CN101140221A - Method and polarimeter for measuring optical right and left rotation direction - Google Patents
Method and polarimeter for measuring optical right and left rotation direction Download PDFInfo
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- CN101140221A CN101140221A CNA2007101340922A CN200710134092A CN101140221A CN 101140221 A CN101140221 A CN 101140221A CN A2007101340922 A CNA2007101340922 A CN A2007101340922A CN 200710134092 A CN200710134092 A CN 200710134092A CN 101140221 A CN101140221 A CN 101140221A
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Abstract
The invention relates to a method for measuring left and right rotary directions of optical rotation; a sample tube measured in the optical path adopts a step type sample tube, the length ratio of the sample tube is an irrational number, the sample tube is place in the same optical path formed by a polaroid and a half-shade plate or three-shade plate, the optical line after each sample tube is detected by an analyzer after the liquid transmission in the step type sample tube, and the length of two steps of sample pipes is respectively a and b; in the measuring process, the indicated number x<SUB>a</SUB> and x<SUB>b</ SUB> measured by the analyzer is substituted into the upper left formula to determine the integer m<SUB>a</SUB> and m<SUB>b</SUB>, and two satisfiable formulas and get T<SUB>a</SUB> and T<SUB>b</ SUB>, namely the T in the following specific rotation formula is substituted into the upper right formula to get the value of [alpha<SUP>1</SUP>]<SUB>D</SUB><SUP>t</SUP>. The invention can realize the purpose of determining the left and right rotary directions of the optical rotation through one-time measurement and simple calculation.
Description
Technical Field
The invention relates to a physical optical detection method and a physical optical detection device, in particular to a method for distinguishing left and right rotation directions of optical rotation and an polarimeter
Background
Optical rotation is an essential characteristic of some crystalline, pharmaceutical, etc. substances. When the molecular structure of a crystal or an organic compound is asymmetric, the plane of vibration of light polarized by a plane can be rotated by a certain angle, that is, the substance has optical activity. The optical rotation angle measurement is a commonly used measurement method in optical physics, and has wide application in the aspects of material structure research, chemical substance identification, food and drug component measurement and the like. Since polarimeter technology cannot meet all application requirements, various improvement methods are emerging continuously, and the original polarimeter system is improved respectively from the aspects of mechanical performance (see the Chinese patent application 200520040576.7), reading mode, detection signals and optical path design (see the Chinese patent 93226203.1, measurement of the optical rotation angle of chiral substances by a double optical path method, rivalvine, panxuefeng, pottery defender, kummer, optical instruments, volume 28, phase 6, chinese patent 01143888.6) and the like.
When linearly polarized light passes through a certain substance, the vibration plane of the polarized light rotates by a certain angle alpha, and the phenomenon is called optical rotation phenomenon. A substance that can rotate a linearly polarized light oscillation plane by an angle α of rotation or an optical rotation is called an optical rotation substance. Facing the light source, if the optically active substance rotates the vibration plane of the polarized light in a counterclockwise direction, it is called a left-handed substance. Conversely, if the vibration plane of polarized light rotates clockwise, it is called "right-handed substance". A polarimeter is an instrument that measures the optical rotation of a substance. The specific optical rotation [ alpha ] is commonly used because the optical rotation of each substance depends on its structure, concentration, temperature at the time of measurement, wavelength of light used, and thickness of the liquid layer through which polarized light passes] λ t The optical rotation of each compound is shown. After the optical rotation is measured by the polarimeter, the specific optical rotation of the optically active substance solution can be calculated according to the following formula,
wherein, alpha is the optical rotation observed in the experiment, namely the rotation angle of a polarization detector in the polarimeter; l is the length of the optical tube in dm; c is the concentration of the optically active substance, expressed as mass (g) of the sample contained per 100mL of the solution; t is the ambient temperature (. Degree. C.) at the time of measurement; λ is the wavelength of light, usually sodium yellow light (with a common average value of 589.3nm for its wavelength), marked with D, i.e. written as [ α ]] D t . And the specific optical rotation [ alpha ] of the solute is usually determined by the optical rotation alpha when polarized light is passed through a solution containing 1g of an optically active substance per ml of a non-optically active solvent to a depth of 1dm]. Such as the polarimeter WZZ-2 type automatic polarimeter commonly used at present.
