JPH0726910B2 - Cylinder type variable length cell - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to spectroscopic measurement of liquids, and particularly to transmitted light measurement.

(Problems to be Solved by the Related Art and Invention) In transmitted light measurement of a liquid in the infrared region, a liquid is filled in a sample cell and the light transmitted through the cell is measured.

As a conventional method for handling a liquid sample in transmitted light measurement, there is, for example, a liquid film method (sandwich method). In this method, 1 to 2 drops of a liquid sample is sandwiched between two infrared window plates, and a thin liquid film is directly measured. The cell length (sample thickness) is adjusted by tightening the nut of the holder.

The advantages of this method are as follows.

(A) The operation is extremely easy and simple.

(B) Only the absorption of the sample can be measured over the entire wavelength without interference of other intervening substances.

(C) Easy measurement can be performed.

On the other hand, the drawbacks of this method are as follows.

(A) It is necessary to wipe the window plate after each measurement, and there is a possibility that the sample may be directly touched.

(B) The sample injection is a manual operation and continuous measurement cannot be performed.

(C) The cell length is determined by the tightening of the nut of the holder, and the reproducibility is not good.

(D) Not suitable for exact quantification.

On the other hand, there is a method of using a fixed cell or an assembled cell. In these cases, the cell length is accurate. However, in the case of a fixed cell having a fixed cell length, in the case of a thin cell length, there are drawbacks such that it is difficult to take a sample in and out, and it is difficult to produce a cell length of micron order. Further, it is difficult to handle a fixed cell or an assembled cell whose cell length is changed by a spacer.

Further, the conventional variable cell having a variable cell length has a complicated mechanism and is difficult to handle.

The object of the present invention is to simplify the structure and handling,
It is an object of the present invention to provide a variable length cell capable of quickly and accurately measuring transmitted light in the ultraviolet to infrared region of a liquid.

(Means for Solving the Problem) In a first cylinder type variable length cell according to the present invention, one end face is opened and an outer cylinder having a window plate portion on the other end face, and the above-mentioned one end face on which An inner cylinder that is provided with a window plate portion parallel to the window plate portion of the outer cylinder, is inserted into the outer cylinder, and is movable in the axial direction;
The branch pipe for injecting and discharging the sample between the window plate part of the outer cylinder and the window plate part of the inner cylinder, the holding means for holding the outer cylinder, and the window plate parts of the outer cylinder and the inner cylinder are almost A fine movement means for moving the inner cylinder inserted in the outer cylinder in the axial direction in a close contact state, and a distance longer than the distance that the fine movement means can move in the axial direction for the inner cylinder inserted in the outer cylinder. Based on the actual cell length measured value of the cell length of the sample between the window plate portion of the outer cylinder and the window plate portion of the inner cylinder, the coarse movement moving means and the coarse movement means. And a cell length control means for changing the cell length by controlling the cell length control amount of the fine movement moving means.

Preferably, the sample held between the window plate portion of the inner cylinder and the window plate portion of the inner cylinder is not exposed to light for the same sample in a state where there is almost no temperature change of the sample between the inner cylinder and the outer cylinder. The relational expression between the absorbance and the cell length is obtained in advance by measuring the absorbance and the cell length of the sample when the light is transmitted, and the above cell length control means measures the cell length of the sample between both window plate parts. The amount of movement of the inner cylinder by the fine movement moving means is controlled based on the value and the above relational expression.

Preferably, the fine movement moving means includes a piezoelectric actuator, and the coarse movement moving means includes a pulse stage using a pulse motor.

(Operation) In the first cylinder-type variable length cell according to the present invention, the inner cylinder is axially movably inserted into the open end of the outer cylinder.
The sample is injected between the window plate portion of the outer cylinder and the window plate portion of the inner cylinder by the branch pipe. In addition, the sample is discharged from the branch pipe as the sample is inserted in the inner cylinder. The holding means holds the outer cylinder and allows only the inner cylinder to move. The fine movement moving means moves the inner cylinder in a micron order, and the coarse movement moving means roughly moves the inner cylinder.

Further, in the second cylinder type variable length cell according to the present invention, in order to adjust the cell length more accurately, the actual spacing (cell length between the window plate portion of the outer cylinder and the window plate portion of the inner cylinder is controlled by the control means. )
Is calculated, and the amount of movement of the inner cylinder by the fine movement movement means and the coarse movement movement means is controlled based on the obtained actual interval value.

