CS213917B1 - Silica gel sorbent for chromatography in ionizing and aggressive environments - Google Patents

Abstract

The invention relates to a silica gel sorbent for chromatography in ionizing and aggressive environments. The sorbent consists of a silica gel matrix, which is covered with a layer of highly cross-linked, possibly partially or completely carbonized poly(acrylonitrile). It has high radiation resistance and chemical stability to acids. It enables chromatographic analysis of radiopharmaceuticals and analytical determination of rare emitters.

Description

The invention relates to a silica gel sorbent for chromatography in ionizing and aggressive media.

Currently, silica gel as the basic sorbent is most commonly used for modern high pressure liquid chromatography methods (Knox J. H., editor of High-Performance Liquid Chromatography, Edinburgh Univ. Press). The possibility of producing it in the form of accurately spherical particles with variable and controllable pore distribution is very important, and is also one of the reasons for its considerable expansion. Equally important is its mechanical strength, which is required due to the high pressures of the chromatography itself and, in particular, the extreme pressure pulses often used to fill the columns with sorbent. However, the chemical nature of the available sorbent surface on the one hand has a decisive influence on the nature of the chromatographic separation of substances and on the other hand the composition of the mobile phase on the other determines the retention characteristics of the chromatographic separation of the mixture.

The composition and hence the polarity of the mobile phase can be varied without difficulty. The silica gel surface is often modified by chemical reaction with a suitable silanizing agent (Berendsen G.E., Galan L. S. of Liquid Chromatography 1, 561 (1978)). Another way to change the surface properties of silica gel is to impregnate it with a suitable polymer (Wheals B. B. B. J. Chromatography 107,

402 (1975)). Modified sorbents generally satisfy the requirements imposed on them with respect to the desired separation, but they are poorly resistant especially in aggressive or ionizing environments.

In the first case, destruction of bound molecules can occur, in the second case radiation crosslinking or even destruction in both cases results in an undesirable change in sorbent properties. This disadvantage is overcome by the sorbent of the present invention.

The essence of the silica gel sorbent according to the invention is that the surface of the silica gel matrix is coated with a layer of highly crosslinked optionally partially or fully carbonized poly (acrylonitrile).

This material is suitable for chromatography in aggressive and ionizing environments and is essentially a silica gel sorbent with a coating that can be characterized as a polyacxylonitrile coating followed by crosslinking and cyclization under controlled pyrolysis. The resulting sorbent is characterized by high radiation resistance with chemical resistance to acids. At a total dose of? Radiation (Co?) Of 500 M rows, no change in the chromatographic properties of the column packed with the above sorbent was observed, i.e. in the capacity factors and the efficiency of the column. The method of thermal treatment is decisive for the overall chromatographic properties of the material.

The high radiation resistance is due to the presence of a significant number of aromatic rings formed by pyrolysis of poly (acrylonitrile) at higher temperatures (MIiller DJ, Overhoff D. * Angex. Macromol. Chem. 40/41, 423 (1974). Cyclization of poly) acrylic monomer units and

nitrile) starts already when heated to 200 ° C in the presence of oxidizing substances. At higher temperatures; It is necessary to work in an inert atmosphere and the nitrogen is split off and the carbonization is progressive. At temperatures of 700 to 1300 ° C, the pyrolyzed poly (acrylonitrile) contains only 1

up to 0.3% nitrogen. The physico-chemical properties of the pyrolyzed poly (acrylonitrile) such as thermal conductivity, mechanical strength, wettability and hence hydrophobicity are! also dependent on the temperature and pyrolysis time. In our case a wide range of sorbents with different properties can be prepared according to the temperature and length of pyro213 917 lysis. The strongly pyrolyzed sorbents (600 to 1400 ° C) exhibit low wettability with water and are particularly suitable for extraction-chromatographic work. Adsorption chromatography, on the other hand, is a methodology for which such pyrolyzed sorbents are not suitable, since the chromatographic peaks of all standard substances are considerably unsymmetrical. Weakly pyrolyzed sorbents (200 to 400 ° C) have higher water wettability and are useful for liquid adsorption chromatography.

The sorbent is prepared by dispersing pure, stabilized, structured silica gel in a 5-40% solution of poly (acrylonitrile), dimethylformamide, dimethylsulfoxide, and the like. whereupon the excess poly (acrylonitrile) solution is removed e.g. by filtration and the material is dried. The polymer silica can be washed with, for example, acetone to facilitate lump disintegration (not necessary), followed by air drying at 150 to 220 ° C. Even at this temperature, a partial cross-linking of the poly (acrylonitrile) occurs and the polymer stabilizes on the surface of the silica gel. The oxidative crosslinking of the polymer is then further deepened, for example by heating in air at 200 to 300 ° C for 5 to 25 hours, which can be shortened by boiling in aromatic nitro compounds, eg by boiling in nitrobenzene for 2 hours. If we want to hydrophobize the polymer layer by partial or complete carbonization, we heat this product to. temperature of 700 to 1400 ° C in a stream of eg nitrogen. The resulting product must be purified by fractionation, for example on sieves and multiple sedimentation.

