JPS62157536A - Signal detection method for spectrophotometer - Google Patents

Abstract

PURPOSE:To achieve a higher property of following hourly changes in the absorbance of a sample, by setting the fetching of signals to a signal processing circuit so that the fetching frequency of sample signals will be higher than those of reference signals and dark signals. CONSTITUTION:A while light from a light source 1 is applied to a beam splitter 3 through a spectroscope 2. One luminous flux separated is transmitted through a sample or made to pass through a storage sample chamber 4A to be incident into a detector 5A while the other luminous flux is made to pass through a reference chamber to be incident into a detector 5B. Signals from the detectors 5A and 5B are fetched alternately into a signal processing circuit 7 through a changeover switch circuit 6. The circuit 6 is controlled in the switching by a synchronous signal P from a sample signal multifrequency fetching synchronous signal generation circuit 10. The signal P activates the circuit 6 to operate to fetch a sample signal S-reference signal R-sample signal S-dark signal D in the order during one cycle. This achieves a higher property of following hourly changes in the absorbance of a sample.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is applicable to the light transmittance or r? of various samples. , concerning spectrophotometers for measuring yield, particularly spectrophotometers that do not perform wavelength scanning, such as spectrophotometers in liquid chromatography, and whose reference signal and dark signal vary slowly relative to changes in the sample signal. The present invention relates to a signal detection method.

2. Description of the Related Art As a conventional spectrophotometer, one shown in FIG. 6, for example, is known. In Fig. 6, white light emitted from a light source 1 is separated into monochromatic light in a predetermined wavelength range by a spectroscope 2, which is separated into two light beams by a beam splitter 3, etc., and one light beam (sample light beam) is separated into two light beams. The beam passes through the sample chamber 4A where the sample passes or is stored and enters the detector 5A such as a photomultiplier tube, and the other beam (reference beam) is almost the same as that of the sample chamber without the sample. The reference beam 4B having an absorption rate is transmitted and made incident on a detector 5B such as a photomultiplier tube. The detection signal of the sample-side detector 5A, that is, the sample signal S that measures the transmitted light intensity of the sample, the detection signal of the reference-side detector 5B, that is, the reference signal R, and the detection signal of the detector in a state where no light is incident on the detector. A dark signal D for zero correction corresponding to the output signal (using the dark signal or a ground level signal when optically considered as a dark signal) is alternately switched by the changeover switch circuit 6 as shown in FIG. The signal is switched and applied to the signal processing circuit 7. In this signal processing circuit 7, the signals S1R and D, which are alternately switched and added by the switch circuit 6, are digitized by the AD converter 8, and the arithmetic processing circuit 9 converts the sample signal S and the reference signal R into a dark signal. and the subtracted signal (S-D), (R-
D), that is, (S-D>/(R-D>). The value of the ratio obtained in this way is calculated by subtracting the dark signal, and the effect of drift and noise in the signal path is calculated. It represents the sample transmittance (the reciprocal of the absorbance) which has been removed and the influence of light source fluctuation has also been removed.

Here, in the conventional general spectrophotometer, the sample signal S is taken into the signal processing circuit 7 by the changeover switch circuit 6.
, the reference signal R, and the dark signal are normally set at equal frequency, one each in one cycle, as shown in FIG.

Problems to be Solved by the Invention Previous) Spectrophotometers such as E have been widely used in high-performance liquid chromatography, but in high-performance liquid chromatography, changes in absorbance over time for light in the same wavelength range are important. It is necessary to obtain it chromatographically, and wavelength scanning is not performed. In order to perform highly accurate chromatographic analysis in such high-speed chromatography, it is necessary to improve the ability to follow changes in sample absorbance over time. It is necessary to shorten the intake interval as much as possible. However, in conventional spectrophotometers, as shown in Figure 7, the sample signal S, reference signal R, and dark signal were captured at equal frequencies, so signal followability was limited by the equal frequency of capture. That is the reality.

