JPS6339863B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a packing material for chromatography,
More particularly, the present invention relates to a packing material for organic solvent-based high-speed gel permeation chromatography that has a calibration curve that can be used for separation analysis over a wide range of molecular weights. Gel permeation chromatography (hereinafter referred to as GPC) uses a packing material (hereinafter referred to as gel).
Using the principle that components with a molecular size smaller than the pore size in the gel penetrate into the gel according to their size, and components with a larger molecular size pass through the outside of the gel, It is a type of liquid chromatography that sequentially separates and elutes components. Analysis by GPC is usually performed using a calibration curve. A calibration curve is obtained by plotting the measurement data of a standard sample of known molecular weight on a graph with the logarithm of the molecular weight on the vertical axis and the elution volume on the horizontal axis, and is a straight line with a negative slope or a smooth curve. .
The longer the negative slope part of the calibration curve is and the closer it is to a straight line, the easier and more accurate analysis of a sample of a polymer compound with a wide molecular weight distribution or a sample containing components with widely different molecular weights becomes possible. For example, when measuring molecular weight distribution, the elution curve of a sample must be converted into a molecular weight distribution curve using a calibration curve. The accuracy of the conversion will vary. In other words, when the gradient is extremely steep, there is virtually no separation between the analyte components based on the difference in molecular weight.
The accuracy of molecular weight distribution measurement becomes extremely poor. Therefore, for samples with a wide molecular weight range,
For GPC analysis, it is preferable to use a column packed with a gel that has an appropriate slope and a calibration curve that is close to a straight line over a wide range. However, conventional calibration curves for gels with large pores used for analysis of polymeric compounds have a gentle slope in the high molecular weight region and a steep slope in the low molecular weight region, creating an overall curve. For this reason, such gels cannot be used alone for measuring molecular weight distribution or analyzing high molecular compounds containing low molecular weight components. Therefore, in order to obtain a calibration curve with a long linear region, conventional methods have been used, such as mixing several types of gels with different pore diameters and packing them into a column, or connecting several types of packed columns with different calibration curves in series. was. However, even with these methods, the calibration curve is not completely linear, and because several types of gels or packed columns are combined, it is difficult to always obtain a constant calibration curve. Furthermore, when several types of packed columns are connected together, not only does the analysis take a long time, but the separation performance decreases as the columns are connected, and the separation performance is not always commensurate with the length of the column. There were problems such as not being able to obtain the required amount. The present inventors conducted extensive research to solve the problems of the prior art, and as a result, they discovered a gel that has a calibration curve that is close to a straight line and has an appropriate slope over a wide range of molecular weights. That is, the present invention provides (i) monovinyl aromatic monomer 10
a monomer mixture of ~70% by weight and 30-90% by weight of polyvinyl aromatic monomer, (ii) an organic solvent that dissolves polystyrene in an amount of 50-300% by weight based on the monomer mixture; (iii) 1.5 to 3% by weight of polystyrene based on the mixture of the monomer and the organic solvent; and (iv)
Monovinyl aromatic monomer units and polyvinyl aromatic monomer units are obtained by suspension polymerizing a mixture containing a radical polymerization initiator in water and extracting polystyrene from the resulting granular copolymer. A packing material for chromatography consisting of an aggregate of particles having substantially the same chemical and physical structure as the main skeleton, and which has an exclusion limit molecular weight of 2×10 ⁶ for polystyrene in gel permeation chromatography. ~1×10 ⁸ , and the slope α of the calibration curve is at least 10 ² to 10 ⁶
In the molecular weight range of logM _lin ≦α≦10＋logM _lin and 1≦=α _Max /α _Mio ≦2 (However, in the above formula, α _Max and α _Mio are the maximum value and minimum value of α within the above molecular weight range, respectively. and M _lin is the exclusion limit molecular weight). The skeleton of the gel of the present invention is mainly composed of units derived from monovinyl aromatic monomers and polyvinyl aromatic monomers. Examples of monovinyl aromatic monomers include one or a combination of two or more of styrene, α-methylstyrene, methylvinylbenzene, and ethylvinylbenzene, with styrene and ethylvinylbenzene being preferred. Examples of polyvinyl aromatic monomers include divinylbenzene and trivinylbenzene, with divinylbenzene being preferred. The proportion of polyvinyl aromatic monomer units in the skeleton is preferably in the range of 30 to 90% by weight. If the proportion of the polyvinyl aromatic monomer unit is less than this range, a gel with a large exclusion limit molecular weight and sufficiently high mechanical strength cannot be obtained. Further, since highly pure polyvinyl aromatic monomers are easily polymerized and difficult to handle, those containing a considerable amount of monovinyl aromatic monomers are usually used. For example, commercially available divinylbenzene contains 50 to 60% pure divinylbenzene.
