PL206989B1 - Gas chromatography column packing and method for its manufacture - Google Patents

Description

Description of the invention

The subject of the invention is a packing for gas chromatography in which the surface of the support is chemically modified.

There are known columns for gas chromatography, especially capillary, in which the packing is a porous sorbent such as silica, molecular sieves (zeolites), aluminum oxide, activated carbon and porous polymers [Zhenghua Ji et all, J.Chromatography A, 842 (1999) 115-142; Hao Yun et all (J. Microcol. Sep. 7, 153-158, 1995), US Patent No. 4,293,415]. These fillings are used, among others, in open capillary columns with internal diameters from 100 to 750 μm, with a porous layer of sorbent deposited on the internal wall of a PLOT (Porous-Layer Open-Tubular column) capillary. PLOT columns are produced by depositing a porous, unmodified, sorbent on their inner walls.

In other embodiments, the filling is a transition metal compound chemically bonded to the support surface by an organosilicon compound with complexing properties [W.Wasiak, W. Urbaniak, J. of Chromatography A, 757, 137, (1997)]. The Polish patent specification No. 185095 discloses a solution in which organosilicon derivatives of ketoenamine are used as complexing compounds, obtained by reacting an aminosilane with a β-diketone derivative.

There are also known chromatographic fillings, which are carriers which are modified organosilicon compounds, without complexed transition metal [S. Ahuja "Chiral Separation by Chromatography, Oxfortd University Press., 2000]. However, these are compounds with a very complex chemical structure.

Surprisingly, it turned out that also simple organosilicon compounds modified with ketimine groups applied to the support can be an effective filler for gas chromatography. The essence of the invention, in which the mineral carrier is modified with an organosilicon compound, consists in the fact that the organosilicon compound is a ketimine derivative of the general formula in which R ¹ and R ² are equal or different and represent an alkyl group containing from 1 to 6 carbon atoms in the molecule, n is an integer from 1 to 3, and m is an integer from 1 to 10, and R ³ is an alkyl or aryl group optionally containing at least one optically active carbon atom.

The method of producing a gas chromatographic packing in which the carrier is subjected to a condensation reaction with a silane consists in using an organosilicon derivative of ketimine as the silane of the general formula in which R ¹ , R ² , R ³ , m and n are as defined above.

In the invention, various compounds having free hydroxyl groups, such as silica, porous glasses, aluminum silicates, oxides - for example aluminum, zirconium, titanium - can be used as a carrier.

The silane of the general formula in which R ¹ , R ² , R ³ , m and n are as defined above used in the invention is a compound obtained as a result of a condensation reaction of an organosilicon compound containing a diketone group with a primary amine.

In the invention, a variety of primary amines which react with the carbonyl group of the silane are used to modify the packing properties. Since the range of available amines of this type is very wide, the invention allows to obtain fillings with various properties, shaped by the nature of the organic amine group. The use of optically active amines allows for the preparation of fillings for the separation of optically active compounds, which in the methods known to date is much more technically complicated and depends on the availability of appropriate optically active reagents.

The filling according to the invention is characterized by high thermal stability and resistance to oxidation.

The invention is illustrated by the following examples in which methods for the preparation and use of the fillings according to the invention are shown.

P r z k ł a d I

A. Preparation of silane

15 mmoles of 3- (3-trietoksysililopropyIo) of 2,4-pentanedione was added excess (20 mmol) of tert-butylominy and 10 cm ³ of benzene. It was heated under reflux azeotropically, while the water that was released was collected. The progress of the reaction was monitored by chromatography. After complete conversion of the silane, benzene and excess amine were distilled off, and the product was distilled under reduced pressure. Analysis showed the product to be, 2- (tert-butylamino) -3- (3-triethoxysilylpropyl) pentanone-4.

PL 206 989 B1

Elemental analysis: determined [%]: Si - 7.98, C - 60.09, H - 10.23, N - 3.96 calculated [%]: Si - 7.80, C - 60.17, H - 10.31, N - 3.90;

MS: m / z - 344 [M -15] ⁺ , m / z - 316 [M - 43] ⁺ (ions characteristic for organosilicon compounds are formed as a result of the elimination of methyl and acetyl groups formed from the ethoxy group);

In the IR spectrum, characteristic bands for the carbonyl group: 1734 cm ^-1 (ν CO), and for the imino group 1605 cm ^-1 (ν C = N).

