JPH0464058A - Measuring method of molecular weight - Google Patents

Abstract

PURPOSE:To improve the precision in measurement by setting the start point and the end point of a peak of measured data on the basis of corrected linear functions on the macromolecule side and the low molecule side. CONSTITUTION:A GPC(gel permeation chromatograph) device 2 executes a GPC processing for a sample and supplies GPC data thus obtained to a computer 3. Based on a display in a display device 5 thereof, an operator sets arbitrary two points in regions before and behind the rise of a peak of GPC (macromolecule and low molecule sides) and determines linear functions on the macromolecule and low molecule sides (an approximation formula of a GPC curve) from the coordinates of these points. The computer 3 determines a base line connecting two points set at the opposite ends, determines the largest distance (peak height) thereof from the part of the peak of the GPC curve and multiplies this by a prescribed noise compensation value, so that a compensation value be obtained. The start point and the end point of the peak are set on the basis of corrected linear functions on the macromolecule and low molecule sides obtained by adding this compensation value to the above linear functions on the macromolecule and low molecule sides.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for measuring molecular weight, and particularly to a method for measuring molecular weight suitable for use in gel permeation chromatography (hereinafter referred to as GPC).

[Conventional technology]

In recent years, containers made of resin, which is a polymeric material, have been frequently used as containers filled with foodstuffs and the like. This type of container is required to have high reliability in terms of quality, and for this reason, characteristic tests are generally performed on the polymeric material from which the container is made. As one of these characteristic tests, a test to measure the molecular weight of polymeric materials is conducted. In polymer materials, various properties such as strength, impact resistance, and reactivity are closely related to molecular weight.
Therefore, measuring the molecular weight of polymeric materials is more important than maintaining the quality of containers.

GPC (Get
Permeation Chromatography
y) I'm often irritated. According to this GPC, since the sample appears as data starting from components with large molecular weights, it is suitable for measuring the molecular weight of polymeric materials.

FIG. 4 shows measurement data obtained by GPC (the horizontal axis shows time, and the vertical axis shows the number of molecules present).

A conventional molecular weight measurement method for measuring the molecular weight of a sample from this measurement data will be described below.

Measurement data obtained by GPC generally has one or more vertices, and the molecular weight of a sample can be determined by analyzing the curve shape shown by the data. Specifically, the point at which the peak rises (referred to as the starting point) and the point at which the peak completely falls (referred to as the end point) are found, and the line segment connecting this starting point and the ending point (indicated by arrow A in the figure) and the above Curve of measurement data (
The molecular weight of the sample can be determined by calculating the area surrounded by (indicated by arrow B in the figure).

Therefore, it is important to set the above starting point and ending point appropriately.
It is important for molecular weight measurement by C.

Conventionally, the following methods have been used to find the starting point and ending point. Note that since the method for determining the starting point and the ending point is the same, for convenience of explanation, only the method for determining the starting point will be explained.

Here, in FIG. 5, the part circled by an arrow C and circled in FIG. 4 is shown enlarged. As shown in the figure, the measured data is not a smooth curve, but has a linear shape with complicated unevenness due to noise. To find the starting point of this measurement data curve, first, band lines d1 and d2 having a predetermined range are set. This band line d
The widths of i and d2 are arbitrarily set by the operator who operates the data processing machine, and these widths are approximately the same as or slightly larger than the maximum width of the unevenness of the measured data curve. It is set as follows.

Therefore, the value of the measurement data is on this band line d1. d2
If it is within the range of , there is no peak starting point. Therefore,
Based on this, the data processor selects the band line d1 for which the measurement data value has been set. When it is at d2, no starting point is set.

However, the value of the measured data is below this band line di, d.
Even if the point exceeds the range of 2, that point cannot be immediately set as the starting point. This is because the value of the measured data momentarily falls below the band line dl due to measurement errors or disturbances that occur when performing GPC.

This is because the range of d2 may be exceeded.

