JPS5823577B2 - Polarimeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical rotation needle, and more particularly to an optical rotation needle that determines the optical rotation angle of a sample by periodically vibrating a vibration surface and electrically processing a signal from a detector.

Conventional optical rotation needles or optical rotation dispersion needles use the so-called optical zero position method, rotate the optical rotation angle of the sample according to the optical rotation angle of the sample, and determine the optical rotation angle of the sample from the rotation angle of the analyzer.

However, since this method is a mechanical detection method in which the analyzer is rotated, the accuracy of the obtained optical rotation angle depends on the mechanical accuracy of the analyzer rotation, and is approximately 0.001° at most.
Furthermore, due to the mechanical operation, the response speed is slow, which is an essential drawback.

An object of the present invention is to provide a completely new method of measuring the angle of optical rotation of a sample by electrical processing without using a method of mechanically rotating an analyzer.

In the optical rotation needle of the present invention, there are two ways to electrically process the output from the detector depending on the vibration angle δ of one plane of polarization and the optical rotation angle θ of the sample. ] holds and the approximation formula can be applied, the plane of polarization is oscillated at fHz, and the light after passing through the sample;
While keeping the fHz component signal constant, the fHz component signal is synchronously rectified and the resulting voltage is measured to determine the optical rotation angle of the sample. In this case, the polarization plane is also oscillated at fHz, and the fH contained in the detector output with the sample inserted is
Of the fundamental wave and harmonic signals of z, extract a specific frequency component that includes a phase shift based on the optical rotation angle of the sample, compare it with a standard signal component that is not affected by the optical rotation angle of the sample, and calculate the phase difference between the two. The angle of optical rotation of the sample is determined by the detection.

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

In the figure, dotted lines indicate optical signals, and solid lines indicate electrical signals.

In FIG. 1, light from a ray 1 passes through a lens 2 and becomes parallel rays, and then passes through a filter 3 where it becomes monochromatic light.

This monochromatic light becomes linearly polarized light by polarization 4, and then passes through Faraday cell 5, where the plane of polarization of the linearly polarized light is vibrated at an angle of ±δ radian, a frequency of fHz, and a sine waveform.

6 is an oscillation circuit for causing a sinusoidal current to flow through the coil of the Faraday cell.

After leaving the Faraday cell 5, the linearly polarized light whose polarization plane oscillates passes through the sample 7, passes through the analyzer 8 disposed perpendicular to the polarizer 4, enters the detector 9, and is converted into an electrical signal.

A photomultiplier tube is generally used as the detector 9 (!).

First, polarizer 4 and analyzer 8 are inserted without sample T.
Let them be orthogonal.

Since the plane of polarization is vibrated by the Faraday cell 5 in a sinusoidal waveform with an amplitude of ±δ radian and a period of fHz, the intensity 1 of the light incident on the detector 9 at this time is given by the following equation.

■, == ■ost direct δsin 2πft) where, ■
o is the light intensity incident on the detector when the polarizer and analyzer are parallel, and t is the time in units of seconds.

Next, if we consider a state in which a sample with an optical rotation angle θ is placed, the angle of the vibration plane will deviate by θ, so the intensity of light incident on the detector 9 2 is expressed by the following equation. .

However, T is the transmittance of the sample.

Now, assuming that δ(1, θ(1) holds true, the above 2 can be approximated as follows.

Therefore, if the output from the detector 9 at this time is 2, then k
Assuming that is a constant, it becomes .

Focusing on this equation (2), the first term is the 2 fHz component that does not include the optical rotation angle θ of the sample, and the second term is the fe that includes the first-order θ.
It can be seen that the z component, the third term, is a DC component containing second-order θ.

Therefore, by extracting only the fHz component of the second term, θ can be determined.

However, in 5, since T included in the coefficient is a value that changes depending on the sample, it is necessary to standardize its magnitude.

So, if we look at the above equation again, the same coefficient KT/100 is applied to the first term, so if we keep the size of the 2f component, which is not affected by θ, constant, we can determine the size of the f component. Coefficients can be normalized.

In other words, by first extracting only the 2 fHz component of the output of the detector 9 and controlling the sensitivity of the detector so that the first term becomes a constant, if the fHz component is extracted and synchronously rectified, the 2 fHz component is
It is possible to obtain only normalized information that includes only the first-order θ by cutting out the DC component and the DC component.

Corresponding to the electrical system part in the figure, after the output from the detector 9 passes through the preamplifier 10, only the 2f component is 2fHz.
The signal is amplified by the detector control circuit 1.
2 to automatically control the sensitivity of the detector and keep the 2fHz component constant.

That is, if the sensitivity of the detector is adjusted to 100/KT times, the above (2) can be given by an equation that does not include the variable T.