Silica gel sorbent with a layer of pyrolyzed poly (aiylonitrile) is particularly suitable for use in radiochemistry, but its further use is not limited. Despite some of the drawbacks that most organic material sorbents have on an inorganic matrix, the pyrolyzed poly (acrylonitrile) layer sorbent is suitable for liquid chromatography in radiochemistry, particularly for its high resistance to ionizing radiation and acids. Ease of production, versatility of use and low price are essential.

The following are examples of sorbent production and its use for analysis of radiopharmaceuticals and analytical determination of rare emitters.

EXAMPLE 1 g of silica gel (produced according to the method of AO No. 200 997) of medium size 12

About jun and spec. The 480 m / g coating was suspended in 50 ml of a freshly prepared 15% solution of poly (acrylonitrile) in dimethylformamide. With stirring, the suspension was boiled for 5 minutes and after cooling the silica gel was separated on a filter. The product was heated in an oven at 210 ° C for 2 hours. After the lumps were comminuted, the sorbent was sieved through a 30 m screen and decanted twice ace a ton. Elemental analysis of the dry product indicated 12.46% C, 4.4% N and 1.0-3% H.

Example 2 g of spherical silica gel (produced according to No. A0 No. 179 184) having an average particle size of 10 µm and spec. A surface of 400 m @ 2 / g was treated as in Example 1. However, after heating to 210 DEG C., the product was suspended in 100 ml of nitrobenzene and heated under reflux for 2 hours. The resulting black beads were then washed on the frit with chloroform and

213 917 with acetone and dried. The product was then heated in a furnace quartz flask for 5 hours at 1000 ° C under a stream of nitrogen. Elemental analysis of the washed and dried product yielded 6.85% C, 1.16% Na 0.27% H.

Example 3

131 ·· 131

Rapid determination of ^J J in ortho ^J -H-hippurane by adsorption chromatography method.

For the determination of the radioisotope of iodine ¹ · ¹ , a 50 mm column with an internal diameter of 2 mm was used with a sorbent prepared according to Example 1 with a poly (acrylonitrile) layer treated at 210 ° C. The sorbent is loaded into the column by a suspension technique in methanol, pressurized and washed with distilled water. In an aqueous medium of 0.111 HNO 3 + 0.1 M NaNO 2 (1 »1) at flow rates of 1-2 ml / min is not captured and is separated from ortho-β-hippurane. Figure 1 shows a typical chromatogram with scintillation detection of ¹ µl, 1 is and 2 is ortho-β-hippuran. This method is very simple and fast, applicable to commercially-controlled 131 control of ortho-J-hippurane and other iodine-labeled 131 and 123-labeled radiopharmaceuticals.

Example 4

Determination Am ² ^ ¹ in admixture with Sr ^ ^0, ^ ¹ ^ C * ² ^ ^8, and U by extraction chromatography.

The sorbent with the poly (acrylonitrile) layer treated according to Example 2 is filled with the suspension technique into polyethylene columns with a maximum dimension of 20 x 2 mm. The sorbent in the column is washed successively with acetone, a 30% solution of di (2-ethylhexyl) phosphoric acid in toluene and 0.1 L of HCl. After these operations the box is ready for use. A sample of 10-10 * 1 is applied to the top of the column and washed successively with 0.111 HCl, 1.5 M HCl and 1211 H01. In fraction of 1.5M H01 is only ² ^ ¹ Am see Fig. 2 which shows the elution pattern of mixtures of americium, cesium, strontium and uranium, with 3 - the activity of A <* - ^ ^{1 2} isotope Am. After washing the column with 0.111 HCl, it is again possible to separate ² µM. 10 separations can be made per column without significantly reducing capacity. After 10 separations, the column is regenerated by washing with acetone, a solution of di (2-ethylhexyl) phosphoric acid in toluene and 0.1 M HCl. ² ^ ¹ in the fraction Am 1511 HC1 was sUwiovuje oc spectrophotometrically after nasorbování naelektrolyzování or dots on ion-exchange or stainless steel. The method of separation is very fast and can be performed without significantly increasing the volume of solution to be analyzed, because the total amount of processed solution of ^2-1 exceeding 100 Am ^ .1.

Claims (1)

SUBJECT OF THE INVENTION Silica gel sorbent for chromatography in ionizing and aggressive media, characterized in that the surface of the silica gel matrix is coated with a layer of highly crosslinked optionally partially or fully carbonized poly (acrylonitrile).