Contains ethylvinylbenzene in addition to weight percent. Although it is possible to obtain a product with higher purity, it is not necessarily preferable because it becomes difficult to handle. Therefore, from a practical standpoint, the proportion of the polyvinyl aromatic monomer unit is preferably in the range of 30 to 60% by weight. The gel of the present invention consists of a collection of particles that are substantially identical in chemical and physical structure. The chemical structure here refers to the type and quantitative ratio of monomer units forming the skeleton, and can be determined by measuring the infrared absorption spectrum. If the relative intensity and position of each absorption in the infrared absorption spectrum are substantially the same for all particles, the particles can be regarded as a collection of particles with substantially the same chemical structure. In addition, the physical structure refers to the pore size, pore size distribution, or pore volume of micropores within the particle, and can be known from the GPC calibration curve. In other words, the molecular weight scaled on the vertical axis of the calibration curve is considered to be a measure of the pore size of the gel, and the pore volume within the gel can be determined from the elution volume plotted on the horizontal axis. Therefore, if all particles have the same GPC calibration curve, they can be regarded as a collection of particles with the same physical structure. However, as a practical matter, it is difficult to obtain a calibration curve for a single particle. A simple and practical way to determine the identity of a particle's physical structure is to observe the surface condition of the particle using a high-magnification microscope. Generally, gels made using exactly the same synthetic conditions such as the type, amount, and formulation of raw materials are considered to be an aggregate of particles with substantially the same chemical and physical structure. Furthermore, when the gel of the present invention is used as a gel for GPC, the exclusion limit molecular weight of polystyrene is 2×10 ⁶
It must be in the range of ~1× ¹⁰⁸ . The exclusion limit molecular weight here refers to the lower limit molecular weight of molecules that cannot enter the pores of the gel, and components with molecular weights greater than this value have substantially the same elution capacity and cannot be separated. Therefore, GPC analysis is usually performed on components whose molecular weight is below the exclusion limit of the gel.
Many of the industrially used polymer compounds have a wide molecular weight distribution, and the high molecular weight side contains components with a molecular weight of nearly 10 ⁶ . The GPC gel used for analysis or molecular weight distribution measurement of such substances preferably has an exclusion limit molecular weight of 2×10 ⁶ or more. The exclusion limit molecular weight is determined from the calibration curve. The calibration curve is a line obtained by plotting the logarithm of the molecular weight of polystyrene on the vertical axis and the elution volume (Ve) on the horizontal axis. represents the relationship between A calibration curve usually consists of a line parallel to the vertical axis followed by a straight line with a negative slope or a smooth curve. The exclusion limit molecular weight in the present invention is expressed as the value on the vertical axis at the intersection of an extension of a line parallel to the vertical axis and an extension of a line having a negative slope.
For gels with a significantly high exclusion limit molecular weight, there is no standard polystyrene with a high molecular weight, so a line parallel to the vertical axis cannot be drawn, and the exclusion limit molecular weight may not be accurately determined. In such a case, the molecular weight exclusion limit should be estimated from the position of a line parallel to the vertical axis of the gel with the lower molecular weight exclusion limit. In the present invention, the calibration curve should be determined using standard polystyrene and benzene that simultaneously satisfy at least the following conditions (a) and (b). (a) Standard polystyrene with M _w /M _N <1.2 (M _W : weight average molecular weight, M _N : number average molecular weight), (b) Any molecular weight of 10 ⁿ to 10 ⁿ⁺¹ (2≦n<6) One or more standard polystyrenes with different molecular weights are used. If there are too few types of standard polystyrene used for measurement, an accurate calibration curve cannot be obtained. The slope α of the calibration curve is the slope of the adjacent actual measurement 2 on the calibration curve.
