JPS61105445A - Flow cell for measuring light absorbancy - Google Patents

Abstract

PURPOSE:To eliminate the influence of the refractive index of a measuring liquid by providing a long-sized cylindrical optical path provided with a liquid inlet and liquid outlet and constituting a light incident face of a planoconvex lens. CONSTITUTION:The liquid inlet 2, the liquid outlet 3, the long-sized cylindrical optical path 4 and the planoconvex lens 5, etc. are provided. The flow cell is so constituted that the wavelength light of a wax. incident angle is also irradiated to a photodiode 8 through a transmission face without striking against the inside wall of the optical path 4. The refraction of the light at the boundary face between the lens 5 and the liquid changes when the refractive index changes as a result of the change of the liquid to be introduced into the path 4 and therefore the transmission state of the light is subjected to the change as well but since the focal length of the lens 5 is adjusted to about the same as the optical path length, the reflection of the measuring light at the inside wall of the optical path does not arise within the range of the ordinarily considered refractive index changes. As a result the change of the intensity of the transmitted light owing to the change of the refractive index does not arise and the influence by said refractive index change is eliminated.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a flow cell for measuring absorbance.

More specifically, it relates to Flow 7A/ for absorbance measurement, which can be used to measure absorbance from ultraviolet to visible light, and is particularly useful as a measurement cell in an absorption detector in liquid chromatography.

(b) Prior Art Conventionally, flow 7~ has been used in clinical automatic analyzers and liquid chromatography absorbance detectors. Among these, 70-Seμ for liquid chromatographies is designed to have a long cylindrical shape or a long cylindrical shape for the two purposes of (1) reducing the cell capacity, and (2) increasing the rounding optical path length to increase sensitivity. A type of optical path having a shape of Optical systems in which the syslit is omitted by using this are also known. However, in such a long cylindrical optical path, a part of the measurement light incident from the incident surface often hits the inner wall and is reflected or dispersed, and the ratio of the reflected/dispersed light to the incident light is small. Since this changes depending on the refractive index of the sample liquid in the flow cell, there is a problem in that it is detected as if it were a change in absorbance, resulting in an error.

Regarding this point, Japanese Unexamined Patent Publication No. 1983-33 Eltsu No. 1 states:
Instead of the elongated cylindrical optical path described above, there is a proposal to use a truncated pyramidal optical path whose aperture tapers from the incident surface to the transmission surface. However, this cell has the disadvantage that the cell capacity is larger than that of the cylindrical upper μ cell, and furthermore, it is difficult to manufacture and process, resulting in high cost. On the other hand, Japanese Patent Application Laid-Open No. 58-158538 uses a cylindrical 7μ lens (with multiple optical apertures) and a combination of multiple lenses so that the measuring light passes only around the central axis of the 7μ lens. Proposals have been made to use such optical systems. However, this optical system has the disadvantage that it requires a large number of components, is complex in setting and assembling 1+-μ, and is expensive.

(#υPurpose This invention was made in view of the above situation,
The present invention aims to provide a flow cell that can eliminate the influence of the refractive index of the measuring liquid without using a complicated optical system and without increasing the cell capacity.

B) Structure According to the present invention, there is provided an absorbance I-traveling flow, characterized in that it has an elongated cylindrical optical path with a liquid inlet and a liquid outlet, and the light incident surface is constituted by a plano-convex lens. ~ is provided.

The radius of curvature of the plano-convex lens is adjusted so that the light entering the cell 70 is transmitted through the cell 70 without hitting the inner wall of the cell 70. This radius of curvature also depends on the angle of incidence of the incident light with respect to the 70-7p axis, but considering the range of variation of the angle of incidence set in a normal liquid chromatography detector, the focal length of the plano-convex lens is It is appropriate to adjust the optical path length to be approximately the same as the optical path length of the long cylindrical optical path.

On the other hand, the 7μ material and liquid inlet that set the long cylindrical optical path,
A known shape can be used for the liquid outlet. Further, the material of the plano-convex lens can be selected from various materials such as soda glass and quartz gaff depending on the type of measurement light.

In this invention, it is essential that the plano-convex lens be set at the light incident surface of 7μ, but in some cases it may be
It is also possible to set it on the light transmitting surface of Another advantage is that it can be installed in an optical system without distinguishing between the incident surface and the transmission surface.

