JPH05302893A - Spectral characteristics measuring device for trace liquid samples - Google Patents

Abstract

PURPOSE:To enable measurement of the spectral characteristic of a minute-amount liquid sample by a method wherein a capillary tube is made to suck liquid to be measured, from one end thereof, by a capillary action and to hold it and the tube is cut at an appropriate length from the suction side end thereof so that the part holding the liquid is included, and is made to be supported fixedly by a measuring part. CONSTITUTION:One end of a capillary tube 1 is dipped a little below the level of a sample vessel 2 in which a sample liquid 3 is put, and the sample liquid 3 is introduced into the tube 1 by utilizing a capillary action. The tube 1 is cut at a prescribed length (h) from the end face thereof and a tube fragment 4 thus prepared is set in a measuring part of a spectrophotometer so that the central axis thereof is parallel to the optical axis of measurement. When the dimension of a light flux in the measuring part is assumed to be 1mm and when the bore of the capillary tube 1 is set at phi2mm, for instance, and an optical path (d) at 1mm in view of some margin for positional precision, positional reproducibility, etc., in the case when the tube fragment 4 is supported by the measuring part, the amount of the sample liquid 3 held in the fragment 4 is about 3mul. On condition that the bore is about phi2mm and the liquid is an ordinary one, suction to a height of about 1mm can be attained sufficiently by the capillary action.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring an extremely small amount of sample liquid in a spectrophotometer for measuring the spectral characteristics of a sample in the visible / ultraviolet region or the like.

[0002]

2. Description of the Related Art A visible / ultraviolet spectrophotometer is an analytical instrument widely used for various purposes in the field of analytical chemistry. Although its application fields are diverse, the main purpose is to measure the spectral transmission characteristics of a sample, which is generally a liquid, in the unit of absorbance, which is proportional to the concentration of the sample, and to analyze the sample qualitatively or quantitatively. I often do it. With the progress of so-called biotechnology-related technologies in recent years, the role played by a spectrophotometer in the field of biochemical analysis has increased, as in other conventional fields. Therefore, as a problem required for spectroscopic analysis in the field of biochemistry including analysis of proteins and DNA, the number of samples to be measured is extremely small, valuable, and expensive, and a very small amount of sample liquid is used. It has happened that qualitative or quantitative analysis must be done. In particular, in the case of DNA-related analysis, the total sample volume is often several hundred μl or less, and this sample is used for measurement by a spectrophotometer because it is dispersed for various analyzers and research in the next stage. Volumes from a few μl to at most tens of μ
In most cases, it is 1 or less. Conventionally, as a means for measuring the absorbance of such a minute amount of liquid, a spectrophotometer in which the dimension of the luminous flux in the measurement analysis is made as small as possible by a luminous flux diaphragm or a condensing optical system, or an accessory device thereof. And a special sample container for carrying a microfluidic sample on this measuring part has been used.

As the special sample container which has been conventionally used, several types are known. Among them, the most widely used one is the optical path length used for ordinary spectroscopic analysis. A method of using a special prismatic cell whose optical path width and optical path height are reduced in order to reduce the internal volume based on the shape of a 10 mm prismatic cell, or a sample is introduced into a quartz glass capillary tube by a capillary phenomenon, A method has been known in which a central axis is supported by a measuring portion of a spectrophotometer so that it is perpendicular to a measurement optical axis of the spectrophotometer, and a condensing means such as a cylindrical lens is used together. Further, as a means for supporting and fixing these containers to the sample measuring part of the spectrophotometer, a commonly used holder for a 10 mm square cell is basically used and improved, or a means for positioning and fixing a thin tube by a leaf spring or the like. Was known.

