JPH10221168A - Spectrophotometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the effect of photochemical reactions of a sample by a measurement light when the sample is repeatedly measured. SOLUTION: A shutter 12 for shutting of light is set in front of a sample cell 13. When the sample is repeatedly measured via every predetermined time interval, a CPU 17 detects whether or not a time allowance for opening and closing the shutter 12 is present before a next measurement is started after one measurement is finished. With the allowance present, the shutter 12 is once closed to shut the light to the sample cell 13. The CPU 17 controls to open the shutter 12 at the next measurement to project the light to the sample cell 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrophotometer for measuring absorbance or the like by irradiating a sample with measurement light and detecting transmitted light or reflected light, and more particularly to a spectrophotometer for obtaining a temporal change in the absorbance or the like. The present invention relates to a spectrophotometer that repeatedly performs measurement at time intervals.

[0002]

2. Description of the Related Art FIG. 4 is a schematic diagram showing an example of an optical system of a general ultraviolet-visible spectrophotometer. Light emitted from a light source 10 such as a deuterium lamp or a tungsten iodine lamp contains various wavelengths, and monochromatic light having a predetermined wavelength is extracted as measurement light by a monochromator 11. The measurement light is applied to the sample cell 13 filled with the sample solution, and when the light passes through the sample cell 13, light having a wavelength specific to the sample is absorbed. The transmitted light is a photodetector 14
And absorbance or transmittance is calculated based on the detection signal.

[0003]

In the above-mentioned spectrophotometer,
In order to measure the time change of the absorbance or the transmittance, the measurement is often performed repeatedly at predetermined time intervals over a relatively long time. However, if the measurement light is continuously irradiated on the sample cell 13 over the entire period until the measurement is completed,
If the sample solution is a photochemically reactive substance,
The measurement light promotes an undesired reaction of the sample, which may hinder accurate measurement.

Conventionally, in a spectrophotometer using a deuterium lamp as the light source 10, if the lamp is left in a lighting state for a long time, the brightness is reduced. Some devices have a function of automatically turning off the lamp when a control command from the device is continued for a predetermined time or longer.
However, since such a function corresponds to, for example, forgetting to turn off the power of the spectrophotometer after the measurement is completed, the function does not function when the measurement is repeatedly performed at predetermined time intervals as described above. ing.

[0005] In such a repeated measurement,
It is practically difficult to prevent the sample cell 13 from being irradiated with the measurement light by turning on and off the light source 10. This is because the deuterium lamp requires time (several minutes to several tens of minutes) from when it is turned on until the light emission reaches a stable state, and after the lamp is turned on, the temperature inside the spectrophotometer rises and the whole is in thermal equilibrium. This is because it takes time to reach.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to reduce the influence of the photoreaction of a sample due to measurement light when performing measurement repeatedly for a long time. It is an object of the present invention to provide a spectrophotometer.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a spectrophotometer for irradiating a sample with light emitted from a light source and repeatedly and intermittently measuring transmitted light or reflected light. A) light blocking means for blocking light in the middle of the optical path from the light source to the sample; b) determination for determining whether or not the standby time in repeated measurement is longer than the operation time required for the light blocking and return of the light blocking means. Means, c) drive control means for driving the light-shielding means to cut off irradiation light on the sample within the standby time when the standby time is determined to be longer than the operation time by the determination means,
It is characterized by having.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a spectrophotometer according to the present invention, the light shielding means may use, for example, a shutter for mechanically blocking an optical path. Such a shutter requires an appropriate time for each of the closing (light shielding) operation and the opening (returning) operation. Therefore, the determination means obtains a waiting time from the end of one measurement of the repeated measurement to the next measurement, and the waiting time is an operation required for closing and opening the shutter. It is determined whether it is longer than the time. When the standby time is shorter than the operation time, there is no time margin for light blocking by the shutter, but when the standby time is longer than the operation time, there is sufficient time, so the drive control means closes the shutter once. To block the irradiation light on the sample. Then, the shutter is opened when the operation time required to open the shutter has elapsed since the next measurement. As a result, the irradiation light to the sample is cut off during the period in which the measurement is not performed within a range that does not hinder the repeated measurement.

The operating time required for closing and opening the shutter is usually determined by the configuration of the shutter. Therefore, when the time interval for repeated measurement is predetermined, the judgment means performs light shielding before the start of measurement. It can be determined whether or not there is enough time. Therefore, it is not necessary to determine whether or not the light is shielded for each measurement during repeated measurement.