Further, the 70-7μ of the present invention is not limited to a long cylindrical shape, but may be a long rectangular tube shape, and may also be provided with another optical path for comparison.

(e) Examples The flow cell for absorbance measurement of the present invention will be explained below using examples.

FIG. 1 is a configuration explanatory diagram showing an absorbance detector for liquid chromatography using the flow cell for absorbance measurement of the present invention, FIG. 2 is a perspective view showing the absorbance measurement flow cell μ of the present invention, and FIG. 3 shows a cross-sectional view taken along line A-A in FIG. 2.

In the figure, the absorbance measurement 70-cell 1v (1) has a liquid inlet (2) connected to a sample inlet pipe (21) with a diameter of 0.6++w and a sample outlet pipe (31) with a diameter of 0.6 m. It consists of a cylindrical stainless steel block with a long cylindrical optical path (4) with a diameter of 1 sw equipped with a liquid outlet (5) to be connected, and a flat quartz block on the light incidence side. The convex lens (5) is a tearless gasket (51; thickness 0.2 tm
) so that the convex surface is on the outside and the flat surface is on the inside, forming a light entrance surface. On the other hand, there is also a plano-convex lens (6) on the transmission surface side of the optical path (4) (Teflon gasket) (6
1), a light transmitting surface having a diaphragm function is configured. In addition, a control optical path is provided parallel to the optical path axis of ())-optical path (4), and the optical path (4) is
It is a long cylindrical cavity with the same shape.

Note that the focal length of the plano-convex lens (5) is approximately the same as the optical path length (for example, 1aR) of the optical path (4) (for example, ICR).
has been adjusted.

On the other hand, the optical system is composed of a light source (9), a concave mirror (10), a diffraction grating (11), and a silicon photodiode (8). (91) is positioned so that it is irradiated simultaneously and parallel to the optical paths (4) and ()). Photodiodes (8) are connected to optical paths (5) and (7), respectively.
The intensity of the measurement wavelength light that has passed through is photoelectrically converted and sent to the control display section, and from the difference between the two outputs, the absorbance on the optical path (4) is calculated and shown. In an optical system using a blow cell,
The transmission shapes when the incident angle of the wavelength light (91) is the maximum (incident angle 5.7°) are also shown in FIG.

Since a plano-convex lens is used on the incident surface in this way, even the wavelength light at the maximum angle of incidence as shown in the figure is irradiated onto the photodiode (8) through the transmission surface without hitting the inner wall of the optical path (4). That will happen. and a liquid introduced into the optical path,
For example, liquid chromatography eluents (methanol,
When the refractive index changes due to changes in the liquid (water, THF, buffer, etc.), the refraction of light at the interface between the plano-convex lens and the liquid changes, so the width of the light transmission also changes, but the focal point of the plano-convex lens changes. Since the distance is adjusted to the same extent as the optical path length, reflection of the measurement light on the inner wall of the optical path does not occur within the range of refractive index changes that are normally considered.

As a result, the transmitted light intensity does not change due to a change in the refractive index, and the influence thereof can be eliminated.

(F) Effects As described above, 1. According to the flow cell for absorbance measurement of the present invention, absorbance measurement can be performed without being affected by changes in the refractive index of the measurement liquid. Further, since there is no need to use any special component parts and it is easy to assemble, the cost is also reduced. Moreover, it has the advantage that it does not require a strict optical system and can be applied as is to conventional optical systems.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram illustrating an absorbance detector for liquid chromatography using the flow cell for absorbance measurement of the present invention, and FIG. 2 is a flowchart for absorbance measurement according to the present invention.
FIG. 3 is an explanatory diagram including a sectional view taken along the line A-A in FIG. 2. (1)...flow cell for absorbance measurement, (2)...liquid inlet, (3)...liquid outlet, (4)...long cylindrical optical path, (5)...plano-convex lens .

Claims (2)

[Claims] (1) A flow cell for measuring absorbance, characterized in that it has an elongated cylindrical optical path with a liquid inlet and a liquid outlet, and a light incident surface is constructed of a plano-convex lens. (2) The flow cell according to claim 1, wherein the focal length of the plano-convex lens is adjusted to be substantially the same as the optical path length of the elongated cylindrical optical path.