JPH0249645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a photometer, and particularly to a photometer suitable for simultaneously performing fluorescence measurement and absorption measurement for qualitative and quantitative analysis.

[Background of the invention]

Conventionally, as shown in Japanese Unexamined Patent Publication No. 174833/1983, a fluorometer has been proposed that is provided with both a transmitted light measurement channel and a fluorescence measurement channel. However, the main purpose of this is to correct the fluorescence signal using the transmitted light signal, and there are many problems when measuring transmitted light itself as a measurement target. In other words, high-intensity lamps that can be used for fluorescence measurements, as typified by xenon lamps, have irregular fluctuations that cannot be grasped statistically (non-
stationary fluctuations), and irregular noise is superimposed on the photometric values. Therefore, unless the sample concentration is particularly high, the variation value due to the light source variation becomes larger than the difference in level between the blank transmitted light and the sample transmitted light, making measurement impossible. That is, when the blank transmitted light intensity is I ₀ and the sample transmitted light intensity is I, the absorbance A is expressed as A=-logI/I ₀ (1), and in a xenon lamp etc., I,
There is a variation of about ±3% in each I ₀ , and the uncertainty of I/I ₀ is about 6%. As a result, noise of about 0.03 is superimposed on the absorbance A. In particular, the sample concentration is low and the optical path length is short, making it unusable as an absorption photometer for liquid chromatography.

In addition, such light source fluctuations often cause
It is a non-stationary fluctuation, the frequency components etc. are uncertain, and it cannot be treated statistically. In the worst case, it may not show any form of noise, but may show unidirectional movement, such as a step in the signal level. Therefore, it is difficult to smooth the signal in a signal processing system.

On the other hand, as a way to avoid the above fluctuations,
Using a deuterium lamp with excellent stability seems to be an effective method, but in the wavelength range of 270 to 400 nm, which is frequently used in fluorescence intensity measurements, the brightness is 1 to 2 orders of magnitude lower than that of a xenon lamp. Since the sensitivity in fluorescence intensity measurement is proportional to the excitation light intensity, this is a fatal drawback in fluorescence intensity measurement.

[Purpose of the invention]

The present invention has been made in view of the above, and its purpose is to be able to perform absorbance measurement and fluorescence intensity measurement, and to be able to perform absorbance measurement of low concentration samples and fluorescence intensity measurement of extremely low concentration samples. The object of the present invention is to provide a photometer that can perform measurements with high precision.

[Summary of the invention]

The present invention was made based on the fact that metal halide lamps generally have high brightness and excellent stability, and in particular, tantalum iodide metal halide lamps containing tantalum iodide and mercury exhibit high brightness and high stability in the ultraviolet region. It uses a metal halide lamp as a light source, and its detection system consists of a transmitted light measurement channel and a fluorescence measurement channel.

[Embodiments of the invention]

This will be explained in detail using the embodiment shown in FIG. 1 and FIGS. 2 to 7.

FIG. 1 is a configuration explanatory diagram showing an embodiment of the photometer of the present invention. In FIG. 1, 1 is a lamp power source, and 2 is a tantalum iodide metal halide lamp that is lit by the lamp power source 1. In FIG.

The metal halide lamp 2 will be explained below before explaining the configuration shown in FIG. Figure 2 is a diagram showing a comparison between the brightness of a tantalum iodide metal halide lamp and the brightness of a xenon lamp used in a normal spectrofluorometer. There is. If the brightness of a xenon lamp at each wavelength is normalized to 1, the corresponding brightness of a metal halide lamp will be as shown in the figure.The brightness of a metal halide lamp in the ultraviolet region is not inferior to that of a xenon lamp, and is sufficient for fluorescence measurements. It turns out that it can be used. In addition, Figure 2 shows the bandwidth
These are the results measured using 10 nm spectrophotometry.

FIGS. 3 and 4 are explanatory diagrams of the arc shapes of a xenon lamp and a metal halide lamp, respectively. In FIG. 3, 31 is an anode, 32 is a cathode,
33 is the arc, the arc 33 of the xenon lamp
has a size of about 2 x 1.5 mm, but the highest brightness part 34 is near the cathode 32 and has a diameter of 0.5 mm.
It has a microscopic shape of less than mm. In a xenon lamp, as the partial impedance at the tip of the cathode 32 changes every moment, the position of the highest brightness part 34 changes every moment, and when passed through a spectrometer, the image of the light source moves on the slit. As a result, the light intensity level after passing through the spectrometer is unstable and cannot be used for absorption measurements.

On the other hand, the metal halide lamp (tantalum iodide) shown in FIG. 4 has an anode 41 and a cathode 42.
The arc 43 generated during this period is as long as 10×1 mm, and its shape and position do not change much. This means that it is highly stable even when passed through a spectrometer and can be used for absorption measurements. However, in order to effectively use the light from such an elongated light emitter, consideration must be given to the installation of each optical element.

FIG. 5 is a diagram showing the frequency characteristics of noise (relative values) based on slight variations in the amount of light observed when light from a metal halide lamp is passed through a spectrometer. As shown in FIG. 5, there are many high frequency components, and noise below 1 Hz can be ignored. Therefore,
A damping circuit of 1Hz or more is installed in the signal processing system,
It can be seen that by smoothing high frequency noise, stability is improved and absorption measurement of samples with low absorbance becomes possible. This point is in contrast to the fact that the luminance fluctuations of xenon lamps are non-stationary fluctuations that are difficult to understand statistically, and that damping circuits have little effect.