Therefore, in addition to the start point detection operation using the band line described above, a start point detection method called the tanθ scheme method is used. As shown in FIG. 6, this tanθ scheme method uses the amount of change (ΔV
), and calculate this rate of change (Δt/ΔV: i.e. tanθ)
is larger than a predetermined set value and continues for a predetermined number of times, the starting point at which the rate of change becomes large (indicated by an arrow in the figure)
This is a method of determining that this is the starting point of a peak. Also in this method, the predetermined setting value is a value arbitrarily set by the operator of the data processing machine.

As described above, in conventional GPC automatic data analysis, the molecular weight of a sample is generally measured using band line and jan theta scheme methods. Another method is to artificially set two points in a no-signal region that is not included in the peak, and simply draw a tangential straight baseline.

[Invention or problem to be solved]

In GPC, since the molecular weight of the sample is large, if the starting point and ending point of the peak are not set accurately, the error will be very large and the accuracy of molecular weight measurement will deteriorate.

However, as described above, in the conventional molecular weight measuring method, there are several parameters that must be set by the operator of the data processing machine, and these parameters can be set arbitrarily by the operator. For this reason, there are individual differences in the above-mentioned setting values set by the operator, which causes variations in the settings of the peak start point and end point, and the problem is that only highly accurate molecular weight measurement is possible. was there.

In particular, when the peak height H of the measurement data is high as shown in FIG. 7(A), the band line d1. Even if there is a slight error in the setting width of d2 due to individual differences, the value of this error is small compared to the peak height H, so it is possible to detect the starting point and ending point relatively accurately. B)
As shown in , if the peak height H of the measurement data is low, the band line d1. It becomes difficult to set d2, and large variations occur in the set positions of the starting point and the ending point. For this reason, there is a problem in that the measurement accuracy deteriorates particularly when the peak height H of the measurement data is low.

The present invention has been made in view of the above points, and an object of the present invention is to provide a molecular weight measuring method that improves measurement accuracy by setting the starting point and ending point of a peak at appropriate positions taking into account the maximum peak height. With the goal.

[Means to solve the problem]

In order to solve the above problems, the method of the present invention uses gel permeation chromatography (GPC) of the measured sample.
) into a computer, and draw the region before the GPC peak rises (polymer side region) and the region after the GPC peak falls (low molecule side region) if no sample was injected. Appropriate 2 on wax curve
Set a point, find the polymer side straight line function and the low molecule side linear function connecting these two points, then calculate the peak height from the above GPC, and adjust the above polymer side straight line according to the size of this peak height. Correct the function and the low molecule side linear function, set the point where the above corrected corrected high molecule side straight line function intersects with the GPC curve as the starting point of the peak, and the point where the above corrected low molecule side linear function intersects with the GPC curve. is the end point of the peak, and the molecular weight of the sample is measured by summing the molecular abundance derived from the segmented area for each minute interval on the time axis between the start point and the end point.

[Effect]

According to the above molecular weight measuring method, it is possible to set the starting point and end point of the peak based on the corrected polymer side linear function and the corrected low molecule side linear function.

The corrected polymer-side linear function and corrected low-molecule side linear function are calculated using the coordinates of two arbitrary points set in the polymer side region and the low molecule side region, respectively, and the peak height of the peak of the GPC curve as parameters. Desired. Of these two parameters, the two points set in the high molecule side region and the low molecule side region are set in order to obtain the high molecule side linear function and the low molecule side linear function. Each of these linear functions is a function that approximately represents the baseline in the GPC curve in each region on the polymer side and low molecule side, so even if there are variations due to individual differences when setting these two points, This does not significantly affect the accuracy of molecular weight measurement.

In addition, the other parameter, the peak height, is
This is the value that appears on the GPC curve at the time C is imported into the computer. This peak height is determined by the computer
This is a value automatically taken in from the PC curve, and is not a value set by the operator. Therefore, the peak height is not affected by individual differences.

Further, the starting point and the ending point are determined as the points where the corrected polymer side straight line function and the corrected low molecule side straight line function intersect with the GPC curve. The corrected polymer side linear function and corrected low molecule side linear function are obtained by correcting the above-mentioned polymer side linear function and low molecule side linear function in correspondence with the magnitude of the peak height. Therefore, by finding the starting point and ending point using the corrected polymer-side linear function and corrected low-molecule side linear function, it is possible to improve the accuracy of setting the starting point and ending point.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 shows a molecular weight measuring device 1 used to carry out the method of the present invention. Molecular weight measuring device 1 is GPC device t2,
It is composed of a computer 3 and a printer 4.