Connect the points with a straight line and find α _ij for each straight line using the following formula (1): α _ij = |logM _i −logM _j /V _Ri −V _Rj /V _T | (1) M _i , M _j : Standard polystyrene or Molecular weight of benzene, V _Ri , V _Rj : Elution capacity of polystyrene with molecular weights M _i and M _j respectively, V _T : Vacant volume of column, and α _ijk obtained by the following formula (2) is α in the present invention. . α = α _ijk = α _ij + α _jk /2 (2) When calculating α _ij , the difference in elution volume (V _Ri − V _Rj ) is divided by the column volume to eliminate the influence of column size. be. α of the gel of the present invention must be within the range of formula (3) below. logM _lin ≦α≦10＋logM _lin (3) Gels with α smaller than this range and satisfying other properties required for the gel of the present invention will have insufficient mechanical strength, and if α is too large, they will separate. Performance deteriorates, making them unsuitable as packing materials for high performance liquid chromatography. From a practical standpoint, α is more preferably within the range of formula (4) below. 1+logM _lin ≦α≦9+logM _lin (4) Furthermore, the calibration curve of the gel of the present invention has good linearity in the sloped portion. In other words, the ratio of the maximum value of α (α _Max ) to the minimum value of α (α _Mio ) in the sloped part is at least
It is necessary that the molecular weight falls within the range of formula (5) below in the molecular weight range of 10 ² to 10 ⁶ . 1≦α _Max /α _Mio ≦2 (5) If the value of α _Max /α _Mio is larger than 2, the difference in separation performance between steep and gentle slopes becomes too large, so the 10 This is not preferred since the entire molecular weight range of ² to ¹⁰⁶ cannot be used for separation or analysis. The exclusion limit molecular weight and the slope α of the calibration curve are both physical property values specific to the gel, but the flow rate at the time of measurement,
The exclusion limit molecular weight and α of the present invention were obtained by the method described above from the calibration curve measured under the following conditions to ensure accuracy, as they may be affected to some extent by the column shape, combination with solvent and solute, etc. be the value given. Column: Stainless steel, inner diameter 7-8 mm and length 50-60 cm Solvent: Chloroform or tetrahydrofuran Sample: 0.5% polystyrene solution and benzene Flow rate: 0.1-2.0 ml/min Temperature: Room temperature Detection method: UV 254 nm Gel of the present invention Average particle size (hereinafter referred to as _W )
is usually in the range of 1 to 50 μm, preferably 2 to 30 μm. If _W is smaller than this range,
_W
If is too large, the separation performance will deteriorate, which is not preferable. _W is measured by a Coulter Counter (Coulter Electronics, USA) and is determined by equation (6), where n is the frequency at which the particle diameter d appears. _W = Σnd ⁴ /Σnd ³ Next, a typical method for producing the gel of the present invention will be explained.
The gel of the present invention contains (i) 10 to 70 monovinyl aromatic monomers;
% by weight and a mixture of 30 to 90% by weight of polyvinyl aromatic monomer, (ii) 50 to 90% by weight relative to said monomer mixture;
organic solvent that dissolves 300% by weight polystyrene;
(iii) suspension polymerization in water of a mixed solution containing 1.5 to 3% by weight of polystyrene and a radical polymerization initiator based on the mixture of the monomer and the organic solvent;
It can be obtained by extracting polystyrene from the produced particulate copolymer. Here, the monovinyl aromatic monomer is styrene, α
- One or a combination of two or more selected from methylstyrene, methylvinylbenzene, and ethylvinylbenzene, with styrene and ethylvinylbenzene being preferred. The polyvinyl aromatic monomer is selected from divinylbenzene and trivinylbenzene. Among them, divinylbenzene is convenient because it is easy to obtain. The proportion of polyvinyl aromatic monomer in the total monomer is
It is preferably in the range of 30 to 90% by weight. However, commercially available divinylbenzene usually consists of about 60% by weight of pure divinylbenzene and about 40% by weight of ethylvinylbenzene, and higher purity ones are not generally used because they are difficult to manufacture and handle. Therefore, it is convenient to use the polyvinyl aromatic monomer in a proportion of 30 to 60% by weight. Here, monomers other than divinylbenzene, such as ethylvinylbenzene, contained in commercially available divinylbenzene are calculated as monovinyl aromatic monomers. If the proportion of the polyvinyl aromatic monomer in the total monomers is less than 30% by weight, a gel with a high exclusion limit molecular weight and high mechanical strength cannot be obtained. An organic solvent that dissolves polystyrene means an organic solvent that dissolves linear polystyrene having a weight average molecular weight of 10 ⁴ to 10 ⁶ at room temperature in an amount of 1% by weight or more,
Such a solvent is selected from aromatic hydrocarbons, ketones, esters, and nitriles, and specifically, benzene, toluene, xylene, cyclohexanone, methyl benzoate, butyl acetate, etc. are preferred.