(Examples) Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a cross section of an example of a cylinder cell made of Pyrex glass according to the present invention. This cylinder type cell is composed of an outer cylinder 1 and an inner cylinder 11. The outer cylinder 1 and the inner cylinder 11 are respectively
It is provided with cylindrical portions 2 and 12. Outer cylinder 1 cylindrical part 2
One end of is open, and the inner cylinder 11 can be inserted into the outer cylinder 1. The inner surface of the cylindrical portion 2 of the outer cylinder and the outer surface of the cylindrical portion 12 of the inner cylinder are mating surfaces, and the inner cylinder 11 is movable in the axial direction of the cylinder while being in close contact with the outer cylinder 1.

One ends of the cylindrical portion 2 of the outer cylinder 1 and the cylindrical portion 12 of the inner cylinder 11 are formed as window plate portions 3 and 13 that transmit light, respectively.
That is, the window plate portions 3 and 13 are also made of Pyrex glass like the cylindrical portions 2 and 12, and are integrally manufactured with the cell body (1, 11). In order to inject the sample between the window plate portions 3 and 13, the two branch pipes 4 and 5 are provided near the window plate portion 3 of the cylindrical portion 2 of the outer cylinder 1 symmetrically with respect to the axis of the cylinder. It is provided.

It should be noted that flange portions 6 and 14 are provided at the other ends of the cylindrical portion 2 of the outer cylinder 1 and the cylindrical portion 12 of the inner cylinder 11, respectively. It can be operated to move in any direction.

The sample enters the space between the window plates 3 and 13 from one branch pipe 4 and exits from the other branch pipe 5. Sample thickness (cell length)
Is the distance between both window plate parts 3, 13. Therefore, the cell length can be easily changed by adjusting the distance between the window plate portions 3 and 13.

In the case of a liquid sample, as shown by the arrow in FIG. 2, a sufficient sample can be easily sucked by pulling out the inner cylinder 11 like a syringe. Excessive samples, mud, etc. are discharged from the branch pipe 5 to the outside. Then, the inner cylinder 11 is pushed in and stopped at a predetermined cell length. As a result, the cell length can be adjusted arbitrarily.

When the cell length is on the order of microns, the window plates 3 and 13 of the outer cylinder 1 and the inner cylinder 11 are in close contact with each other, but the pressure applied to the outer cylinder 1 by the inner cylinder 11 is adjusted to adjust the cell length. it can.

Next, with the cell length being constant, the cylindrical portion 2 of the outer cylinder 1 and the inner cylinder 11,
Light is incident on the sample parallel to the 12 axes and the transmission spectrum is measured. When the measurement is completed, the current sample is discharged and, if necessary, washed, and then the next sample is introduced to perform the next measurement. Washing can be done easily.

In this cylinder type cell, the window plate parts 3 and 13 and the cell main body (cylindrical part) 2 and 12 are made of one piece of Pyrex glass,
Since both cell bodies can be rubbed together, the structure can be simplified and the cost can be reduced.

To obtain an accurate cell length, as shown in FIG. 3, insert a ring 7 of constant thickness between the window plate parts 3 and 13 and
As shown in the figure, the inner cylinder 11 may be pressed against the outer cylinder 1 in the axial direction of the cylinder. Thereby, the cell length becomes equal to the thickness of the ring 7. The ring 7 is provided with a groove (not shown) so that the sample can move in and out.

When it is desired to obtain an accurate cell length on the order of micron, it is possible to perform adjustment using a uniaxial pulse stage 33 for coarse adjustment and a piezoelectric actuator 32 for fine adjustment as shown in FIG. That is, first, the outer cylinder 1 of the cylinder type variable length cell is fixed by the cell holder 31. On the other hand, a piezoelectric actuator 32 is fixed to the outside of the flange portion 14 of the inner cylinder 11, and the inner cylinder 11 can be moved in the order of micron by the voltage applied to the piezoelectric material (for example, PZT). The integral flange portion 14 and the piezoelectric actuator 32 are supported by a uniaxial pulse stage 33, and the uniaxial pulse stage 33 is mounted on a cylindrical shaft of the cylinder portion 2 of the outer cylinder 1 by a pulse motor 34 driven by a computer 35. Can move in parallel. In the case of adjusting the cell length, first, the position of the uniaxial pulse stage 33 is moved in the cylindrical axis direction to roughly adjust the cell length, and then the voltage applied to the piezoelectric actuator 32 is adjusted to finely adjust the cell length.

