5 via the changeover switch SWI.
0 is connected to the other input terminal of 0.

The output terminal of the absorbance signal amplifier 50 is a changeover switch SW.
2 to the A/D converter 52. The A/D converter 52 is also connected to an output terminal of a preamplifier 36 for detecting reflected light via a changeover switch SW2.
This path connected from the preamplifier 36 for reflected light detection to the A/D converter 52 is a path for fluorescence measurement. A
The /D converter 52 converts the absorbance signal from the absorbance signal amplifier 50 or the fluorescence signal from the preamplifier 36 into a digital signal and sends it to C:PU (as shown).

A negative high voltage is applied to the photomultiplier tube 24 for detecting transmitted light through a switch SW3 so that it is activated only when the sample plate is of a transmission type.

A timing detection means 54 is connected to the sample and hold circuits 32, 40, and 42. Timing detection means 5
4 is realized by the CPU, and by detecting the number of pulses or time from the rotation start point of the motor 8 (for example, a step motor) that drives the slit disk 2 as shown in FIG. Slit 10 and slit 4-
The timing at which the crossover with 1 or 4-2 starts, the timing at which the crossover ends, etc. are detected.

FIG. 2 specifically shows an example of the sample and hold circuit 32, 40° 42. The signal from the preamplifier 30° 36 or 38 is sent to the operational amplifier via one input terminal of the sample-side analog switch 60 and the hold-side analog switch 62. (operational amplifier) 64. A time constant circuit consisting of a series resistor Rr and a parallel capacitor C is connected between one input terminal of the analog switch 60 and the analog switch 62. The resistor R+ is provided for adjusting a time constant to enable high-speed photometry during normal photometry. The switching operation of the analog switches 60 and 62 is performed by control pulses generated from the timing detection means 54. A resistor R2 connected between one input terminal and the output terminal of the operational amplifier 64 is for converting photocurrent input into voltage output.

Here, the operation of this embodiment using the sample and hold circuit shown in FIG. 2 will be explained.

During normal photometry, that is, when the sample plate is irradiated with a light beam, the analog switch 60 is turned on and the analog switch 62 is connected to the upper terminal in the figure, so that the light beam incident on the sample plate is interrupted. Immediately before, the sample-side analog switch 60 is turned off while the photometric signal at the final point of the scanning stroke of the rectangular slit section is sampled.

While the incident light flux is interrupted, the hold-side analog switch 62 is connected to the lower terminal connected to the capacitor C, and the input voltage is held.

Next, at the point when the incident light beam starts to enter each photomultiplier tube 14, 22, 24 again (immediately after the incident light beam enters), the analog switch 62 is switched to the upper side in the figure again, and then the analog switch 62 is switched to the upper side in the figure. Turn it back on again to return to normal photometry mode.

In this embodiment, the sample and hold circuits 40 and 42 are also installed where the signal from the photomultiplier tube 22 and 24 for m light comes.
, so that the optical signal on the side appears to exist even during the period when the incident light flux to the sample plate is interrupted, so that the final The absorbance signal obtained in this way also becomes unsaturated.

As a modification of this embodiment, the sample and hold circuit 32.4
2 can be provided between the input terminal of the preamplifier 30, 38 and the photomultiplier tubes 14, 24, respectively.

In addition, the preamplifier 30.38 is the sample hold circuit 3.
The operational amplifier 64 in 2.42 may also be used.

FIG. 3 specifically shows another example of the sample-and-hold circuit 32, 40° 42. Preamplifier 30.36
Or the signal from 38 is the hold side analog switch 62
The signal is input to the operational amplifier 64 through one input terminal of the .

The other input terminal of the hold-side analog switch 62,
A hold capacitor C connected between the input terminal connected to the preamplifier 30, 36 or 38 is connected to the input terminal connected to the preamplifier via the sample side analog switch 66. The analog switches 66 and 62 perform switching operations in response to control pulses from the timing detection means 54.

In this sample hold circuit, during normal photometry, the switch 66 is turned off, and the switch 62 is connected to the upper side in the figure.
Immediately before the incident light beam on the sample plate is interrupted, the switch 66 is turned on to cause the capacitor C to hold the input voltage. During interruption of the incident light flux, the switch 66 is turned off, the switch 62 is connected to the lower side in the figure, and the maintained voltage causes dynode feedback to the photomultiplier tubes 14, 22, 24, etc. When the rectangular slit and the slit of the slit disk intersect again, the switch 62 is activated.
1. Switch to the upper side of the diagram to return to the normal photometry state.

As another modification of the present invention, the number of slits in the slit disk is an even number, and slits of different groove widths are cut out alternately, so that only one of the two types of slits is used during actual measurement to obtain absorbance data. The rectangular slit may be read and recorded on the recorder, or the rectangular slit may be replaced with one with a different banner, or the scanning stroke may be changed by changing the height of the rectangular slit. Instead of switching, this may be done by changing the data reading section in the scanning direction using the computer inside the device. With this modification, it is possible to freely set the size of the irradiation point on the sample plate and the scanning stroke. Become.

(Effects of the Invention) In the present invention, a sample hold circuit is provided in the dynode feedback path from the monitoring photomultiplier tube, so that even when the light beam incident on the sample plate is interrupted, the detection signal immediately before the interruption is held. This prevents sudden increases in negative high voltage applied to the photomultiplier tube, which would otherwise occur without a sample hold circuit, and prevents sudden changes in the sensitivity of the photometry system, making it possible to perform stable and accurate measurements. It becomes like this.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment, FIGS. 2 and 3 are circuit diagrams each showing an example of a sample hold circuit used in the embodiment, and FIG. 4 is a circuit diagram of a chromatography scanner in which the present invention is used. FIG. 5 is a schematic perspective view showing an example of the optical system, and FIG. 5 is a plan view showing the slit disk in FIG. 4. 2...Slit disk, 4-1.4-2...
...Slit, 10...Rectangular slit, 14,22゜24...Photomultiplier tube,
20...Sample plate, 32.40.42.
... Sample hold circuit, 34 ... DC-DC converter for dynode feedback, 5
4... Timing detection means.

Claims (2)

[Claims] (1) In the photometric signal processing circuit of a flying spot chromatographic scanner that intermittently irradiates and scans a sample plate with a beam of light and performs detection with a photomultiplier tube, the sample hold circuit at least connects the photomultiplier tube for monitoring. The photometric signal is provided in a dynode feedback path from the dynode feedback path, and further includes timing detection means for detecting the timing of intermittent irradiation of the sample plate and controlling the operation of the sample hold circuit. processing circuit. (2) The photometric signal processing circuit according to claim 1, wherein a sample hold circuit controlled by the timing detection means is also provided at an input section to the logarithmic conversion amplifier.