A method of producing a sorbent for gas-liquid chromatographic analysis

 

(57) Abstract:

The invention relates to a method of analysis of organic compounds. The method of preparation of the sorbent for gas-liquid chromatographic analysis of thermolabile organic compounds using apiezon as the stationary liquid phase includes applying a liquid phase onto a solid carrier and thermal conditioning of the resulting sorbent. The activity of the stationary liquid phase, leading to thermal decomposition of organic compounds in Packed column in the analysis, inhibit ammonia. For this dry sorbent after application of the liquid phase is maintained at 420 490C in an atmosphere containing ammonia partial pressure of 0.005 to 0.6 MPa, for 2 to 8 hours causes irreversible inhibition of the catalytic activity of the stationary phase. 4 C. p. F.-ly, 2 Il.

The invention relates to a method of analysis of organic compounds and can be used for gas-liquid chromatographic (GLC) analysis of thermolabile organic compounds, for example, in the preparation of the sorbent with opitonui as stationary phase.

The known method GC analysis of thermolabile compounds, comprising preparing Sorb is eat (PEG-40) or carbowax-20 m, with the objective of reducing the chemical activity of the surface of the carrier [1]

The disadvantage of this method will affect only carrier without a decrease in activity in the reactions of thermal decomposition of high molecular weight (M. C. 240) organic compounds inherent to some stationary liquid phases, in particular hydrocarbons complex composition common name apiezon with different letter indexes. Thanks to the good selectivity in a wide range of functional groups of organic compounds and simultaneously sufficient temperature stability, sorbents with opitonui as the stationary liquid phase is intensively used in GC analysis of various chemical products. However, the analysis of macromolecular compounds requiring high temperatures, in some cases in column observed thermal decomposition of the analyzed compounds caused by the presence apiezon stubborn impurities. The products of thermal decomposition in the column do not form at the entrance to the detector narrow peaks and appear as a broad shoulder of irregular shape, adjacent to the beginning of the true peak decaying product. This leads to less accurate definition of the product and at the same time masks the expression of the chromatogram peaks the effect of the processes of thermal decomposition in a known method of preparation of the sorbent for GC analysis of products obtained in the production isophytol (3,7,11,15-tetramethylhexadecane-1-EN-3-ol intermediate for the synthesis of fat-soluble vitamins E and K1) catalytic hydrogenation dihydrosafrole (acetylene alcohol203,7,11,15-tetramethylhexadecane-1-in-3-ol) apiezon put on a solid support (usually chromatin or inerton) in a mixture with polyethylene glycol (PEG-40) or carbowax-20M than simultaneously achieve reduction of chemical activity and solid media [2]

The disadvantage of the prototype using sorbent with higher content of stationary phase that significantly increases the duration of the analysis, or requires holding it at an elevated temperature. Long-term analysis does not meet the conditions of the operational control of the production process, and the analysis at elevated temperature accelerates the outflow from the column having the higher vapor pressure of the glycol. Because of this, in the stationary liquid phase is continuously changing the contents of apiezon and polyethylene glycol and accordingly change the basic parameters of the column, which leads to deterioration of the accuracy of the analysis.

The invention consists in that in the method of preparation of the sorbent with ispolni, including the application of the liquid phase on the solid medium and the conditioning of the resulting sorbent known methods, before the conditioning process sorbent ammonia at a partial pressure of ammonia from 0.005 to 0.6 MPa and the subsequent curing of the sorbent in the environment within 2-8 h at 420-490 K.

The purpose of the invention is that when using ammonia for handling sorbent irreversibly inhibited the catalytic activity of the stationary phase (apiezon all types), leading to thermal decomposition of the analyzed products. In result, it becomes possible to improve the accuracy of GC analysis and to eliminate masking the decay products of the peaks of the components of the low concentrations included in the analyzed mixture.

In Fig. 1 shows the chromatogram technical isophytol before processing column ammonia where: 1 ketone182 decay products, 3 isophytol, 4 digitization; Fig. 2 is the same, after processing column ammonia, where: 1 ketone18, 2 acetylene alcohol WITH20, 3 isophytol, 4 digitization.

On solid media from a solution of the calculated concentration put apiezon (usually L, M or N) one of the known methods and dried sorbent to remove solvent. Prigotovlenn is squeezed from her air with gaseous ammonia, in the absence of a source of dry ammonia inert gas (helium, nitrogen), previously passed through a bubbler filled with a concentrated aqueous solution of ammonia, for 10-20 minutes Then a tank filled with sorbent is heated to 420-490 and To stand in an atmosphere with a partial pressure of ammonia from 0.005 to 0.6 MPa within 2-8 hours

After treatment with ammonia sorbent condition known methods to fill in a Packed column or directly in the column.

The implementation described sequence of operations allows to suppress the decay of thermolabile organic compounds in Packed column, that like the GC analysis of the technical isophytol illustrated in Fig. 1 and 2. From the comparison of these chromatograms, it follows that the suppression of the decay process in addition to improving the accuracy of the content isophytol allows for the same chromatogram to determine the residual content of the original acetylene alcohol15, chromatographic peak which to handle ammonia sorbent to remove the products of thermal decomposition and which was determined by argentometric titration with a large error because of actionstitle on the basis of experimental data and due to the following reasons.

It is established that at a sufficient temperature and time of processing the complete suppression of the chemical activity of a stationary liquid phase from the partial pressure of ammonia is substantially not affected, so the range of the specified partial pressure is determined mainly by sources of ammonia, where the lower limit applies to the case of using an aqueous solution of ammonia, and the top to receive ammonia from standard gas cylinders in terms of its use as a carrier gas for long columns with fine-grained sorbent.