Here, in order to obtain a more accurate cell length, the cell length is calculated by the computer 35 based on the interference pitch (generated by the optical path difference between the cell lengths) obtained by spectrum scanning, and the value is fed back. Then, the piezoelectric actuator 32 is controlled.

Next, FIG. 6 shows a variable length cell made of stainless steel. This variable-length cell also includes an outer cylinder 101 and an inner cylinder 111, and the outer cylinder 101 and the inner cylinder 111 are provided with cylindrical cylindrical portions 102 and 112, respectively. The cylindrical portion 112 of the inner cylinder 111 is inserted into the cylindrical portion 102 of the outer cylinder 101, and two O-rings 11 are provided between the cylindrical portions 102 and 112.
Sealed by 3,114. Window plate portions 103, 115 (for example, made of ZnSe that transmits infrared rays) are fixed to one end surfaces of both cylindrical portions 102, 112 with a screw type ring (not shown), respectively. In order to introduce the sample into the space between both window plate portions 103 and 115, two branch pipes are provided at the end of the outer cylinder portion 102 on the window plate portion 103 side.
104 and 105 are attached. Further, flange portions 106 and 116 are provided at the other ends of both the cylindrical portions 102 and 112.

This stainless variable-length cell has a more complicated mechanism than the Pyrex glass variable-length cell shown in FIG. 1, but it has the advantage of not being damaged because it is not made of glass, and the use of any material for the window plate The advantage is that you can choose.

The sample can be introduced into this cell in the same manner as the glass cell shown in FIG. 1, and can be handled in the same manner when an accurate cell length is desired. Moreover, the cell can be easily washed.

In order to obtain an accurate cell length, as in the case of the glass cell shown in FIG.
It may be inserted between them, or may be adjusted by using the piezoelectric actuator 32 and the uniaxial pulse stage 33 as shown in FIG.

Next, the stainless steel cell shown in FIG. 6 (the window plates 103 and 115 are made of ZnSe)
FIG. 7 shows the result of the measurement using the product (Made in Japan). The sample is milk.

The measurement procedure is as follows.

(A) In the apparatus shown in FIG. 5, a stainless cell is fixed to the cell holder 31.

(B) The inner cylinder 111 is pulled by the uniaxial pulse stage 33 to suck the sample.

(C) The inner cylinder 111 is pushed to push the excess sample out of the cell.

(D) The computer 35 controls the movement of the uniaxial pulse stage 33, and stops when it has moved by a constant value.

If the cell length is in the micron order, the window plates 103 and 115 are in a close contact state. A liquid film is generated between the window plates 103 and 115.

(E) The piezoelectric actuator 32 controls the pressure to be constant.

The result of spectrum scanning in this state is shown in FIG.
The interference pitch due to the optical path difference between cell lengths is superimposed on the absorption spectrum of this milk sample.

From this interference pitch, the current cell length can be calculated by the computer. If the calculated value is smaller than the specified cell length, the pressure is weakened, and if the calculated value is conversely, the pressure is increased and feedback is performed to set an accurate predetermined cell length.

(F) When the correct cell length is set, the sample is spectrally scanned.

(G) When the spectrum scan is completed, insert the current sample into the inner cylinder.
Discharge by operation of 111 or external pump.

(H) When performing continuous measurement, take the next sample and perform the measurement.

Note that the interference pattern of the spectrum is too strong, which may cause a measurement error. In that case, the P-polarized light can be removed by making it incident on the cell surface at Brewster's angle (see JP-A-60-224002).

In addition, the sample may adhere to the cell surface and cause a measurement error. In that case, the error can be removed by obtaining the difference between the absorbance measurement values at the two cell lengths (see Japanese Patent Application No. 1-16584).

The above is the measurement example using the scanning spectrum.

Next, an example of measuring the liquid component concentration in the optical system device using the interference filter 46 will be described with reference to FIG.
The coarse movement means (uniaxial pulse stage) 33 shown in FIG.
The fine movement means (piezoelectric actuator) 32 and the fine movement means 32 are shown as movement means 53 in FIG.