Among them, toluene is particularly preferred. These solvents may be used alone or in any combination of two or more. The solvent is used in an amount of 50 to 300% by weight based on the total amount of monovinyl aromatic monomer and polyvinyl aromatic monomer. If the amount of solvent is less than this range, the pore volume of the gel will decrease and the separation performance will deteriorate; if it is too much, the mechanical strength of the gel will decrease, making the gel unsuitable for high-speed GPC. From a practical point of view, the amount of solvent is
Preferably it is in the range of 100-200% by weight. The polystyrene added to the polymerization solution preferably has a weight average molecular weight in the range of 10 ⁴ to 10 ⁶ . The amount of polystyrene added to the polymerization solution is preferably in the range of 1.5 to 3% by weight based on the total amount of the monomer and the organic solvent capable of dissolving the polystyrene.
The amount of polystyrene significantly affects the shape of the calibration curve. If the amount of polystyrene is less than the above range, the gel will have a low exclusion limit molecular weight, and if it is more than the above range, the calibration curve will become curved and the linear region will become short, which is not preferable. Radical polymerization initiators include azo initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile), and peroxides such as benzoyl peroxide and lauroyl peroxide. Commonly used initiators such as oxide initiators can be used, and there are no particular limitations. The amount of initiator used is within the range normally used in suspension polymerization of styrene, for example from 0.1 to 5.0% by weight based on the total monomers. The suspension stabilizer added to the aqueous phase is selected from commonly known organic polymer stabilizers such as polyvinyl alcohol and methyl cellulose. The volume ratio or weight ratio of the organic phase to the aqueous phase during polymerization is not particularly limited, and may be within a range normally selected when carrying out suspension polymerization. The gel of the present invention has a conventional exclusion limit molecular weight of 10 ⁶
As described above, compared to a high-speed GPC gel consisting of an aggregate of particles having substantially the same chemical and physical structure, the gel has a calibration curve that is close to a straight line in a wide molecular weight range of 10 ² to 10 ⁶ or more. Therefore, samples with a wide molecular weight range or mixtures of samples can be analyzed using a column packed with one type of gel.
Figure 1 shows the calibration curve of the gel of the present invention synthesized in Example 1, and Figure 2 shows the elution curve obtained by analyzing standard polystyrene mixed samples with different molecular weights in a column packed with this gel. It is something that In addition, Figure 4 shows the calibration curve of a commercially available packed column HSG-60 (Shimadzu Corporation), and Figure 5 shows the calibration curve obtained by using that column to measure the same sample used for the measurement in Figure 2. This figure shows the elution curve. The gel in this commercially available column has a styrene-divinylbenzene skeleton similar to the gel of the present invention, but the slope of the calibration curve becomes steep on the molecular weight side lower than 10 ⁴ , so the molecular weight is 1.02×10 ⁴ , 2.8× 10 ³ and
The mutual separation of 4.7×10 ² standard polystyrene is not good. On the other hand, the calibration curve of the gel of the present invention is almost linear in the molecular weight range of 10 ² to 10 ⁶ or more, so the standard sample, which was not well separated with the commercially available gel, was also well separated. There is. The gel of the present invention has a calibration curve that is close to a straight line in such a wide molecular weight range, but as mentioned above, conventionally, in order to obtain such a calibration curve, various gels with different calibration curves were suitably used. It was necessary to use a column packed with a mixture of However, even in a column packed with a mixture of several types of gels, the linearity of the calibration curve was not as good as the gel of the present invention. Furthermore, since several types of gels are mixed, a high degree of reproducibility is required for the physical properties of each gel and the filling state, making it difficult to always obtain a constant calibration curve. On the other hand, if the gel of the present invention is used, it is only necessary to use one type of gel, and therefore a calibration curve with a long linear region can be obtained easily and with good reproducibility. Hereinafter, the present invention will be explained in more detail with reference to Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples. Example 1 60 g of commercially available divinylbenzene (56% purity, most of the rest being ethylvinylbenzene), 120 g of toluene
g, 4.2 g of polystyrene with a weight average molecular weight of 2 x 10 ⁵
(2.3% based on the total amount of monomer and toluene) and 1.6 g of 2,2'-azobisisobutyronitrile, and 0.6 weight of polyvinyl alcohol (degree of polymerization 2400, saponification rate 90%) Water containing %1520
ml into two round bottom flasks. While the outside of the flask was cooled in an ice-water bath, the inside of the flask was stirred at about 20,000 rpm for 60 minutes using a lab disperser. Next, place the flask in a water bath kept at 80°C.