This invention was made against the background of the above-mentioned circumstances, and, like the high-performance liquid chromatographic spectrophotometer,
The present invention provides a signal detection method for a spectrophotometer that does not perform wavelength scanning, which improves the ability to follow changes in the absorbance of a sample over time, and enables highly accurate analysis.

Means for Solving the Problems As mentioned above, in high performance liquid chromatography spectrophotometers, wavelength scanning is not performed, but detection is performed in a fixed wavelength range. In this case, fluctuations in the reference signal are much gentler than in the case of wavelength scanning. Also, there are less fluctuations in the reference signal due to fluctuations in the light source and fluctuations in the dark signal due to drift due to temperature changes in the electrical signal path. Therefore, in this case, it can be said that the fluctuations in the reference signal and dark signal are much gentler than the changes in the sample signal due to changes in the absorbance of the sample. This means that in a high-performance liquid chromatography spectrophotometer, even if the frequency of introducing the reference signal and dark signal into the signal processing circuit is reduced, there is little effect on analysis accuracy. Therefore, in the present invention, the frequency at which the sample signal is taken in is made relatively higher than the frequency at which the reference signal and the dark signal are taken in, thereby increasing the ability of the detection data to follow changes in the absorbance of the sample.

Specifically, this invention provides a sample signal corresponding to the intensity of light transmitted through the sample, a reference signal corresponding to the intensity of light transmitted through the reference, and a dark signal corresponding to a state where no light is incident. and the signal processing port alternately.

In a spectrophotometer, the signal processing circuit calculates the ratio between the signal intensity obtained by subtracting the dark signal from the sample signal and the signal intensity obtained by subtracting the dark signal from the reference signal. ￥Ti! is set so that the frequency of sample signal intake within a certain period of time is higher than the frequency of reference signal intake and the frequency of dark signal intake. That is.

Function: In the signal detection method of the present invention, the sample signal is introduced into the signal processing circuit at a higher frequency than the reference signal and the dark signal. Therefore, if the sample signal intake frequency, reference signal intake frequency, and dark signal intake frequency are equal (equal frequency intake)
Compared to this, even if the switching interval of each signal is constant, the sampling interval of the sample signal is shortened, and therefore the ability to follow the change in absorbance of the sample over time becomes better.

On the other hand, the frequency of acquisition of the reference signal and dark signal becomes relatively low, which means that if the switching interval of each signal is constant, the interval of acquisition of the reference signal and dark signal becomes longer. As mentioned above, in high performance liquid chromatography, wavelength scanning is not performed, so the fluctuations in the reference signal are gradual, and the fluctuations in the dark light signal are also small, so even if the acquisition interval is long, the accuracy of the final data is It doesn't really decrease.

Embodiment FIG. 1 shows an example in which the method of the present invention is applied to a spectrophotometer that captures a sample signal S and a reference signal R simultaneously in parallel. In FIG. 1, the same elements as those of the prior art shown in FIG. 6 are designated by the same reference numerals, and their explanation will be omitted.

In FIG. 1, a changeover switch circuit 6 for alternately inputting signals from each detector 5A and 5B to a signal processing circuit 7 is switched by a synchronization signal P from a sample signal frequent input signal generation circuit 10. is controlled. This synchronization signal P
, the changeover switch circuit 6 is connected to the sample signal S-reference signal R-
Sample reliability s-dark signal, 5-R-3-D, 5-R-
The signal is such that the data is operated to be captured in the order of 3-D. FIG. 2 schematically shows the form of the signal taken into the signal processing circuit 7 in this manner.

As can be understood from FIG. 2, if the cycle in which one each of the reference signal R and the dark signal R is taken in is one period below, the sample signal S will be taken in twice during that one period. Therefore, compared to the case of equal frequency acquisition as shown in FIG. The spacing is reduced by 2/3.

Note that the acquisition interval for the reference signal R and the dark signal will be longer, but by making the time constant in the circuit larger than before, the S/N ratio of the dark signal is improved, and then the sample signal is Even if the time constants of the reference signal R and the dark signal are increased in this way, their fluctuations are extremely gradual, so this is not a particular problem. There isn't.