In this device, the light emitted from the light source 41 is reflected by the reflection mirror 42.
After being reflected by, the light is focused on the cylinder variable length cell 43 of the present invention. The sample 44 is flown into a cylinder type variable length cell. The light that has passed through the sample is reflected by the reflection mirror 45 and then transmitted through the interference filter 46 to be dispersed. The disk 47 has six interference filters 46 of different wavelengths attached, and rotates 15 times per second. The wavelength of the interference filter is a characteristic absorption wavelength related to the component to be measured, a wavelength that is not directly related to the component to be measured, but has a correlation between the characteristic absorption of the solvent and the concentration of the component to be measured due to the interaction with the solvent, and , Wavelength, which is related to the physical properties of the solution such as scattering degree, color, etc. The wavelength used may be in the ultraviolet to infrared range. The transmitted light is a reflection mirror
After being reflected by 48, it is focused on the sensor 49. Sensor
49 converts an optical signal into an electric signal. Computer 51
Separates an electric signal (measurement value) from the sensor 49 into signals of 6 wavelengths corresponding to the interference filters 46, converts the signals into digital values by AD conversion, and obtains a transmitted light amount value I of each wavelength.
The computer 51 also performs cell length control described in detail below.

(1) The absorbance data at the infrared wavelength where the optimum cell length is in the region of several 100 μm is measured as follows. The optimum cell length is the length of the cell in which the absorbance A of the target sample is 0.1 to 1.

First, the relationship between the absorbance A obtained by subtracting the error due to absorption, scattering, and reflection of the cell itself and the voltage V for the fine movement of the moving means 53 is obtained. Therefore, the solvent (for example, water) of the sample to be measured is caused to flow into a cylinder-type variable length cell having a cell length of about 10 mm in advance, and the cell length is set to, for example, 500 μm by the coarse movement moving means. Next, the optimum cell length is several hundreds
If the interference filter a (λ = 1.93 μm) having a wavelength in the range of several μm and that does not change depending on the component concentration of the sample to be measured is selected and the fine movement voltage V of the cylinder (and therefore the cell length) is changed to measure the absorbance A, The data shown in Figure 9 were obtained. (The increasing direction of V is the decreasing direction of the cell length.)
Since the absorbance A and the cell length are proportional to each other according to Beer-Lambert's law, it should be possible to determine the cell length from the absorbance data, but in reality there is absorption, scattering, and reflection of the cell itself, so the absorbance data shows that amount. The data obtained by subtracting the absorbance of is proportional to the cell length. The absorbance component due to absorption, scattering, and reflection of the cell itself was 0.20 as a converged value of the graph when the fine movement voltage V in the graph of FIG. 9 was set to infinity by extrapolation calculation. The proportional coefficient between the absorbance data and the cell length can be determined by measuring the absorption coefficient of water.
It was 70 / μm.

Further, the cell length may be obtained by obtaining the relationship between the fine movement voltage V and the absorbance differential data dA / dV at the voltage V from the graph of FIG. Before the cell window plates are close to each other, the amount of change in the absorbance (= the amount of change in the cell length) with respect to a constant increase in the fine movement voltage V (in the case of the piezoelectric element type actuator) is constant. Therefore, dA / dV has a constant value, but when the cell window plates come close to each other, the −dA / dV value decreases due to the internal stress of the sample liquid. Its value is mainly a function of the cell length at that time. The relationship between dA / dV and cell length is
Obtained in advance and used in subsequent measurements.

The relationship between this fine movement voltage and the accompanying variation in cell length is
It is almost the same even if the cell length due to the coarse movement is different. If desired, the cell length due to the coarse movement may be changed for measurement.

(2) Next, the sample is measured.

The cell length is set to 500 μm by the coarse movement moving means.

The amount of transmitted light is changed by using the light from the interference filters b, c, d, and e with the wavelengths corresponding to the optimum cell length of several hundreds of μm, and changing the two cell lengths (for example, 300 μm and 200 μm) by the fine movement moving means. To measure.

Let Ib ₁ , Ic ₁ , Id ₁ , and Ie ₁ be the amounts of transmitted light when the cell length is 300 μm.

The amounts of transmitted light when the cell length is 200 μm are Ib ₂ , Ic ₂ , Id ₂ , and Ie ₂ .