B. Preparation of the filling

3.5 g of silica (Nucleosil, 5 µm granulation, 300 A pore diameter) was dried at 110 ° C under reduced pressure to remove adsorbed water. The dried silica was quenched with dry xylene was added 4.5 cm ^{3 of} 2- (tert-butylamino) -3- (3-triethoxysilylpropyl) 4-pentanone obtained as above, and heated under reflux for 18 hours with stirring to prevent overheating. The modified silica was then filtered off and unreacted silane was removed by washing the silica with toluene in a Soxhlet apparatus. The washed and dried sorbent contained 12.99% carbon, 2.57% hydrogen, 0.9% nitrogen, and its specific surface area was 349 m ² / g.

C. Preparation of the column

The capillary column (30 m × 0.32 mm) was pre-washed with methylene chloride and dried under argon for 1 hour. Polymethylhydrogen siloxane (GE Silicones SL6020-D1) was dissolved in a mixture of methylene chloride and pentane (4: 1) - the concentration of the solution was 12.25 mg / cm ³ . After filling the capillary, one end was closed, the column was placed in a bath at 40 ° C, the other end was connected to a vacuum and the solvent was removed. On the thus prepared column, the packing obtained as in Example 1B was applied. The packing was placed on the column as follows: A packing was placed in the tank through which the inert gas flows freely. It was then suspended in this gas by subjecting the vessel to vibration. The slurry was drawn into the column by placing one end of the column in the vessel and the other end by connecting a vacuum pump. In order to keep the column suspended and ensure that the packing was evenly applied to the walls of the column, the entire system, ie the vessel and the column, was vibrated until the process was complete.

Upon completion of this process, the polysiloxane was polymerized by bubbling azo-tert-butane vapor through the column for 1 hour. Then both ends of the capillary were closed and the column was heated from 30 ° C to 220 ° C at a rate of 1 ° C min ^-1 and held at this temperature for 1 hour. After cooling, the column was washed with methylene chloride, dried under argon and conditioned by heating from 20 ° C to 220 ° C in 1 ° C min ^-1 increments.

D. Chromatographic separation

The column, prepared as in Example IC, was used to separate a mixture of cyclic hydrocarbons. The analysis was performed using a column temperature of 120 ° C and a carrier gas (helium) flow rate of 1.3 cm ³ / min. The obtained separation is shown in Fig. 2 of the figure, where 1 is methylcyclopentane, 2 - cyclohexane, 3 - cyclohexene, 4 - 1,3-cyclohexadiene, 5 - 1,4-cyclohexadiene, 6 - 4-methyl-1-cyclohexene, 7 - 1-methyl-1-cyclohexene and 8 - 1,3,5-cycloheptatriene.

P r z x l a d II

A. Preparation of silane

Proceeding as in Example 1A and using (R) - (+) - α-methylbenzylamine instead of phe (N) - methylbenzylamine gave (+) - 2- (1-phenylethylamino) -3- (3-triethoxysilylpropyl) pentanone-4.

Elemental analysis: determined [%]: Si - 6.97, C - 64.80, H - 9.01, N - 3.50 calculated [%]: Si - 6.88, C - 64.86, H - 9.09, N - 3.44;

MS: m / z - 392 [M-15] ⁺ , m / z - 364 [M - 43] ⁺ ;

In the IR spectrum, characteristic bands for the carbonyl group: 1735 cm ^-1 (ν CO), and for the imino group 1610 cm ^-1 (ν C = N).

B. Preparation of the filling

Proceeding as in Example 1B, the packing was prepared with the silane obtained in Example 2A

The washed and dried filling contained 18.27% carbon, 2.58% hydrogen, 1.24 nitrogen, and its specific surface area was 327 m ² / g.

C. Preparation of the column

By proceeding as in Example IC, a column was obtained in which the packing obtained according to Example 1B was placed on the capillary walls.

PL 206 989 B1

D. Chromatographic separation

The optically active compounds were separated on the column prepared as in Example IIC. The analysis was performed using a column temperature of 70 ° C and a carrier gas (helium) flow rate of 1.0 cm ³ / min. The resulting separation is shown in Fig. 1 of the figure, where 1 is (-) - 2-bromobutane, 2 - (+) - 2-bromobutane, 3 - (-) - 2-bromopentane, 4 - (+) - 2-bromopentane .

Claims (1)

Patent claim A packing for gas chromatography in which an organosilicon compound is chemically bonded to a mineral carrier, characterized in that the organosilicon compound is a ketimine derivative of the general formula in which R ¹ and R ² are equal or different and represent an alkyl group containing from 1 to 6 atoms carbon in the molecule, n is an integer from 1 to 3, m is an integer from 1 to 10, and R ³ is an alkyl or aryl group optionally containing at least one optically active carbon atom.