Each of these conventional techniques has the following problems. First, a minute amount cell of a rectangular cell which is the first conventional example will be described. FIG. 8 shows a general schematic structure of a conventional prismatic minute amount cell. The square minute amount cell 21 has a bottom surface (a × b in FIG. 8A) having the same shape as that of a normal 10 mm square cell for spectroscopic analysis, and has a structure in which the volume of the portion into which the sample is put is minimized. Is. The bottom shape is the same as that of a normal prismatic cell so that the cell can be held by a regular cell holder for prismatic cells. In the example of FIG. 8, the portion into which the sample is put, that is, the measurement unit 22 has a dimension = height h × optical path width w
(See FIG. 8B), which corresponds to the optical path length d (see FIG. 8A). The taper portion 23 formed on the upper portion of this portion is provided so that the sample can be easily introduced and discharged by a pipette, a syringe or the like. Note that FIG. 8B
Shows a cross section taken along line GG in FIG. 8A, and FIG. 8C shows a state in which the sample liquid 3 is injected into FIG. 8B. Conventionally, when a small amount of liquid is measured using this prismatic minute amount cell 21, after the sample is injected into the measuring unit 22 by a pipette or the like, the ordinary rectangular cell provided in the measuring unit of the spectrophotometer is held. The prism small amount cell 21 is fixed to the cell holder to be measured, and the measuring light K is adjusted by the luminous flux diaphragm 5 having an appropriate shape.
The measurement was performed after limiting the luminous flux to the measurement unit 22 only. In this case, the size of the light beam limited by the light beam diaphragm 5 is determined by another part of the spectrophotometer, for example,
Since it is necessary to satisfy the optical performance required for a light source spectroscope, a photometric system, a detector, etc., it cannot be made smaller than a certain limit, and the limit is 1 mm × for a normal spectrophotometer.
It is about 1 mm or φ1 mm. Therefore, the sample is illuminated with the light flux of this magnitude. Further, in consideration of the position reproduction accuracy due to the attachment and detachment of the square minute amount cell 21, the dimension of the measuring portion 22 of the square minute amount cell 21 is approximately w =
The lower limit was about 2 mm and h = 2 to 2.5 mm.
Furthermore, when the sample liquid 3 is injected into the rectangular minute amount cell 21, the liquid surface does not become a flat surface due to surface tension, and generally a concave surface as shown in FIG. 8C is formed, so that the liquid surface is assumed to be a flat surface. It required more sample volume than it did.

Due to these optical restrictions and restrictions due to the liquid surface shape, if the optical path length d of the cell is d = 10 mm,
The minimum amount of liquid required for measurement was about 50 μl as a lower limit, and measurement with a liquid amount less than this was extremely difficult. In addition, although the rectangular minute amount cell 21 has the taper portion 23 formed so as to be convenient for injecting the sample liquid, the space for inserting the liquid is small when the once injected sample liquid 3 is collected and the cell is washed. Therefore, it was extremely difficult. Furthermore, in order to enable measurement in the ultraviolet region required in the biochemistry field,
The cell is generally a fused fusion processed product of quartz glass, but it has a drawback that the cost of the cell is extremely high because the material is expensive and the processing is difficult.
As a method of further reducing the required liquid amount by applying this cell, a method of reducing the optical path length d can be considered. For example, in order to set the sample amount to 5 μl, d = 1 mm must be set, Since the area of the liquid injection port is greatly reduced, the sample injection / recovery and cell cleaning can be performed by d =
It was more difficult than the case of 10 mm, and it was not a practical method. Also, in order to save the trouble of collecting the sample and cleaning the cell, a method of disposing the cell may be considered, but as described above, if the cell itself is extremely expensive, if the sample cannot be collected, Since it is required to reduce the liquid volume to several μl or less, this was also practically impossible.

Next, FIG. 10 shows a method using a quartz tube which is a second conventional example. In this method, the sample liquid 3 is sucked into the thin tube 31 made of quartz glass by utilizing the capillary phenomenon.
This is a method in which the tube axis is installed in the measuring section of the spectrophotometer so that the tube axis is orthogonal to the measuring optical axis, and the condensing optical system such as the cylindrical lens 32 shown in FIG. According to this method, the introduction of the sample solution, which is a problem in the prismatic cell, can be performed relatively easily by utilizing the capillary phenomenon. Further, the sample liquid can be easily recovered from the quartz thin tube and the thin tube can be washed by using air pressure or the like. However,
In the case of this method, generally, the quartz thin tube 31 having a cylindrical shape and the sample liquid 3 held therein act as a kind of cylindrical lens, so that the shape of the light flux entering and exiting the thin tube 31 is determined by other portions of the spectrophotometer. There is a problem that the cylindrical lens 32 or an optical system equivalent to this is always required for shaping in accordance with the above. For example, in order to make the sample volume 5 μl and the sample liquid level height 3 mm, the inner diameter of the quartz capillary should be about 10.4 mm, and an extremely strong cylindrical lens with a radius of curvature of about 0.7 mm should be measured. There is a problem in that an optical system for correcting this, if installed in the optical path, must be added. Further, the quartz thin tube 31 needs an expensive quartz glass having a transmittance even in the ultraviolet region in order to have optical performance enough to endure the spectral transmission measurement on both the inner and outer surfaces, that is, surface roughness, shape accuracy and the like. Material costs,
There is a problem that the processing cost becomes expensive. Furthermore,
Since the outer wall of the thin tube is a surface with a large curvature, it is extremely difficult to prevent the measurement light from passing through the quartz glass tube wall, and it is necessary to measure the sample transmitted light and the tube wall transmitted light together. Therefore, there is a problem that the accuracy of the absorbance measurement is lowered.