GPC outfit! 2 performs GPC processing on the sample, and the measurement data (pJ, below, how to use this data as GPC data)
is supplied to the computer 3. At this time, the GPC data supplied from the GPC device 2 is not supplied to the computer 3 sequentially, but is supplied to the computer 3 after sampling all the data. Alternatively, the data may be sequentially sampled by the computer 3 and then stored in the computer 3.

Now, from the GPC device 2, the GPC as shown in FIG.
Assuming that the data is supplied to computer 3,
A method for determining the starting point and ending point from this GPC data and measuring the molecular weight will be explained.

When GPC data is supplied from the GPC device 2 to the computer 3, the GPC data is displayed on the display device 5 of the computer 3. While looking at this display, the operator of computer 3 first calculates the region before the GPC peak rise (polymer side region) and after the GPC peak falls in order to obtain the polymer side linear function and the low molecule side linear function. Two arbitrary points are set in each region (low molecular side region). Here, the polymer region refers to the region in front of the starting point, the low molecular region refers to the region behind the ending point, and the peak refers to the region between the starting point and the ending point. In addition, G.P.
In C, the components with larger molecular weights of the injected sample elute faster, so the polymer side appears first as data. Therefore, the polymer side is located to the left in the figure, and the low molecule side is located to the right in the figure.

As shown in the figure, (t+, h+) in the polymer region.

(t2. h2) and in the low molecular region (tz, h3)
, (t4.h4) are set. From the coordinates of each point, a linear function on the polymer side and a linear function on the low molecule side are determined.

The polymer-side linear function and the low-molecular-side linear function are equations that approximate GPC curves (referring to graph curves depicting GPC data) in the high-molecular region and the low-molecular region. Therefore, when setting each of the above points, it is necessary to select the point that can best approximate the GPC curve. Therefore, it is not desirable to set the two points too close together, and the coordinates of each point do not necessarily need to be selected on the GPC curve. Furthermore,
The number of points is not limited to two, and a plurality of points may be set in each area.

The polymer-side linear function and the low-molecular-side linear function are determined by the following equations.

*High-molecular-side linear function Ys = AHXt+BH...■ Furthermore, in the above equation, AM = (h+-h2)/(t+-tz) *Low-molecular-side linear function YL=ALxt+BL...■ Furthermore, above In the formula, AL = (hs-ha)/(t, -t,) As mentioned above, the formulas shown by ■ and ■ above are formulas that approximate the GPC curve, so each point set is Doesn't require precision. Therefore, even if the above settings are made by the operator,
Accordingly, individual differences do not affect the measurement results.

Further, the equations indicated by ■ and ■ above are indicated by dashed lines with arrows Y, YL in FIG. 1, and are also displayed on the display device 5.

Once the polymer side linear function and the low molecule side linear function are determined as described above, each equation is corrected.

This correction processing is a feature of the method of the present invention. This correction process is actually executed by program processing of the computer 3.

The computer 3 has the above-mentioned (t+, h+), (L
h2), (ti, h3), (it, h<), < t+, h+) set at both ends,
A straight line connecting (b, h4) (hereinafter referred to as the baseline) is determined, and the distance between this baseline and the peak portion of the GPC curve or the furthest distance (indicated by arrow H in the figure, this is referred to as the peak height) is determined. Next, this peak height H
is multiplied by a predetermined noise compensation value P (%) to obtain a compensation value (D=HxP).

The compensation value obtained here is a value that changes depending on the peak height maximum value H, and is a value that increases as the peak height H increases and decreases as the peak height H decreases. Further, the noise compensation value P is a value predetermined depending on the type of sample whose molecular weight is to be measured.
The noise compensation value is defined based on the noise of the output when the detector inside is stable and no material is being detected. This value is set, for example, to about 1%. The compensation value obtained in this way is added as a correction value to the polymer side linear function (2) and the low molecular side linear function (2) to obtain the corrected polymer side linear function and the corrected low molecule side linear function. Each of these functional expressions is expressed as shown below.