The difference absorbance data ΔAb is calculated from Ib ₁ and Ib ₂ by the following formula.

ΔAb = −LOG (Ib ₁ / Ib ₂ ) Similarly obtain ΔAc, ΔAd, ΔAe.

As shown in Japanese Patent Application No. 1-16584, this differential absorbance data eliminates stains on the cell surface, scattering, and errors due to reflected light due to the difference in refractive index.

Based on the difference absorbance data ΔAb, ΔAc, ΔAd, ΔAe, C (concentration of the component to be obtained) is determined from a calibration curve formula of C = f (ΔAb, ΔAc, ...).

The calibration curve formula is obtained by measuring a large number of known samples in advance and determining it from the C and the measurement data ΔAb, ΔAc ...

3) Although the case where the optimum cell length is in the region of several hundred μm has been described above, the same measurement can be performed when the optimum cell length is in the region of several μm.

When the optimum cell length is several 10 mm or several mm, it is not necessary to correct the cell length by the fine movement moving means.

When measuring the same sample with various cell lengths, it is preferable to sequentially move from the longer cell length side to the shorter cell length side.

(Effect of the Invention) In the cylinder type variable length cell according to the present invention, the cell length (the distance between the window plate portion of the outer cylinder and the window plate portion of the inner cylinder) can be adjusted in the order of microns. Also, find the actual cell length,
Based on this, the cell length can be adjusted more accurately on the order of microns.

[Brief description of drawings]

FIG. 1 is a sectional view of a cylinder type variable length cell. FIG. 2 is a cross-sectional view of the cylinder type variable length cell of FIG. 1 in which the inner cylinder is pulled out. FIG. 3 is a sectional view of a cylinder type variable length cell in which a ring is inserted. FIG. 4 is a cross-sectional view of a cylinder type variable length cell in which a cell length having a constant thickness is maintained by a ring. FIG. 5 is a diagram of a cylinder-type variable-length cell kept at a constant thickness by using a uniaxial pulse stage and a piezoelectric actuator. FIG. 6 is a sectional view of a stainless steel cylinder type variable length cell. FIG. 7 is a graph of an example of measurement of absorbance. FIG. 8 is a diagram of an example of a device using a cylinder type variable length cell. FIG. 9 is a graph of fine movement voltage and absorbance. 1 ... Outer tube, 2 ... Tube section, 3 ... Window plate section, 11 ... Inner tube,
12 …… Cylinder part, 13 …… Window plate part, 32 …… Piezoelectric actuator, 33 …… One-axis pulse stage.

Claims (3)

[Claims] 1. An outer cylinder having one end face open and a window plate portion on the other end face, and a window plate portion parallel to the window plate portion of the outer cylinder on one end face. An inner cylinder that is inserted into the inner cylinder and is movable in the axial direction, a branch pipe for injecting and discharging a sample between the window plate part of the outer cylinder and the window plate part of the inner cylinder, and a holding means for holding the outer cylinder. In a state where the window plates of the outer cylinder and the inner cylinder are in close contact with each other, a fine movement moving means for moving the inner cylinder inserted in the outer cylinder in the axial direction, and the inner cylinder inserted in the outer cylinder in the axial direction, The actual cell length of the cell length of the sample between the coarse movement means capable of moving a distance longer than the fine movement means can move and the window plate part of the outer cylinder and the window plate part of the inner cylinder. Cell length control means for changing the cell length by controlling the cell length control amounts of the coarse movement movement means and the fine movement movement means based on the measured value. Cylindrical length cell to. 2. The cylinder-type variable length cell according to claim 1, wherein the same sample is used as a window plate portion of the inner cylinder in a state where there is almost no temperature change of the sample between the inner cylinder and the outer cylinder. The relational expression between the absorbance and the cell length is obtained in advance by measuring the absorbance and the cell length of the sample when light is transmitted through the sample held between the window plate of the inner cylinder and the above cell length control. Cylinder type variable length cell, characterized in that the means controls the movement amount of the inner cylinder by the fine movement moving means on the basis of the measured value of the cell length of the sample between both window plate portions and the above relational expression. 3. The cylinder type variable length cell according to claim 1 or 2, wherein the fine movement moving means comprises a piezoelectric actuator, and the coarse movement moving means comprises a pulse stage using a pulse motor. A cylinder type variable length cell characterized by the following.