Further, the means for fixing these conventional containers to the measuring portion of the spectrophotometer has the following problems. FIG. 9 shows a conventional example of a cell holder for a square micro cell.
Similar to FIG. 8, the rectangular minute amount cell 21 into which the sample liquid 3 is injected is inserted into the cell holder 24 and fixed by the leaf spring 17. The cell holder 25 is fixed to the base plate 26, and is fixed to the sample measuring section of the spectrophotometer by a mounting hole 26A. Reference numeral 27 is a cell height adjusting mechanism using a screw or the like, which adjusts in the direction of arrow E in FIG. 9 to make the insertion depth of the cell variable. As described above, in this mechanism, the sample amount is extremely small and the liquid portion to be measured is often slightly larger than the light beam diaphragm 5 through which the light beam passes. At a position in the height direction where the luminous flux is illuminated,
This is for adjusting the square minute amount cell 21. In this cell holder 24, since the cell 21 is extremely small, if the positioning leaf spring 25 is made too strong, the cell 2
1 becomes difficult to attach and detach, and weakening the leaf spring 25 causes a problem that the position reproducibility when the cell 21 is attached and detached becomes poor. In addition, the height must be adjusted by the adjusting mechanism 27 in accordance with the injected sample liquid amount, and further, when there is looseness in the adjusting mechanism portion, it is said that the reproducibility when the cell 21 is detached is also poor. There was a problem. Furthermore, since a small cell is accurately positioned and fixed and an adjustment mechanism is required, the overall configuration is complicated and the cost is high.

FIG. 11 shows a second conventional example of a quartz capillary holder. As shown in FIG. 11, the thin tube 31 into which the sample liquid 3 has been sucked is inserted into the V groove 33A of the holder 33, and is fixed by the holding spring 24 attached to the holder 33. The attachment to the spectrophotometer is performed through the attachment hole 26A of the base plate 26 as in FIG. Reference numeral 32 is a cylindrical lens for correcting the lens effect due to the same thin tube as shown in FIG. This holder 33
According to this, it is possible to facilitate the attachment and detachment by making the thin tube longer than the measuring portion, and the positioning mechanism using the V groove 33A accurately positions the thin tube 31 on the measurement optical axis. can do. Since it is easier to introduce the sample liquid 3 into the thin tube as compared with the above-mentioned square micro-cell 21, the liquid level can have a margin as compared with the light flux diaphragm 35, and a height adjustment mechanism can be provided. It can be unnecessary. Although this method has the above advantages, on the other hand, this structure has the following drawbacks. Thin tube 3
1 is generally a thin-walled small-diameter quartz tube, which is difficult to handle and may be damaged during desorption, and as described above,
In order to correct the lens effect of the thin tube, a cylindrical lens 32 which is an expensive aspherical element is required, and in order to accurately position and fix the thin tube 31 in the axial direction of its relatively large dimension, a V groove portion and a pressing spring mechanism are provided. Etc. require high-precision processing.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a spectrophotometer for measuring the spectral characteristics of a sample in the visible / ultraviolet region, which is used as a cell material when the amount of the liquid sample to be measured is extremely small. It is an object of the present invention to be able to measure its spectral characteristics without using an expensive one and without requiring a special auxiliary optical system.

[0010]

A liquid to be measured is sucked and held from one end of the thin pipe by a capillary phenomenon or suction means, and the suction side of the thin pipe includes a portion holding the liquid to be measured in this state. Cut a thin tube with an appropriate length from the end, and support and fix the cut part of the thin tube holding the liquid to be measured inside the measuring part of the spectrophotometer so that its central axis is parallel to the measurement optical axis. The measurement of the spectral characteristics of a small amount of liquid sample was performed.