The method and the instrument for detecting by using the polarimeter have the following defects: the existing polarimeter has an inherent defect in measuring the optical rotation, namely, a measurement result can only statically inform the final polarization direction of polarized light after the polarized light is deflected by a sample tube, but cannot provide dynamic process information, namely, the rotation direction of the polarized light in the sample tube cannot be distinguished. In other words, when the reading on the polarimeter is rotated rightwards by 60 °, it is directly rotated rightwards by 60 ° or rotated leftwards by 120 ° or 300 °; when the polarized light reaches the polarization analyzing prism crystal D, the polarized light can not rotate for several circles, and the number of revolutions is determined; is we to consider this material not optically active (chiral)?
In view of the above problems, the prior art discloses certain measures to solve. The method usually employed is to take at least one more measurement with solutions of different concentrations or with sample tubes of different lengths. If the first time the dial reads + 60. After a 1/2 reduction in concentration or a 1/2 shortening of the sample tube, a reading of 60 °/2=30 °; if the concentration is-120 degrees, the concentration is reduced by 1/2 or the sample tube is shortened by 1/2, and the reading is-120 degrees/2 = -60 degrees. This allows distinguishing between two possible optical rotation directions and optical rotations. However, the disadvantages of this approach are also apparent: the measurement needs to be carried out at least twice under different conditions, which wastes samples and is easy to produceGenerating errors; more importantly, this method does not fundamentally solve the problemResolution of optically active beams: according to this method, the two cases of +60 ° and-120 ° can be clearly distinguished, but the difference between the two cases of +60 ° and-300 ° cannot be known. Obviously, this improvement method is incomplete. Taking the actual situation as an example, suppose that at a certain acidity, starch is prepared separately
Quinine, quinine
And L-aminopropionic acid
Standard solution (1 g solute per ml aqueous solution). In a 1dm long sample tube, the optical rotations of the three solutions were measured to be shown as right-handed 16 ° (new chemical tables, respecting the celebration, first edition of 8 months 1998). By using the above-mentioned modified method, the optical rotation of the three solutions was measured to be-82 °, and 8 °, respectively, by diluting the three solutions to 1/2 concentration or replacing with a 1/2 length of sample tube. Thus, the L-aminopropionic acid can be identified from the three substances, but the further identification of starch and quinine can be realized only by further diluting the solution, replacing a sample tube or changing a detection method. In this way, although the principle of the conventional improvement method is simple and easy to understand, the conventional improvement method is inconvenient in actual operation, and measurement errors are introduced when the experimental device is diluted and replaced for multiple times, so that the accuracy of the experiment is influenced.
An improved method (WXG-4 type disk polarimeter, lijun, king Security, johnson, proc education college (comprehensive edition), vol.18, no. 4) has also been proposed by Lijun et al, who changed the sample tube of the conventional polarimeter into a freely contractible piston-type sample tube to complete the work of measuring the optical rotation of the substance at one time. However, the piston mentioned in the article needs good light transmission and sealing performance, which brings great difficulty in processing a new sample tube; in addition, due to the expansion and contraction of the piston, a large amount of liquid can flow into the funnel, and the funnel in design is directly contacted with air, so that most of the liquid is exposed in the air, the optical rotation of an air-sensitive substance is not easy to measure, and a sample chamber is easy to stain.
Disclosure of Invention
The invention aims at: a method for distinguishing left and right rotation directions of optical rotation and an polarimeter are provided, aiming at the defects of the original polarimeter and the defects of the first improved methods, the new method provided by the inventor is used for reconstructing a sample tube on the basis of the original polarimeter, and a new sample tube structure is designed. The method can successfully solve the problem that the optical rotation direction cannot be distinguished.