Next, FIG. 1 will be explained again. The metal halide lamp 2 is turned on, and light emitted from a vertically long arc 3 is focused by lenses 4 and 5 and enters the spectrometer through the entrance slit 6 of the excitation side spectrometer. The light from the input slit 6 that has been dispersed by the diffraction grating 7 passes through the mirror 8, the output slit 9, and the mirror 10, and is focused by the lens 11 and enters the micro flow cell 12. The transmitted light that has passed through the sample in the micro flow cell 12 is focused by the lens 13 and enters the transmitted light measurement detector 20 of the transmitted light measurement channel. On the other hand, micro flow cell 1
The fluorescence emitted by the sample in the spectrometer 2 is focused by the lens 14, passes through the mirror 15, and enters the spectrometer through the entrance slit 16 of the fluorescence side spectrometer. after that,
The light dispersed by the diffraction grating 17 exits from the exit slit 18 and is detected by the fluorescence measurement detector 19 of the fluorescence measurement channel.

Note that the metal halide lamp 2 is installed so that the longitudinal direction of the arc 3 is vertical, and accordingly, the entrance slit 6, the exit slit 9, the flow path in the micro flow cell 12, that is, the part where the sample is measured, The entrance slit 16 and the exit slit 18 are all elongated in the vertical direction.
An image of the arc 3 is formed on the optical element after the entrance slit 6. With these, the light emitted from the arc 3 of the metal halide lamp 2 can be utilized to the fullest.

The output signal of the fluorescence measurement detector 19 is transmitted to the amplifier 2.
1 and recorded on a chart by the recording device 25.

On the other hand, the output signal of the transmitted light measurement detector 20 is
After being amplified by the amplifier 22, the LOG converter 2
3, and after high frequency noise is removed by a damping circuit 24, the signal is recorded on a chart by a recording device 25. Note that by providing the damping circuit 24, it was possible to reduce the noise caused by fluctuations in the light source to a level equivalent to absorbance of 1×10 ⁻⁴ or less.

Figure 6 is a diagram showing the temporal change in the output signal when the metal halide lamp 2 in Figure 1 is replaced with a xenon lamp, the damping circuit 24 is not provided, and the time constant is set to approximately 0.3 seconds. In this case, non-stationary noise appears, and even if a damping circuit is provided, no great effect can be expected. On the other hand, FIG. 7 is a diagram showing temporal changes in the output signal in the case of the configuration shown in FIG. 1 according to the present invention. In this case, there is no noise observed after 3 minutes after lighting. do not.

According to the embodiments of the present invention described above, it is possible to measure absorbance and fluorescence intensity with one photometer, and moreover, it is possible to measure weak fluorescence intensity and to measure the absorbance of a sample with low absorbance. That is, the individual functions can be made comparable to those of a device exclusively for fluorescence measurement and a device exclusively for absorbance measurement. This is effective in the general analysis field, and is particularly effective when applied to a liquid chromatograph photometer where the sample concentration is low and the optical path length of the sample cell is short. In the field of liquid chromatography, both absorbance measurement and fluorescence intensity measurement are considered important, and it is usually difficult to install two photometers above or around the liquid chromatograph body, so this book The photometer according to the invention is optimal. In addition, when an absorption photometer and a fluorophotometer are connected in series and used as a detection system in a liquid chromatograph to simultaneously detect absorbance and fluorescence intensity, the separation in the chromatograph output from the rear photometer is However, if both absorbance and fluorescence intensity are measured by one photometer according to the present invention, poor separation will not occur.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to perform absorbance measurement and fluorescence intensity measurement, and moreover, it is possible to perform absorbance measurement of a low concentration sample and fluorescence intensity measurement of an extremely low concentration sample with high accuracy. There is an effect.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an embodiment of the photometer of the present invention, FIG. 2 is a diagram showing a comparison between the brightness of a tantalum iodide metal halide lamp and the brightness of a xenon lamp, and FIGS. 3 and 4 are explanatory diagrams of the arc shapes of xenon lamps and metal halide lamps, respectively. Figure 5 is a diagram showing the frequency characteristics of noise based on light intensity fluctuations of metal halide lamps. Figure 6 is the output signal when a xenon lamp is used as a light source. FIG. 7 is a diagram showing temporal changes in the output signal of the photometer according to the present invention. 2...metal halide lamp, 3...arc,
4, 5, 11, 13, 14...lens, 6, 16
...Incidence slit, 7,17...Diffraction grating, 8,
10, 15... Mirror, 9, 18... Output slit, 12... Micro flow cell, 19... Fluorescence measurement detector, 20... Transmitted light measurement detector, 2
1, 22...Amplifier, 23...LOG converter, 2
4...damping circuit, 25...recording device.

Claims (1)

[Scope of Claims] 1. A photometer comprising a light source, an optical system, a sample cell, and a detection system, characterized in that a metal halide lamp is used as the light source, and the detection system is composed of a transmitted light measurement channel and a fluorescence measurement channel. photometer. 2. The photometer according to claim 1, wherein the metal halide lamp is one containing tantalum iodide and mercury, and is installed so that the longitudinal direction of the arc is vertical. 3. The optical system has an excitation side spectrometer and a fluorescence side spectrometer, and each slit in each of the spectrometers is installed vertically so that its longitudinal direction coincides with the longitudinal direction of the arc of the metal halide lamp, 3. The photometer according to claim 1, wherein said sample cell is also elongated in the vertical direction. 4. The transmitted light measurement channel of the detection system is provided with a damping circuit for reducing noise with a frequency of 1 Hz or more.
The photometer according to item 3 or item 3. 5 The transmitted light measurement channel of the detection system includes:
A photometer according to claim 1, 2, or 3, further comprising a LOG conversion means and a damping circuit. 6. The detection system is configured to simultaneously perform transmitted light signal processing in the transmitted light measurement channel and fluorescence signal processing in the fluorescence measurement channel and send out outputs in parallel.
The photometer according to item 1 or 2 or 3 or 4 or 5.