[0011]

According to the present invention, the sample liquid is injected into the thin tube by sucking the sample liquid into the thin tube by the capillary phenomenon or the suction means, and the thin tube portion filled with the sample liquid is cut and cut. The thin tube piece is installed in the measurement unit so that its central axis is parallel to the measurement optical axis. Therefore, the diameter of the sample solution can be determined by the inner diameter of the thin tube, and it is possible to make the thin tube as thin as possible, but as described above, the light flux size in the measurement section of the spectrophotometer should be made smaller. However, there is a practically extremely difficult limit, and this is temporarily set to φ1 mm. The inner diameter of the thin tube 1 is set to φ2 with some allowance for the position accuracy and position reproducibility when supporting the thin tube fragment 4 on the spectrophotometer measuring section.
In the case of mm and the optical path length d = 1 mm, the amount of the sample liquid 3 retained in the capillary fragments is about 3 μl.
If the inner diameter is about 2 mm, it depends on the properties of the sample, but if it is an ordinary liquid, the height is 1 m due to the capillary phenomenon.
Suction up to about m is possible. Further, in the case of the present invention, the measurement light is transmitted only by the sample liquid if the luminous flux size is sufficiently limited and the capillary diameter is appropriately selected, and there is no cell wall before and after the sample liquid, Even if it is necessary to measure the ultraviolet range, the thin tube does not need any optical characteristics such as transmission characteristics and surface roughness, and in extreme cases, it can be made of opaque material. Therefore, various inexpensive materials and manufacturing methods can be appropriately selected and manufactured. Specifically, glass molded products and injection or extrusion molded products of hard plastics such as styrene and acrylic are suitable. However, in some cases, the thin tube is not required to have optical characteristics, and thus it is possible to use metal such as stainless steel or ceramic. It is also easy to prevent the measurement light flux from passing through the cell wall around the sample, so that only the sample transmitted light can be measured purely. The required sample amount is extremely small as described above and the thin tube 1
Since it is possible to manufacture the sample at a low cost, it is possible to discard this together with the capillary fragments 4 when it is not necessary to collect the sample. If collection is required,
The sample liquid 3 may be collected from the thin tube fragment 4 by air pressure or the like, and only the thin tube fragment 4 may be discarded, which eliminates the trouble of washing the container, which has been a problem in the conventional square minute amount cell or the like. Also in this case, the rest of the thin tube 1 other than the fragments 4 can be repeatedly used as described above as long as its length is practical.

[0012]

FIG. 1 shows an embodiment of the present invention. First, as shown in FIG. 1A, one end of the thin tube 1 is slightly dipped into the liquid surface of the sample container 2 containing the sample liquid 3 synthesized by a reaction device or the like, and the capillary phenomenon is utilized to make the sample liquid 3
Is introduced into the capillary 1. Vacuum pump and dropper,
You may use suction means, such as a syringe, together. As shown in FIG. 2, make the rear end of the thin tube 1 thick and attach a rubber ball 8 to it.
The thin tube itself may be made like a Komagome pipette. The sample solution does not need to be filled over the entire thin tube, and it is sufficient to suck the sample solution to a height of about 0.5 to 1 mm, although it depends on the absorbance of the sample solution. Even if the thin tube 1 is separated from the liquid surface in this state, the sample liquid 3 is retained in the thin tube 1 by the surface tension. Next, as shown in FIG. 1B, the thin tube 1 is cut from the end surface at a constant length h. The length h may be appropriately determined depending on the filling state of the liquid, and may be determined, for example, at an intermediate position between the end surface of the thin tube and the height of the liquid surface in the thin tube. As a method of cutting the thin tube 1 into a predetermined length,
As shown in FIG. 2, the thin tube 1 is provided with marking lines 6 on the outer periphery at a predetermined interval d (equal to h in FIG. 1B) so that the measuring thin tube fragments 4 can be easily broken off. The distance d between the engraved lines may be selected so as to have a predetermined measurement optical path length according to the characteristics of the liquid, the tube diameter, etc. Further, as the material of the thin tube 1, the thin tube 1 is not irradiated with the measuring light. There is no optical restriction on the material and the manufacturing method of the thin tube, and therefore, the thin tube is made of a material having a low fracture brittleness, that is, a material in which the thin tube fragment 4 is easily broken, such as glass or hard plastic. It becomes easy to fold off with the score line 6 of 1. Further, the remaining portion of the thin tube can be used for the next measurement as long as the entire length L thereof can be used sufficiently. The thin tube inner diameter D may be appropriately selected and determined in advance according to the properties of the sample liquid and the amount of the measured liquid.