The purpose of the invention is realized as follows: the method comprises the steps of adopting step-shaped sample tubes, wherein the length ratio of the sample tubes is an irrational number and an approximate irrational number, placing the sample tubes into the same optical path constructed by a polaroid and a half-shadow plate (a triple-shadow plate), detecting the light behind each sample tube by an analyzer after the liquid of the step-shaped sample tubes is transmitted, the length of the second-order sample tubes is a and b respectively,
during the measurement, the index x measured by the analyzer is measured a ，x b Into the formula
Finding two integers m satisfying formula a ，m b Then, T can be obtained a And T b I.e. T in the following specific rotation formula
The method introduces the combination of the semi-transparent mirror and the plane reflector in the polarimeter, can measure samples with different lengths at one time under the condition of the same light source, and reduces the influence of different light sources on the measurement parallelism.
The device of the invention: a polarimeter for distinguishing left and right rotation directions of optical rotation comprises a sample tube, a polaroid, a light path constructed by a half-shadow plate or a three-shadow plate and an analyzer, wherein the sample tube adopts a step-shaped sample tube, the length ratio of the sample tube is an irrational number and a value approximate to the irrational number, the sample tube is placed in the same light path constructed by the polaroid and the half-shadow plate (the three-shadow plate), and light rays behind each sample tube are detected by the analyzer after the light rays are transmitted by liquid of the step-shaped sample tube. In particular, the light source forms a parallel light path through the semi-transparent mirror and the plane reflector, and the parallel light path is provided with the polaroid, the semi-shadow plate, a branch pipe of the stepped sample tube and the analyzer. The ratio of the length of the sample tube is an irrational number, an approximate irrational number, which refers to a number holding the two-digit decimal of an irrational number or a fraction holding the two-digit decimal of an irrational number.
The invention has the beneficial effects that: the object of the invention can be achieved by one measurement and a little calculation. The invention adopts a step-shaped sample box, and the steps are generally two-step, but can be multi-step, and only the light path is simply changed. The per-step length ratio of the sample tube is an irrational, or near-irrational, step tube length. Compared with the traditional method, the method can solve the problem of left and right optical rotation superposition, and the required measurement work can be completed at one time, so the operation is simple and convenient. Particularly for some materials sensitive to air, the problems of long-time contact deterioration of the sample and the air and the like possibly caused by the existing method are avoided. The light path is also relatively simple and is easy to apply in the actual measurement process.
Drawings
FIG. 1 is a schematic diagram of a polarimeter
FIG. 2 is a schematic view of the apparatus of the present invention
FIG. 3 is a schematic diagram of the optical path of the present invention
In the figure: a monochromatic light source 1, unpolarized light 2, a polarizer or polarizing plate 3, plane polarized light 4, a semi-shadow plate 5, two-part plane polarized light 6, a sample tube 7, a stepped sample tube 8, an analyzer 9, a laser light source 10, a semi-transparent mirror 11, and a plane reflector 12
Detailed Description
As shown in fig. 2 and 3, the sample tube is firstly changed into a step shape, and the improved sample tube can simultaneously detect samples with different lengths, so that the possibility of human errors is reduced;
the optical path shown in fig. 3 will be described in detail below. The light emitted from the laser source is divided into two beams by the semi-transparent semi-reflecting mirror, and the two parallel beams pass through the polaroid and the semi-shadow plate respectively and are emitted into the sample tube from the upper part and the lower part of the stepped sample tube. The light incident from the upper part of the sample tube is called #1 light, and the corresponding light incident from the lower part is called #2 light. Because the lengths of the upper part and the lower part of the stepped sample tube are different, the deflection degrees of the #1 polarized light and the #2 polarized light are different, so that the deflection degrees of the light detected by the two analyzers are different. In general, the degree of deflection is considered to be proportional to the length of the sample tube, and we can calculate the optical rotation of the sample by measuring the degree of deflection of the #1 and #2 polarized light.
