JPS623703Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an absorption photometer, and particularly to an absorption photometer suitable for highly sensitive detection of test components in a liquid sample.

[Background of the idea]

In conventional spectrophotometers that measure the absorbance of liquids, the light source chamber and sample storage chamber are open to the outside air.

Absorption photometers have made remarkable progress in recent years, and highly sensitive photometers with low noise and low drift have been provided. These low noises and low drifts have been achieved to a considerable extent through improvements in light source stabilization power supplies and signal processing systems such as electrical amplifier circuits. However, recent spectrophotometers are required to have even higher sensitivity.

The inventors of the present invention have studied how to increase the sensitivity of photometers and have found that fluctuation or movement of air within the optical system affects noise and drift of the photometer. Until now, this effect of air had not been recognized.

[Purpose of invention]

An object of the present invention is to provide a spectrophotometer that can perform highly sensitive measurements with significantly reduced noise during sample measurements.

[Summary of the idea]

In the present invention, in an absorption photometer equipped with a light source lamp, a flow cell through which the light from the light source lamp is transmitted, and a detection section that detects the transmitted light from the flow cell, one end of the light path cylinder made of a good thermal conductor is connected to the light source lamp. The other end of the optical path tube contacts the entrance side window surface of the flow cell to form an optical path that is shielded from outside air from the light source lamp surface to the flow cell, and this optical path is transparent. The light path tube is partitioned into a plurality of rooms by a flexible member, and the light path cylinder is covered with an outside air shielding room.

[Example of idea]

One of the causes of noise and drift that cannot be corrected even by electric circuits is due to the movement of the sample when the sample storage section is of a flow-through type. However, it has been found that even if this problem is solved, there are still things that cause noise and drift.

Generally, the light source of a photometer also serves as a heat source. Therefore, when the light source is open to the atmosphere, the air surrounding the light source is expanded and moved by heat conduction, radiation, convection, etc. from the light source. This movement of air brings about new movement of other air. Air movement occurs irregularly, giving rise to the so-called fluctuation phenomenon. When air moves along the optical path, it refracts the light and changes the amount of light that reaches the photodetector. Therefore, it causes noise and drift.

In order to eliminate the movement of gas in the optical path, it has been confirmed that it is effective to shield the area near the light emitting source through which the extracted light passes from the outside air. Furthermore, the measurement accuracy can be further improved by keeping the room through which the light passes at a constant temperature using a constant temperature device or by making the room through which the light passes substantially a vacuum.

Embodiments based on the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram for explaining one embodiment of the present invention.

A base plate 22 on which the low-pressure mercury lamp 1 forms part of an airtight chamber with a lamp support or socket 24.
is fixed. Virtual light beams a and b emitted from the light extraction part 3 in the center of the mercury lamp 1 are turned into parallel light beams by a condenser lens 6, pass through a flow cell consisting of a pair of cell windows 8 and a cell body 9, and pass through an optical filter 11. It reaches the photodetecting elements 12 and 12'. The lens 6 is closely held by an optical path tube 5 made of a good thermal conductor such as aluminum or copper. The tube 5 is tightly attached to the glass surface of the bulb of the low-pressure mercury lamp 1 by a seal portion 4 provided at the end.

The cell window 8 is made of quartz glass and is welded to an opaque cell body 9. The cell body 9 has cell communication holes 25 and 25' which form a double optical path through which the liquid to be measured passes. The surface of the entrance side window 8 of the flow cell is tightly connected to the optical path tube 5 via the packing 7. Filter 1 for extracting monochromatic light
1 is fixed to the detection block 14. Two sensing elements 12 and 12' are fixed to a sensing block 14 by an element fixing plate 13 and connected to a lead wire 19. The detection block chamber, ie, chamber E, is kept airtight by an O-ring 15 and a fixing screw 17 that holds a lid 16.

The cover 18 forming the H chamber is connected to the detection block 1.
4 and the cell holder 10. The coil pipe 20 held by the fixing plate 21 is provided to equilibrate the temperature of the liquid flowing into the flow cell with the temperature of the cell body 9, and is made of a metal pipe wound several times. The indoor partition plate 23 formed by the base plate 22 and the cover 26 serves to keep the heat generating part 2 near the filament on the light extraction part side. In this example, room F is an outside air shielded room.

In the above configuration, the part with the highest temperature in the low-pressure mercury lamp 1 is the heat generating part 2 where the filament is present, and the surrounding G chamber is in the highest temperature state. The partition plate 23 reduces the transfer of heat from the G room to the F room. The F chamber is located around the light extraction region 3 and has the second highest temperature after the G chamber. Chamber A formed by the optical path tube 5 and the lens 6 is brought into close contact with the glass surface of the mercury lamp 1 via a seal portion 4 made of felt, for example. The optical path tube 5 is tightly attached to the extent that there is no gas movement with the outside when the pressure inside the A chamber is normal. Chamber B, which is adjacent to chamber A, is formed by a lens 6, a cell window 8, and an optical path tube 5 so as to be airtight at normal pressure. Both chambers C and D are kept airtight so that outside air does not circulate therein.