FIG. 3 shows an example of a jig for setting the above-described sample cell of the present invention at a predetermined position. This jig has a rectangular bottom shape of 10 mm × 10 mm, and has a shape adapted to a cell holder for setting a normal cell of a spectrophotometer. When the V-groove 7 is formed on the upper surface and the sample cell described above is placed on the V-groove, the axis of the cell 4 automatically coincides with the optical axis of the measurement light of the spectrophotometer.

FIG. 4 shows an example of a capillary fixing device for fixing the capillary to a jig during measurement, which also serves as a tool for breaking off the portion where the sample is sucked from the marked capillary. The sample liquid 3 is sucked into the thin tube 1 as shown in FIG. 2 by the method as shown in FIG. 1A or FIG.
The V-groove 11A, which is placed in accordance with one V-groove 11A, has a length substantially equal to the interval d of the thin tube, and a breaking space 11B is formed behind it. Fixture upper member 12
Is overlaid on the lower member 11. Upper member 12 and lower member 11
V groove 12A is formed in the same manner as the above, and its length is 1
Similar to 1A, it is almost equal to d, and a breaking space 12B is formed at the rear side like the lower member 11. The thin tube 1 is positioned by being sandwiched between the two V-shaped grooves 11A and 12A. The upper and lower members 11 and 12 are fixed by fixing screws 13. Reference numeral 14 denotes a breaking tool, which has a through hole 14A at its center, and the hole diameter is set to be slightly larger than the outer diameter of the thin tube 1. The breaking tool 1 is previously attached to the thin tube 1 fixed by the fixing tool upper and lower members 11 and 12.
Insert 4. The thin tube 1 is placed in these V grooves 11A and 12A
FIG. 5 shows a cross-sectional view of the center of the thin tube in the state in which is inserted.

In FIG. 5, the breaking tool 14 holds the thin tube 1 inside and is inserted into the breaking spaces 11B and 12B formed by the fixing tool upper and lower members 11 and 12, respectively. The thin tube 1 has a fixing member 11 from the end of the engraved line 6 at the tip thereof,
It is fixed by 12. Breaking tool 14 in this state
5 in the direction of the arrow in FIG. 5 to break the thin tube 1 by a predetermined dimension d and leave it in the fixture upper and lower members 11, 12.
Other parts can be removed. Reference numeral 3 is a sample liquid sucked into the thin tube 1. According to this fixing method, a short piece of an axially symmetric cylindrical tube may be fixed so that its axis is located at a predetermined position. Therefore, when fixing a rectangular parallelepiped rectangular cell, a small length of a narrow tube is fixed. Compared with the conventional example in which a certain piece is positioned so that its axis is perpendicular to the optical axis, the positioning and fixing can be performed with a simpler structure and with higher accuracy. The thin tube fragment 4 filled with the liquid thus cut is shown in FIG. 1C. As shown in FIG. 1D, the thin tube piece 4 is supported in the measurement part of the spectrophotometer so that its central axis is parallel to the measurement optical axis, and a light flux stop 5 for limiting the light flux size is used together. Then, the absorbance of the sample liquid 3 is measured.

FIG. 6 shows an example of a fixing member on the spectrophotometer side in this case. The broken and fixed thin tube piece 4 is attached to the measuring part of the spectrophotometer together with the fixture upper and lower members 11 and 12. A fixture holder 15 is attached to the spectrophotometer measuring portion through a mounting hole 15A, and a fixture combination product A holding the thin tube fragments 4 by a leaf spring 16 of the holder 15.
Position and fix. Reference numeral 17 is a light beam diaphragm. In this example, the fixture combination product A is fixed by a method similar to the case of the square cell of the conventional example, but unlike the case of the square cell, the fixture combination product A has restrictions in shape and material. Therefore, the positioning accuracy and the reproducibility of attachment / detachment can be easily improved as compared with the case of the square cell holder by, for example, forming a positioning pin or a positioning groove, fixing with a fastening component such as a screw, and the like.