Calculation of the length of the newly added quartz tube (sample tube):
in the method of the present invention, the concept of the step-shaped sample tube is provided, but the step parameter is not provided in the above, and the method for obtaining the key parameter is provided as follows:
now, the right hand is positive. In the upper part of the stepped tube, the two possible rotation angles of the polarized light are respectively a rotation T a 1° And rotation of T a 2° Let its common index be x a If two different hypothetical conditions are met, the light rays after passing through the a-tube are coincident:
wherein m is a 1 ，m a 2 Are all integers. The deflection angle of the #2 ray through the b-tube can be written relative to the case of the #1 ray through the a-tube:
similarly, m b 1 ，m b 2 Are all integers, x b 1 ，x b 2 Are separately readings of the polarimeter for two different hypothetical cases. And #1The situation of the light is different, and if the two light beams are separated by the #2 light beam, the deflection of the #2 light beam must satisfy the condition:
because a linear relation exists between the optical rotation and the thickness of the optical rotation medium, the following results are obtained:
the relation is then obtained:
the formula is obtained by the theorem of sum ratio:
order to
And is obtained from (6)
(s is an integer) and bringing back (13) to give:
since l and s are integers of arbitrary values, it can be concluded that the b/a value satisfying the condition is only possible to be an irrational number. For example: \58286and the like,
and the like.
After the conclusion is reached, in the measuring process, only the measured indication number x is needed a ，x b Into the formula
Two integers m satisfying the formula (15) are obtained a ，m b Then, T can be obtained a And T b Bring back
Formula (ii) can be obtained 1 ] D t The value of (c).
The simplest sample tube of 1: 58286 (i.e. the ratio of the parameters a and b of the stepped sample tube is:
the length of the tube a is still 1dm, and the length of the tube b is \58286/dm) compared with that adopted in the conventional method
The measurement methods of (a) were compared, and the three samples described above were tested with this apparatus.
The following table lists the measured data:
TABLE 1 data record table for distinguishing starch, quinine and L-aminopropionic acid solutions according to the method of the invention (1: 58286; sample tube)
| #1 actual | Detector | 1 | # | 2 actual | Detector | 2 readings | m a | m b | |
| Starch Quinine (quinine) L-aminopropionic acid | 196 16 -164 | 16 16 16 | 276.36 22.56 -231.24 | -83.64 22.56 -51.24 | 1 0 -1 | 2 0 -1 |
Table 2 prior art method (length ratio of
Two independent sample tubes) data record table for distinguishing starch, quinine and L-amino propionic acid solutions
| First measurement Actual deflection angle | First measurement Detector reading | First measurement Actual deflection angle | First measurement Detector reading | m a | m b | |
| Starch Quinine (quinine) L-aminopropionic acid | 196 16 -164 | 16 16 16 | 98 8 -82 | -82 8 -82 | / / / | / / / |
From the data in the above table, it can be seen that in the case of the new method where the detector 1 is unable to resolve the three solutions, the data collected at the detector 2 indicates that the three substance solutions are significantly different. M is to a ，m b The specific optical rotation of the three substances can be obtained by substituting the value of (2) into the formula (1):
starch
Quinine (quinine)
L-aminopropionic acid
The conventional method cannot distinguish between starch and L-alanine solution. And after the new method is adopted, the solutions of the three substances can be distinguished only by one-time measurement, the experiment operation is simple, convenient and rapid, and the side reaction caused by long-time exposure of the solution in the air and unnecessary liquid flow is avoided.
It should be noted that, due to the limitation of accuracy in actual work, a sample tube with an irrational number ratio in the true sense is difficult to manufacture, but a sample tube with an approximate irrational number can meet most measurement requirements, and generally adopts a value with a two-digit decimal number or adopts an irrational number with a two-digit decimal number to meet practical requirements, mainly for convenient calculation. Therefore, the sample tube without the rational number ratio is only an ideal conceptual mode, and in practical work, the measurement and identification can be achieved only by applying an approximate form of the sample tube. Therefore, the approximate irrational number means a number holding a two-digit decimal number of an irrational number or a fraction holding a two-digit decimal number of an irrational number has a practical effect.