Reference numeral 13 denotes an fHz amplifier, which increases only the fHz component by 1, and then converts it into a DC signal in the synchronous rectifier circuit 14, which converts the 2fHz component and the first and third terms of the DC component.
The term is cut, and the output from the synchronous rectifier circuit 14 becomes 2.
The size is proportional to 1oδθ.

Therefore, if the value of 2■oδ is calibrated in advance using a sample whose optical rotation angle is known, the optical rotation angle θ of the sample can be determined by measuring ■≦.

Reference numeral 15 is a voltage indicator, and a suitable device such as a voltmeter, recorder, or oscilloscope is used.

Next, if we consider the general case where δ(1, θ(1) does not hold and an approximation formula cannot be used, the equation (2) above can be transformed as follows.

This is the formula for the Bessel function of the first kind, If we apply X2δ and θ22πft to

That is, the exact 2 which is not an approximation of δ(1, θ(1) is given by the above equation.

Expanding this formula yields the following terms.

From the double angle formula of trigonometric functions If you substitute It is expressed as

Here, the first term of 12 represents the DC component and does not include the optical rotation angle θ due to the sample.

The following is a harmonic component whose frequency component is an even multiple of the vibration frequency f of the polarization plane, and its amplitude is AJn2(δ)-, and the phase of each frequency is determined by the optical rotation angle of the sample, when there is no sample. This shows that there is a deviation of 2θ compared to .

In addition, in the second term of ■2, the frequency component includes harmonics of fHz, the amplitude is AJ n (δ) Jm (δ) - (n≠m), and the angle of rotation θ due to the sample is not included. Not there.

In the next example, the frequency component includes harmonics of fHz, the amplitude is A 'J n (δ) J m (δ) - (n≠m), and the phase of each frequency depends on the optical rotation angle θ of the sample. , it shows that there is a shift of 2θ compared to when there is no sample.

Therefore, even in the general case where δ(1, θ(1) does not hold,
Among the fHz fundamental wave and harmonic signals contained in the detector with a sample inserted, a specific frequency component containing a phase shift based on the optical rotation angle of the sample is extracted, and the position of both is determined by comparing it with a standard signal. It is understood that by detecting the phase difference, the angle of optical rotation θ of the sample can be determined.

Next, the detection method will be specifically explained.

FIG. 3 (aXb) shows the values of the Bessel function Jn(δ) with δ and n as parameters, respectively.

Since Jn(δ) defines the respective magnitudes of the fHz fundamental wave and harmonic signals contained in the output from the detector, δ
The size of n determines how many n should be considered.

For example, when δ21, n=0, 1, 2,
3, n larger than that can be ignored, and if we look at Figure 3, we can see that δ (1 has a meaning as shown in the previous approximation), the DC component (n = 0), fHz component (n
=t), 2 fHz component (n=2).

Further, FIG. 4 shows an example of the frequency spectrum distribution based on FIG. 3, in which the absolute value of each frequency component is taken in the case where there is no optical rotation angle θ due to the sample.

■2 is the square of the spectrum in Figure 4, the first term of ■2 means the square of each frequency component itself, and the second term
The term means the product of one frequency component and another frequency component.

Here, since the magnitude of the first term is the square of itself, it is clear that the thickest term is larger than the product of a certain frequency component and another frequency component of the second term.

Therefore, if the vibration angle δ and frequency f are given and the value of n to be considered is determined, select a specific frequency component n, that is 2nf, where Jn(δ) is the largest among them,
By comparing it with a standard signal that does not include a phase shift due to the optical rotation angle θ of the sample, and detecting the phase difference between the two, 2θ can be determined.

FIG. 2 is a block diagram showing a polarimeter using this method.

The same numbers as in FIG. 1 indicate the same parts, and the parts up to the preamplifier 10 are the same as in FIG. 1, so their explanation will be omitted.

After the output of the preamplifier 10 is amplified by the main amplifier 16,
The signal enters a group of filters 17 and is separated into each frequency component.

As mentioned above, among n determined by the size of δ,
The particular frequency component giving the largest amplitude is extracted and entered into phase detector 19.

On the other hand, the signal from the oscillation circuit 6 is used as a standard signal component that does not include the influence of the optical rotation angle of the sample.

This signal passes through a frequency divider 18 and is made to have the same frequency as the above-mentioned specific frequency component, and then similarly enters a phase detector 19.
A phase difference 2θ between both components is detected.

Various methods can be considered for detecting the phase difference in the phase detector 19, and any method is possible.

Further, in the illustrated embodiment, the standard signal component is obtained from the oscillation circuit 6, but a signal portion of the output from the detector that does not include the phase difference due to the optical rotation angle of the sample may be used.

Next, we will show a measurement example in which the present optical spectrometer is combined with high performance liquid chromatography when δ(1, θ<] holds.