3 and 4 show an example in which the present invention is applied to a spectrophotometer that sequentially detects a sample signal S, a reference signal R, and a dark signal D.

In FIG. 3, the sample light that has passed through the sample 4A passes through the mirror 11, passes through the sector 12, and enters the detector 5, and the reference light that has passed through the reference 5B passes through the mirror 13 and is reflected by the sector 12. and incident on the same detector 5. Here, the sectors 12 divide the disk at 90' intervals as shown in FIG.
A, the reference light reflecting section 12B, and the second sample light transmitting section 12
C and transmit the sample light 1! A non-reflective portion 12D that substantially does not reflect even reference light is formed in this order.

By rotating such a sector 12 around its axis O by a rotation drive source 14 such as a motor, the detector 5 receives sample light, reference light, sample light, and the influence of the surroundings in one rotation of the sector 12. bright light (dark light) is incident in that order. Therefore, the detector 5 directly outputs a 5-R-3-D signal as shown in FIG.

In this case, since the output of the detector 5 itself becomes a sequential signal with a high frequency of sample signals, the changeover switch circuit 6 as in the case of FIG. 1 can be omitted.

Note that when the changeover switch circuit 6 is used to input a signal into the signal processing circuit 7 as shown in FIG. You may also incorporate FIG. 5 shows the acquisition to the signal processing circuit 7 when other signals P are surrounded during the dark signal period.

The actual construction of the signal processing circuit 7 is of course not limited to the example shown in FIG. 1, and it goes without saying that a personal computer may be used as the arithmetic processing circuit.

It goes without saying that similar processing can be performed in the case of a multi-wavelength spectrophotometer that simultaneously detects multiple wavelengths using a multi-element detector such as a diode array.

Effects of the Invention As is clear from the above explanation, according to the signal detection method of the present invention, when the reference signal and the dark signal fluctuate slowly, such as in a high-performance liquid chromatography spectrophotometer, the sample signal acquisition interval can be reduced. By shortening the length of time, it is possible to improve the ability to follow the change in absorbance of the sample over time, thereby improving the analytical accuracy compared to the conventional method.

[Brief explanation of drawings]

1 is a block diagram showing an example of a spectrophotometer used in carrying out the method of the present invention; FIG. 2 is a diagram showing an example of a signal waveform introduced into a signal processing circuit in the method of the present invention; FIG. 3 is a block diagram showing another example of a spectrophotometer used to carry out one method of the present invention, FIG. 4 is a plan view showing sectors in the spectral beam 1 of FIG. 3, and FIG. 5 6 is a diagram showing another example of the signal waveform incorporated into the signal processing circuit in the method of the present invention, FIG. 6 is a bronze diagram showing an example of a conventional spectrophotometer, and FIG. 7 is a diagram showing a conventional spectrophotometer. FIG. 2 is a diagram showing an example of a signal waveform in FIG. R... Reference signal, S... Sample signal, D... Dark signal, 4A... To sample, 4B... To reference,
5.5A, 5B...detector, 6...changeover switch circuit, 7...signal processing circuit, 12...sector.

Claims (2)

[Claims] (1) Signal processing alternately with a sample signal corresponding to the intensity of light transmitted through the sample chamber, a reference signal corresponding to the intensity of light transmitted through the reference chamber, and a dark signal corresponding to the state where no light is incident. In a spectrophotometer, the signal processing circuit calculates the ratio between the signal intensity obtained by subtracting the dark signal from the sample signal and the signal intensity obtained by subtracting the dark signal from the reference signal. A method for detecting a signal in a spectrophotometer, characterized in that the frequency of sample signal is set to be higher than the frequency of reference signal and dark signal within a certain period of time. (2) One reference signal and one dark signal in the signal processing circuit
2. The signal detection method in a spectrophotometer according to claim 1, wherein the sample signal is taken in twice during one cycle in which the sample signal is taken in twice.