Claims (5)
1. A method for measuring left and right rotation directions of optical rotation is characterized in that a step-shaped sample tube is adopted as a sample tube for optical path measurement, the length proportion of the sample tube is an irrational number, the sample tube is placed in the same optical path constructed by a polaroid and a half-shadow plate or a three-shadow plate, light rays behind each sample tube are detected by an analyzer after liquid transmission of the step-shaped sample tube, the lengths of the second-order sample tube are a and b respectively,
during the measurement, the index x measured by the analyzer is measured a ，x b Substituted into the formula
Finding two integers m satisfying the formula a ，m b Then, T can be obtained a And T b I.e. T in the following specific rotation formula
2. The method of claim 1, wherein the polarimeter incorporates a combination of a semi-transparent mirror and a plane mirror to perform one measurement of samples of different lengths under the same light source.
3. The method of claim 1, wherein the step-type sample tube is used as a sample tube for optical path measurement, and the sample tube is a second-order sample tube having lengths of a and b, respectively, and having b/a values of 58286,
irrational number of (1).
4. The polarimeter for measuring left and right rotation directions of optical rotation comprises a sample tube, an optical path constructed by a polaroid and a half-shadow plate or a three-shadow plate and an analyzer, and is characterized in that the sample tube adopts a step-shaped sample tube, the length ratio of the sample tube is an irrational number, the sample tube is placed in the same optical path constructed by the polaroid and the half-shadow plate or the three-shadow plate, and light rays behind each sample tube are detected by the analyzer after being transmitted by liquid of the step-shaped sample tube. In particular, the light source forms a parallel light path through the semi-transparent mirror and the plane reflector, and the parallel light path is provided with the polaroid, the semi-shadow plate, a branch pipe of the stepped sample tube and the analyzer.
5. A polarimeter according to claim 4, wherein the sample cell to be measured in the optical path is a stepped sample cell, and the lengths of the stepped sample cell are a and b.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103987316A (en) * | 2011-12-19 | 2014-08-13 | 索尼公司 | Measurement device, measurement method, program, and recording medium |
| CN105628623A (en) * | 2015-12-25 | 2016-06-01 | 北京市农林科学院 | Method for identifying optical rotation of optical isocompound |
| CN109596576A (en) * | 2017-09-30 | 2019-04-09 | 清华大学 | Nanometer light field spin-orbit interaction measuring system and method |
| CN115060659A (en) * | 2022-08-18 | 2022-09-16 | 天津大学 | Optical rotation angle measuring method based on proportional method and rapid digital phase-locked demodulation algorithm |
-
2007
- 2007-10-19 CN CN200710134092A patent/CN100588952C/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103987316A (en) * | 2011-12-19 | 2014-08-13 | 索尼公司 | Measurement device, measurement method, program, and recording medium |
| CN105628623A (en) * | 2015-12-25 | 2016-06-01 | 北京市农林科学院 | Method for identifying optical rotation of optical isocompound |
| CN105628623B (en) * | 2015-12-25 | 2018-08-24 | 北京市农林科学院 | A method of differentiating optical siomerism chemical combination object optical activity |
| CN109596576A (en) * | 2017-09-30 | 2019-04-09 | 清华大学 | Nanometer light field spin-orbit interaction measuring system and method |
| CN109596576B (en) * | 2017-09-30 | 2020-07-14 | 清华大学 | System and method for measuring nano optical field spin-orbit interaction |
| CN115060659A (en) * | 2022-08-18 | 2022-09-16 | 天津大学 | Optical rotation angle measuring method based on proportional method and rapid digital phase-locked demodulation algorithm |
| CN115060659B (en) * | 2022-08-18 | 2022-10-25 | 天津大学 | Optical rotation angle measuring method based on proportional method and fast digital phase-locked demodulation algorithm |
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