[0010]

According to the spectrophotometer of the present invention, when the measurement is intermittently repeated at predetermined time intervals, the time during which the sample cell is irradiated with the measurement light can be minimized. For this reason, even if the sample is a substance having a high photochemical reaction activity, denaturation of the sample by the measurement light is reduced, and more accurate measurement can be performed.

[0011]

1 shows an embodiment of a spectrophotometer according to the present invention.
This will be described with reference to FIG. FIG. 1 is a configuration diagram of a main part of the spectrophotometer according to the present embodiment. In this spectrophotometer, a shutter 12 that can be opened and closed is provided on an optical path between a monochromator 11 and a sample cell 13, and the shutter 12 is driven by a shutter driving unit 15 including a motor and the like.
The control unit 16 includes a CPU 17 and a timer 18,
Reference numeral 17 controls the signal processing unit 20 so as to capture the detection signal of the photodetector 14 at a predetermined timing, and sends a shutter opening / closing signal to the shutter driving unit 15. The input unit 19 includes an input key operated by a measurer or a control signal processing unit from an external device, and is used to set parameters necessary for the processing operation of the CPU 17.

Hereinafter, the CPU 17 for repeatedly measuring the absorbance at predetermined time intervals in the spectrophotometer having the above configuration will be described.
Will be described with reference to the flowchart of FIG. When performing repeated measurement, the measurer inputs and sets the time interval of the repeated measurement and the measurement end time (elapsed time when the first measurement time point is set to zero) in the input unit 19.
Of course, instead of the measurement end time, the number of measurement repetitions may be input and set.

When the execution of the repetitive measurement program is started, the timer 18 starts counting time, and the CPU 17 sends a shutter release signal to the shutter drive unit 15 (step S).
1). As a result, the shutter 12 is opened, the monochromatic light extracted by the monochromator 11 is irradiated on the sample cell 13, and the transmitted light that has passed through the solution in the sample cell 13 reaches the photodetector 14. The CPU 17 gives an instruction for measurement to the signal processing unit 20, whereby the signal processing unit 20
The detection signal detected in step 4 is read and a predetermined calculation process is performed to calculate the absorbance (step S2).

After execution of the first measurement, the CPU 1
7 determines whether or not the current time t measured by the timer 18 has reached the measurement end time (step S3). When it is determined that the current time t has reached the measurement end time, a shutter closing signal is sent to the shutter driving unit 15 (step S11). This closes the shutter 12,
The measurement ends when the sample cell 13 is not irradiated with the measurement light.

If it is determined in step S3 that the current time t has not reached the measurement end time, the time required for closing and opening the shutter 12 (the time required for opening and closing the shutter) t1 is traced back from the next scheduled measurement time ta. The next shutter closing time ts is calculated (step S4), and then it is determined whether or not the current time t measured by the timer 18 has reached the next shutter closing time ts (step S4).
5). If the current time t has not reached the next shutter closing time ts, it is determined that there is enough time to close the shutter 12 and cut off the irradiation light, and a shutter closing signal is sent to the shutter driving unit 15 (step S6). As a result, the shutter 12 is closed, and the irradiation light to the sample cell 13 is blocked.

After the shutter 12 is closed, a time t2 required for opening the shutter 12 (a time required for opening the shutter) t2 and a next shutter opening time to which are traced a predetermined margin time α from the next scheduled time ta are calculated (step S7). ),
Subsequently, it is determined whether or not the current time t measured by the timer 18 has reached the next shutter release time to (step S8). Here, the predetermined margin time α is
Step S in the state where the shutter 12 is closed
8 is appropriately determined according to the repetition period of the determination of 8. That is, when the determination in step S8 is repeatedly performed at extremely short intervals, the margin time α can be made very small.

If it is determined in step S8 that the current time t has reached the next shutter release time to, a shutter release signal is sent to the shutter drive unit 15 (step S8).
9). As a result, the shutter 12 opens again, and the sample cell 13 is irradiated with monochromatic light extracted by the monochromator 11. Since the shutter release signal is always sent at the latest before the time when the shutter release required time t2 is traced back from the next scheduled measurement time ta, it is guaranteed that the shutter 12 will be opened by the next scheduled measurement time ta.

If it is determined in step S5 that the current time t has passed the next shutter closing time ts, there is not enough time to close the shutter 12, and the next measurement is performed with the shutter 12 opened. After waiting until the scheduled time ta (step S10), the next measurement is executed (step S2). After the shutter 12 is opened in step S9, the next measurement is similarly performed after waiting for the next scheduled measurement time ta. Of course, in this case, the standby time is an extremely short time within the maximum margin time α.