*Corrected polymer side linear function Y) 1-1 = A) l
P *Corrected low molecule side linear function YL-1=AL The equation is indicated by the solid line indicated by the arrow YH-++YL-1 in FIG. 1, and is also displayed on the display device 5.

Here, the part surrounded by O shown by arrow E in Fig. 1 is
It is shown enlarged in the figure. As shown in the figure, the GPC curve contains noise and has irregularities. Moreover, the polymer side linear function Y is shifted upward by the compensation value due to the correction.

This shift amount D (compensation value D) is configured to have a value larger than the maximum value of noise occurring in the GPC music by reflecting the noise compensation value P in the compensation value. Therefore, the value of GPC data exceeds the noise range mentioned above.
There is no starting point before the formula YHY shown by
There is no end point before taking a value less than or equal to L-1. That is, G.P.C.
The starting point is the point where the curve intersects with the formula Y□-1, and the ending point is the point where the GPC curve intersects with the formula YL-1.

In addition, the above shift amount D (compensation value D) is a value that incorporates the peak height H, so as mentioned above, the larger the peak height H is, the larger it is, and conversely, the smaller the peak height H is, the smaller the diameter is. value. Therefore, even if GPC data having various peak heights H as shown in Fig. 7 is input, the compensation value is set to a value corresponding to this, so the starting point and ending point can be set appropriately and accurately. You can set it. This effect is particularly noticeable in GPC data with small peak heights H.

Based on the above-mentioned principle, the computer 3 sets the point where the corrected polymer side linear function and GPC data intersect as a starting point, and the point where the corrected low molecule side linear function and GPC data intersect as an end point. When setting this starting point and ending point, the computer 3
The operator sets (tt, h+), (tt,
h2), (tz, ha), and (t4h4), and all other parameter settings are performed by program processing of the computer 3. Therefore, variations due to individual differences among operators have little effect on measured values, and highly accurate molecular weight measurements can be performed.

When the starting point and the ending point are set as described above, the computer 3 performs an integral process in the range between the starting point and the ending point based on the GPC data function F (t) indicating the GPC curve, and calculates the molecular weight. Note that the integration process for determining the molecular weight is the same as in the conventional method.

〔Effect of the invention〕

As described above, according to the present invention, molecular weight measurement can be performed regardless of individual differences among computer operators, and appropriate correction can be made in accordance with the peak height value when setting the starting point and ending point. It has the advantage of being able to perform highly accurate molecular weight measurements.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the measurement principle of the method for measuring molecular weight according to the present invention, FIG. 2 is an enlarged view of the part indicated by arrow E in FIG. 1, and FIG. FIG. 4 is a diagram for explaining an example of a conventional molecular weight measurement method. FIG. 5 is an enlarged view of the portion indicated by arrow C in FIG. 4. , FIG. 6 is a diagram for explaining the tanθ scheme method, and FIG. 7 is a diagram for explaining errors in molecular weight measurement caused by differences in peak height. 1... Molecular weight measuring device, 2... GPC device, 3...
- Computer, 5...Display device. same

Claims (1)

[Claims] A gel permeation chromatograph (GPC) of a measured sample is imported into a computer, and the region before the peak rise of the GPC (polymer side region) and the region after the peak fall of the GPC are analyzed. (Low molecule side region), set two appropriate points on the curve that would be drawn if there was no sample injection, find the polymer side linear function and the low molecule side linear function that connect the two points, Next, the peak height is determined from the GPC, and the polymer side linear function and the low molecule side linear function are corrected according to the size of the peak height, and the corrected polymer side linear function is the GPC curve. The point where it intersects is the starting point of the peak, and the point where the corrected small molecule linear function corrected above intersects with the GPC curve is the end point of the peak, and from the segmented area of the minute interval area on the time axis between the above starting point and the ending point. A method for measuring molecular weight, characterized in that the molecular weight of a sample is measured by summing the amount of induced molecules present.