Found that the impact on the raw liquid phase temperatures close to the upper temperature limits recommended for apiezon different brands, leads to an irreversible increase in the intensity decay of the analyzed compounds, at the same time significantly and irreversibly deteriorating the efficiency of the separation provided by the sorbent.

For these reasons, it is necessary to avoid work at temperatures less than 50 To approaching the upper temperature limit of apiezon that limits the upper temperature limit in the processing of ammonia 490 To that for the same reasons is limiting the temperature of condizioniatore thermal decomposition of the analyzed products is growing in the row N < M < L < K and by increasing the concentration of immobile liquid phase and the rate of suppression of their chemical activity of ammonia at reduced temperature drops quickly. In addition, GC analysis of the products with high molecular weight are at high enough temperatures, therefore, the lower limit of the temperature during the processing of ammonia sorbent 420 To selected in order to provide an acceptable processing time of the sorbent and at the same time to be not lower than the temperature of the possible use in the analysis.

Experiments with sorbents containing apiezon K, L, M and N with weight concentration of 3-8% show that with appropriate choice of treatment temperature and the chemical activity of most of the sorbents can be quite deeply depressed for 2-8 hours

Qualitative analysis of the chromatograms of the various compounds obtained with the use of sorbents with different brands of apiezon, does not reveal significant differences in the manner and time of output of analyzed compounds from the chromatographic column, which is a consequence of the affinity constants Mac Reynolds, characterizing the stationary liquid phase on selectivity for apiezon different brands.

In the series studied apiezon the influence of high temperatures has as installed, apiezon N. it is also Shown that after treatment with ammonia chemical activity of apiezon N is suppressed most fully and irreversibly, whereas for apiezon other brands arises the necessity of repeated treatments. For these reasons, when choosing a brand of apiezon as a stationary liquid phase for GC analysis of thermolabile organic compounds preferably using apiezon n

A practical example of the method of preparation of the sorbent for GC analysis of thermolabile organic compounds are given in the methodology GLC analysis of the mass fraction of acetylene alcohol20, isophytol and dihydrosafrole (product exhaustive hydrogenation of the alcohol WITH20in technical isofemale produced by Bolohivski chemical combine synthetic intermediates and vitamins.

According to this technique on solid media (inerton, chromaton N or zithrom, graining 0,100-0.125 mm or 0.125-0,160 mm) applied filtration method [1] apiezon N at 2% (zithrom), 3% (Enercon) or 3-5% (chromaton N) of the weight of the solid carrier. The dried sorbent fill the Packed chromatographic column, which will later have to separate the mixture of analiziruemykh (supply of 1-5 ml/min) or inert carrier gas (supply of 10-20 ml/min); sent through a bubbler filled with an aqueous solution of ammonia, is heated column thermostat chromatograph to 450-470 To and kept at this temperature for 3-4 hours, not stopping to blow through a column containing ammonia or inert gas.

After processing of the sorbent ammonia, condition the column at a flow rate of carrier gas 50-60 cm3/min to 1 hour at a temperature of 370 K and 2 h at 450 K, the transition between these temperatures with a linear speed of 1 deg. /min. Stripping column after treatment with ammonia and air conditioning is carried out at 450 To the disappearance of the drift of the zero line (2-3 h).

To assess the intensity decay in the prepared column, record the chromatogram isophytol (preferably imported) under the following conditions: the temperature of the evaporator, thermostat and flame ionization detector chromatograph 450 K, the speed of the carrier gas (helium, nitrogen) 50 cm3/min, vcol samples isophytol (without solvent) of 0.12 to 0.14 mm. The sensitivity of the chromatograph during the registration peaks of impurity products and degradation products installed in 30-50 times higher sensitivity, in which register the peak of the main product. The intensity decay estimate by type of participation is the willingness of the speakers to work) to be valid, when the chromatogram clearly prescribed peak acetylene alcohol20when its content in isofemale of 0.1-0.2% otherwise handling sorbent ammonia and subsequent conditioning of the column again.

Processing sorbents with opitonui ammonia eliminates the disintegration of other thermolabile organic compounds when they are present in the sample as the main or in appreciable concentrations. This applies, in particular, to the original acetylene alcohol WITH20the product its full hydrogenation dihydrosafrole, the precursors for the synthesis of alcohol20limit and unsaturated ketones18and also intermediate of the synthesis of vitamin And ciolino20actually vitamin a and a variety of products of hydrogenation, which significantly expands the possibilities of the practical use of this method of preparation of sorbents for GC analysis.

Besides the positive effects, the proposed method in comparison with the method prototype allows the use of sorbents with low content of stationary liquid phase, which increases the efficiency of separation of the products and creates the possibility of acceleration analysis with simultaneous reduced the but increases its service life.

1. A METHOD of producing a SORBENT FOR gas-LIQUID CHROMATOGRAPHIC analysis of thermolabile organic compounds using apiezon as the stationary liquid phase, including the application of the liquid phase on the solid carrier and thermal conditioning of the sorbent, wherein after application of the liquid phase sorbent is dried and incubated in an atmosphere containing ammonia, with a partial pressure of 0.005 to 0.6 MPa at 420 490 To within 2 to 8 hours

2. The method according to p. 1, characterized in that as the atmosphere containing ammonia, inert gas passed through an aqueous solution of ammonia.

3. The method according to PP.1 and 2, characterized in that the exposure of the sorbent in immixture atmosphere is carried out in a Packed chromatographic column.

4. The method according to PP.1 to 3, characterized in that as the stationary phase used apiezon n

5. The method according to PP.1 to 4, characterized in that the conditioning is carried out at a temperature of not less than 50obelow the upper temperature limit for the used apiezon.

 

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