In the above embodiment, the entire optical path from the light extraction part to the detection element is blocked from the outside air.
In places where there is a small temperature difference with the outside air, such as the room and room D, the increase in noise is small even when the room is open to the outside air.

Further, in the above-described embodiment, each of the rooms A, B, C, and D is placed in a sealed box to reduce the influence of temperature from outside air. That is, room A and room B
The chamber is surrounded on the outside by chamber F, chamber C and D
The chamber is surrounded on the outside by chamber H. This reduces the temperature difference with the outside air, and in particular reduces drift. Since each of the rooms A, B, C, and D is a small space, the temperature in each room is almost at equilibrium, and there is almost no movement of gas within the room.

By forming the optical path tube 5 from a material with excellent thermal conductivity, the interior of the room can reach equilibrium in a short time and have a heat dissipation effect.

FIG. 2 compares the magnitude of noise when the method based on FIG. 1 is adopted and when it is not adopted (conventional method). That is, FIG. 2A shows a case where the optical path tube 5, the partition plate 23, and the cover 26 are not provided, and the baseline absorbance change was 0.0005-OD. FIG. 2B is based on the configuration shown in FIG. 1, and the baseline absorbance change was 0.000025-OD. The noise level of B is 1/20 compared to A.
has decreased to In both cases, 1.0% methyl alcohol was added to the flow cell using a reciprocating piston pump.
This is data when flowing to the sample side at a flow rate of ml/min.

FIG. 3 is a block diagram of another embodiment based on the present invention. In this example, a tungsten lamp is used as the light source. The tungsten lamp 30 is fixed to the lamp base 31 by a lamp socket 33. The light emitted from the lamp 30 passes through a heat shield plate 36 and a lens 6 provided in the optical path tube 40, and then passes through the flow cell body 9. The lamp chamber N is formed by a cover 34 and a base 31. The N room has a ventilation hole 32, and natural ventilation or forced heat radiation by a ventilation fan 37 is performed as necessary. The partition plate 35, together with the optical path tube 40 and the base plate 22, forms a Q chamber that reduces the temperature difference between the L chamber and the M chamber with the outside air. The flow cell is housed in the P chamber. Other symbols are the same as in FIG. In this example, the Q room is an outside air shielded room.

In the above configuration, the K room, L room, M
Each room forms an independent sealed room, and the temperature in each room has reached equilibrium, so air movement due to heat can be kept to a minimum.
An optical path tube 40, which together with the heat shield plate 36 forms an external gas non-circulation chamber K, is closely attached to the glass surface of the lamp 30 via an elastic seal 4.

In general, a tungsten lamp has a heat generating part and a light extraction part in the same area, and has a large amount of heat generated. Therefore, the air around the lamp is most easily moved by heat. Therefore, the interior of the K chamber is substantially sealed by the seal 4 made of heat-resistant glass wool. Preferably, a vacuum is created inside the lamp 30 to eliminate gas movement within the lamp.

In this example, by dividing the optical path into multiple sealed rooms, the temperature of each room is equilibrated independently and fluid movement caused by heat is prevented, which greatly reduces noise and drift. can be reduced to

[Effect of idea]

As explained above, according to the present invention, since light passes through a room where there is no gas flow with the outside, noise is greatly reduced, making it possible to measure samples with extremely high sensitivity.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the configuration of an embodiment based on the present invention, Figure 2 is a diagram comparing the noise level between the conventional method and the embodiment of Figure 1, and Figure 3. FIG. 2 is a schematic cross-sectional view of another embodiment based on the present invention. 2... Heat generating part, 3... Light extraction part, 5,40
. . . Optical path cylinder, 6 . . . Lens, 11 . . . Optical filter, 12, 12' .

Claims (1)

[Scope of utility model registration request] In an absorption photometer equipped with a light source lamp, a flow cell through which light from the light source lamp is transmitted, and a detection section that detects the transmitted light from the flow cell, one end of an optical path cylinder made of a good thermal conductor is brought into contact with the surface of the light source lamp. The other end of the optical path cylinder is brought into contact with the entrance side window surface of the flow cell to form an optical path that is isolated from the outside air from the light source lamp surface to the flow cell, and this optical path is made of a light-transmitting member. An absorption photometer characterized in that the light path cylinder is partitioned into a plurality of rooms and covered with an outside air shielding room.