Stir the inside of the flask with a boat-shaped bladed stirring rod to 80℃.
was heated for 10 hours to polymerize. The obtained polymer particles were separated, thoroughly washed with water and acetone in that order, and then dispersed in acetone for simple classification using the difference in sedimentation rate. Furthermore, the particles were extracted with tetrahydrofuran and then dried to obtain a gel. The average particle size of the gel was measured in an isotone solution using a Coulter Counter Model ZB (Coulter Electronics, Inc., USA) and was found to be 9.5 μm. This gel was dispersed in chloroform and filled in an upward flow into a stainless steel column with an inner diameter of 7.5 mm and a length of 50 cm, and a chloroform solution of standard polystyrene with a known molecular weight was measured to obtain the results shown in Table 1. Furthermore, this result was plotted on a graph to obtain the calibration curve shown in FIG. From this calibration curve, the exclusion limit molecular weight is estimated to be approximately 8 x 10 ⁶ , which is equal to benzene (molecular weight 78) and molecular weight 4.48.
α _Max is 11.55 between ×10 ⁶ standard polystyrene;
α _Mio was 9.01 and α _Max /α _Mio was 1.28. molecular weight
4.48×10 ⁶ , 1.26×10 ⁶ , 4.22×10 ⁵ , 1.86×10 ⁵ ,
When a mixed sample containing 4.28×10 ⁴ , 1.02×10 ⁴ , 2.8×10 ³ and 4.7×10 ² polystyrene was analyzed using this packed column, each polystyrene was well separated as shown in FIG. The relationship between the peak number in FIG. 2 and the polystyrene molecular weight is as follows. Peak No. Molecular weight 1 4.48×10 ⁶ 2 1.26×10 ⁶ 3 4.22×10 ^{5 4} 1.86×10 ⁵ 5 4.28×10 ⁴ 6 1.02×10 ⁴ 7 2.8×10 ³ 8 4.7×10 ²

[Table] Example 2 Styrene 25.7g, divinylbenzene (purity 56
%, the majority of the rest being ethylvinylbenzene) 65.3
A homogeneous liquid mixture consisting of 90 g of toluene, 4.6 g of polystyrene with a weight average molecular weight of 2 x 10 ⁵ (2.6% based on the total amount of monomer and toluene), and 2.4 g of 2,2'-azobisisobutyronitrile. Polymerization, washing, and
A gel was obtained by separation and drying. The average particle size of the gel was 9.2 μm. Disperse this gel in chloroform and use an upward flow to create an inner diameter of 7.5 mm.
A chloroform solution of standard polystyrene with a known molecular weight was measured by filling a stainless steel column with a length of 50 cm, and the results shown in Table 2 were obtained. Furthermore, this result was plotted on a graph to obtain the calibration curve shown in FIG. From this calibration curve, the exclusion limit molecular weight is estimated to be approximately 7×10 ⁶ , and between benzene and standard polystyrene with a molecular weight of 4.48×10 ⁶ , α _Max is 15.18, α _Mio is 10.30, and α _Max /α _Mio is
It was 1.47.

[Table] Comparative Example 1 A commercially available column (Shimadzu HSG-60,
Standard polystyrene (inner diameter 8 mm, length 50 cm) was measured in chloroform solvent to obtain the measurement results shown in Table 1 and the calibration curve shown in FIG. The exclusion limit molecular weight determined from the calibration curve is approximately 7×10 ⁶ and the molecular weight is 4.48.
At ×10 ⁶ or less, α _Max was 87.45, α _Mio was 5.30, and therefore α _Max /α _Mio was 16.5. Comparing the calibration curve in Figure 4 with the calibration curve for the gel of the present invention, there are few parts that can be considered a straight line, and the slope becomes extremely steep at molecular weights below ¹⁰⁴ , indicating that the separation performance is low in this region. can be predicted. When a mixed sample of the same standard polystyrene as in Example 1 was analyzed using this packed column, an elution curve as shown in FIG. 5 was obtained. Comparing FIG. 5 with FIG. 2 of Example 1, the molecular weights are 1.02×10 ⁴ , 2.8×10 ³ and 4.7×
It can be seen that the standard samples of 10 ² are poorly separated from each other and are not suitable for analyzing samples containing components with widely different molecular weights.