FIG. 3 is a diagram schematically showing the above processing operation on the time axis when the length of the time interval of the repeated measurement is different. FIG. 3A shows a case where the measurement time interval is longer than the shutter opening / closing required time t1, while FIG. 3B shows a case where the measurement time interval is shorter than the shutter opening / closing required time t1. In the case of FIG. 3A, there is a sufficient time until the next shutter closing time ts after the first measurement is completed. Therefore, the shutter 12 is closed to perform light shielding, and the current time t becomes the next shutter opening time to. Until it becomes possible, light shielding can be continued. On the other hand, in the case of FIG.
At the end of the first measurement, the next shutter closing time ts
Has already passed, so there is no time margin for opening and closing the shutter 12. Therefore, in this case, the sample cell 13 is continuously irradiated with light without shielding.

In the above embodiment, it is determined whether or not the opening and closing operation of the shutter 12 can be performed at the end of each measurement of the repetitive measurement. Therefore, the opening and closing of the shutter 12 can be controlled optimally even if the time interval of the repeated measurement is not constant. However, in general, the time interval of the repeated measurement is constant, and the time required for opening and closing the shutter is also predetermined. Therefore, in such a case, before the start of the measurement, it is determined whether or not the light can be shielded by determining whether or not the length of the time interval of the repeatedly set measurement that is input and set is longer than the required time for opening and closing the shutter. In addition, when it is determined that the light can be shielded, it is possible to determine at what timing before the next measurement the shutter release signal should be transmitted.

If the stability of the characteristics of the light source 10 at the time of ON / OFF and the thermal stability inside the spectrophotometer do not matter, the light source 10 may be used instead of shielding the light in the above embodiment. The light irradiation to the sample cell 13 may be intermittently performed by performing an ON / OFF operation. For example, in a double beam type spectrophotometer having two optical paths passing through the sample cell and the reference cell, the fluctuation of the light amount of the light source is canceled by the arithmetic processing, so that the time required for the ON / OFF operation of the light source is reduced. Relatively short. Further, in the tungsten iodine lamp, it takes less time until the light amount becomes stable when the lamp is turned on than in the deuterium lamp.

By the way, as in the above embodiment, the shutter 1
By adopting a configuration in which the irradiation light to the sample cell 13 can be intermittently operated by the method 2, the following spectroscopic measurement can also be performed. That is, in the configuration of FIG. 1, the irradiation time of light to the sample cell 13 can be adjusted by controlling the opening and closing operation of the shutter 12. Therefore, when it is desired to measure the activity of the photochemical reaction of the sample solution, the irradiation time of light to the sample cell 13 is managed, and the relationship between the irradiation time and the absorbance (or transmittance) is measured. In this case, when the wavelength of the light causing the photochemical reaction of the sample is not the same as the wavelength of the light for the transmittance measurement, the monochromator 11 may be controlled to take out monochromatic light having the optimum wavelength for each.

The spectrophotometer according to the present invention irradiates a sample directly with light emitted from a light source, disperses the transmitted light using a grating or the like, and obtains a PDA (photodiode array).
The present invention can also be applied to a so-called post-spectroscopy type spectrophotometer that leads to a multi-channel type detector such as an element.

Further, the above-described embodiment is merely an example, and it is apparent that variations and modifications can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of a spectrophotometer of the present invention.

FIG. 2 is a flowchart of a shutter opening / closing control operation in the embodiment.

FIG. 3 is a schematic diagram illustrating a relationship between a difference in a time interval of repeated measurement and a shutter opening / closing control operation in the embodiment.

FIG. 4 is a schematic configuration diagram of an optical system of a conventional ultraviolet-visible spectrophotometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Light source 12 ... Shutter 13 ... Sample cell 15 ... Shutter drive part 17 ... CPU 18 ... Timer 20 ... Signal processing part

Claims (1)

[Claims] 1. A spectrophotometer for irradiating a sample with light emitted from a light source and repeatedly and intermittently measuring transmitted light or reflected light, wherein: a) light blocking means for blocking light in the optical path from the light source to the sample B) determining means for determining whether or not the standby time in repeated measurement is longer than the operation time required for shading and returning of the light-shielding means; andc) if the standby time is longer than the operating time by the determining means. And a drive control means for driving the light shielding means so as to block the irradiation light to the sample within the waiting time when the determination is made.