Example 1 As a light source, the wavelength is 6328, the output is about 2, the beam diameter is about 0.
An 8'IIL'IIL He-Ne laser was used, and the Faraday cell was oscillated at a frequency of 370 Hz with an amplitude of approximately ±0.5°.

The sample cell is a quartz UV with an inner diameter of 1 m and a length of 10 mm.
A flow cell for the detector was used.

The column was packed with Lichrosorb-NH2 (5 μm) at 250 x 4 mfii-b, and acetonyl-IJ-water was used as the solvent.

The flow rate was 0.8 ml/min, and when each saccharide was analyzed, the results shown in FIG. 5 AB and C were obtained.

Figure 5 A is a standard sample of 200 μg each of fructose 1, glucose 2, and sucrose 3, B is a commercially available soft drink 3
μ6. C shows the measured spectrum when 10 μl of wine was directly injected at a solvent ratio of 75:25, the horizontal axis is time (minutes), and the vertical axis is the optical rotation angle.

Example 2 Under the same conditions as Example 1, glucose 1, maltose 2
, 200 μg each of maltriose 3 in a solvent ratio of 60:40
When the sample was injected, the measured spectrum shown in FIG. 6 was obtained.

Example 3 1. Under the same conditions as Example 1. Arabinose 25°50
．． Volumes of 75.100, 150' and 200 μg were injected and quantitative properties were examined, and as shown in FIG. 7, good linearity was obtained.

Note that the detection limit in this case was 2 μg when the S/N was 2.

Example 4 Amino acids were analyzed using the polarimeter and column under the same conditions as in Example 1, using acetonitrile-0.01M KH2P 04 (solvent ratio 70:30) as the solvent.

The flow rate was 0.8 mA/mino D-tryptophan 100 μg (1), D-leucine 200 μg (2),
D-proline 80 μg (3), D-asparagine 200
When 200 μg (4) and 200 μ9 (5) of D-serine were injected, measurement spectra as shown in FIG. 8 were obtained.

Further, (1') to (5) are measurement results regarding L-form amino acids corresponding to the above (1) to (5), respectively.

゛As described above, according to the present invention, the optical rotation angle of the sample is determined by electrically processing the signal without using mechanical response means, so the response speed is fast and measurement at minute angles is possible. Accuracy is also improved, achieving an accuracy of 0.0001°C.

Furthermore, if a laser is used as a light source and the data is accumulated over a long period of time by a computer, an accuracy of 0.00001° can be achieved.

Furthermore, since no mechanical parts are used, the entire polarimeter can be manufactured at low cost.

In addition, the method of vibrating the plane of polarization is that instead of using the Faraday cell 5, the polarizer 4 or analyzer 8 is oscillated at an angle of ±δ,
It may be measured by vibrating it with a sine waveform of fHz, and of course it is also possible to apply it to an optical rotation dispersion meter.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a polarimeter according to the present invention when δ(, θ(1) holds; FIG. 2 is a block diagram showing a polarimeter according to the present invention when δ(1, θ(1) cannot be approximated.
Figures 3a and b are diagrams showing the values of the Bessel function Jn(δ) with δ and n as parameters respectively, Figure 4 is a diagram showing the frequency spectrum distribution at each value of δ, and Figures 5A, B, and C
, 6, 7, and 8 are diagrams showing measurement results when the polarimeter shown in FIG. 1 was combined with high-performance liquid chromatography, respectively, where the horizontal axis is time (minutes) and the vertical axis is the angle of optical rotation. 1...Light source, 2...Lens, 3...
...filter) 4...polarizer, 5...
・Faraday cell, 6...Oscillation circuit, γ...
...Sample, 8...Analyzer, 9...Detector, 10...Preamplifier, 11...
2 fHz amplifier, 12...detector control circuit, 13... fHz amplifier, 14...
Synchronous rectifier circuit, 15... Voltage indicator, 16...
...Main amplifier, 17...Group of filters, 18
...Division period, 19...Phase detector.

Claims (1)

[Claims] 1. In the optical rotation needle, the plane of polarization is vibrated at fHz, and the output from the detector corresponding to the light after passing through the sample is 2fHzFi.
An optical rotation needle characterized in that the optical rotation angle of a sample is determined by synchronously rectifying the fHz component signal and measuring the voltage while keeping the fHz component signal constant. 2. In the optical rotation needle, the plane of polarization is vibrated at fHz, and among the fHz fundamental wave and harmonic signals included in the detector output with the sample inserted, a specific signal containing a phase shift based on the sample's optical rotation angle is detected. An optical rotation needle characterized in that the optical rotation angle of the sample is determined by extracting a frequency component, comparing it with a standard signal component that is not affected by the optical rotation angle of the sample, and detecting the phase difference between the two.