[Table] Comparative Example 2 All the same as Example 1 except that 1.8 g (1.0% based on the total amount of monomer and toluene) of polystyrene with a weight average molecular weight of 2 × 10 ⁵ added during polymerization was used in Example 1. A gel was obtained in the same manner. The average particle size of this gel was 9.3 μm. This gel was packed into a column in the same manner as in Example 1, and standard polystyrene was analyzed to create a calibration curve. The exclusion limit molecular weight of this gel, determined from the obtained calibration curve, was approximately 5×10 ⁵ and was not suitable for analysis of samples containing components with molecular weights around 10 ⁶ . Comparative Example 3 Everything was carried out in the same manner as in Example 1, except that 6.0 g (3.3% based on the total amount of monomer and toluene) of polystyrene with a weight average molecular weight of 2 × 10 ⁵ added during polymerization was used. A gel was obtained. The average particle size of this gel was 9.8 μm. This gel was packed into a column in the same manner as in Example 1, and standard polystyrene was analyzed to create a calibration curve.
And it became as shown in Figure 6. Determined from the calibration curve,
The exclusion limit molecular weight is approximately ¹⁰⁶ , which is slightly lower than the gel of the present invention, and in the molecular weight range of ¹⁰² to ¹⁰⁶ , α _Max is 18.11, α _Mio is 7.40, and α _Max /α _Mio is 2.45.
As a result, the linearity was extremely poor.

[Table] Comparative Example 4 In Example 2, everything was the same as in Example 2 except that 9 g of polystyrene (5.0% based on the total amount of monomer and toluene) with a weight average molecular weight of 2 × 10 ⁵ was added to the polymerization solution. A gel was obtained in the same manner. The average particle size of this gel was 10.1 μm. This gel was packed into a column in the same manner as in Example 2, and a standard polystyrene sample was analyzed to obtain the calibration curve shown in FIG. The exclusion limit molecular weight determined from Figure 7 is approximately
10 ⁶ , which is slightly lower than Example 2, and below M _lin , α _Max is 20.68, α _Mio is 7.06, and α _Max /α _Mio is 2.9.
3
The linearity was also extremely poor.

[Brief explanation of the drawing]

FIG. 1 is a calibration curve obtained using a standard polystyrene chloroform solution for a column packed with the gel obtained in Example 1. FIG. 2 is an elution curve diagram obtained by analyzing a polystyrene mixture of eight different molecular weights as a sample using the packed column of Example 1. FIG. 3 is a calibration curve obtained using a standard polystyrene chloroform solution for a column packed with the gel obtained in Example 2. FIG. 4 is a calibration curve obtained for the commercially available gel-filled column of Comparative Example 1 using a standard polystyrene chloroform solution. FIG. 5 is an elution curve diagram obtained by analyzing the polystyrene mixture sample used in Example 1 using the packed column of Comparative Example 1. FIG. 6 is a calibration curve obtained using a standard polystyrene chloroform solution for a column packed with the gel obtained in Comparative Example 3. FIG. 7 is a calibration curve obtained using a standard polystyrene chloroform solution for a column packed with the gel obtained in Comparative Example 4.

Claims (1)

[Scope of Claims] 1 (i) a monomer mixture of 10 to 70% by weight of monovinyl aromatic monomer and 30 to 90% by weight of polyvinyl aromatic monomer, (ii) based on the monomer mixture 50 to 300% by weight of an organic solvent that dissolves polystyrene; (iii) 1.5 to 300% by weight of the mixture of said monomer and said organic solvent;
A monovinyl aromatic monomer unit obtained by suspension polymerizing a mixture containing 3% by weight of polystyrene and (iv) a radical polymerization initiator in water and extracting polystyrene from the resulting granular copolymer. A packing material for chromatography consisting of an aggregate of particles having substantially the same chemical and physical structure, with a main skeleton of polyvinyl aromatic monomer units, and polystyrene used in gel permeation chromatography. the exclusion limit molecular weight is within the range of 2×10 ⁶ to 1×10 ⁸ , and the slope α of the calibration curve is at least log Mlim≦α≦10+log Mlim in the molecular weight range of 10 ² to 10 ⁶ , and 1≦αMax /αMin≦2 (where αMax and αMin represent the maximum and minimum values of α within the molecular weight range, respectively,
A packing material for chromatography characterized by having a molecular weight within the range of