FIG. 7 shows a fixture and a fixture holder when using positioning pins and screws. Fixture combination product A '
Has a positioning hole 18 formed therein, and is positioned with a positioning pin 20 fixed on a base plate 19 attached to a spectrophotometer (not shown) to position the fixture assembly A ′. To do. Further, in order to secure the fixing, the fixing tool combination is fixed with the fixing screw 13 '. According to this method, positioning and fixing of the fixture can be accurately and easily performed. The remaining portion of the thin tube broken off by the method shown in FIG. 5 is collected or discarded by a method such as blowing off the sample liquid remaining at the tip, or the portion including the liquid remaining portion is further cut and discarded to leave the remaining portion. The part can be used repeatedly while its length withstands use.

FIG. 1E is a view showing a cross section of the capillary segment 4 in the measuring state. The sample liquid 3 in the thin tube fragment 4 forms a curved surface due to the surface tension, but if the diameter of the thin tube 1 is appropriately selected, it does not become an extremely curved surface that becomes a problem in the prismatic minute cell shown in the above conventional example. Since the liquid surface has a curvature, the effect of the sample liquid 3 acting as a lens can be reduced to the extent that there is no problem in measurement. Even if an optical system for correcting the lens effect due to the curved surface formed by the liquid surface is added, since the curved surface is axisymmetric with respect to the optical axis, the correction optical system is also an aspherical surface such as an expensive cylindrical lens. It is possible to use only an inexpensive spherical lens without using any element. In the case of this measuring method, the length of the measuring light passing through the sample liquid 3, that is, the optical path length is the length d as shown in FIG. 1E. It is difficult to accurately reproduce this optical path length d because means for inhaling the sample by capillary action and cutting the capillary are used. However, for example, in a qualitative analysis in which an outline of an absorbance spectrum is known, such a variation does not pose a serious problem in practical use, and even when performing a quantitative analysis, Accurate quantification can be performed by measuring the absorbance at a wavelength of a wavelength or longer and performing a calculation to correct the optical path length error from the result.

[0019]

EFFECTS OF THE INVENTION According to the present invention, problems such as the limit of liquid amount, difficulty in sample injection / recovery and cell cleaning, which were present in the prior art, are solved, and the absorbance of an extremely minute amount of liquid is eliminated. Can be measured, and the container for containing the liquid can be manufactured at low cost. Therefore, the container can be disposable, the preparation for the measurement is reduced, and the measurement capability is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is a side view of an example of the thin tube in the above embodiment.

FIG. 3 is a perspective view of an example of a thin tube setting jig in the above embodiment.

FIG. 4 is a perspective view of an example of a thin tube fixing member in the above embodiment.

FIG. 5 is a cross-sectional view of an example of the thin tube fixing member in the above embodiment.

FIG. 6 is a perspective view of an example of a method of fixing a thin tube in the above embodiment.

FIG. 7 is a perspective view of another example of the method of fixing a thin tube in the above embodiment.

FIG. 8 is an explanatory diagram of a first conventional example.

FIG. 9 is a perspective view of an example of a holder of a first conventional example.

FIG. 10 is an explanatory diagram of a second conventional example.

FIG. 11 is a perspective view of an example of a holder of a second conventional example.

[Explanation of symbols]

 1 Capillary tube 2 Sample container 3 Sample liquid 4 Capillary tube fragment 5 Luminous diaphragm

Claims (2)

[Claims] 1. A capillarity or suction means for sucking and holding a liquid to be measured from one end of the thin pipe, and in this state, the thin pipe is attached from the suction side end of the thin pipe so as to include a portion holding the liquid to be measured. It is characterized in that it is cut and supported and fixed to the measurement part of the spectrophotometer so that the central axis of the cut part of the thin tube holding the liquid to be measured inside coincides with the measurement optical axis. Method for measuring spectral characteristics of trace liquid samples. 2. A thin tube having grooved lines or grooves formed at a predetermined interval, a fixing means for positioning and fixing the tip of the thin tube holding a liquid to be measured therein, and a tip of the thin tube with a scored line. An apparatus for measuring a small amount of a liquid sample, which is provided with a breaking means.