SU1453320A1 - Method of chromatographic analysis of aromatic amines - Google Patents

Abstract

The invention relates to analytical chemistry and can be used for the analysis of microimpurities in aromatic amines by liquid chromatography with gradient blending. The purpose of the invention is to reduce the duration and complexity of the analysis. The sample is fed to the chromatographic COLUMN, filled with silica gel, modified with octadecylsilane. The separation is carried out with a gradient mobile phase. As an gradient phase, an eluent is used, obtained by mixing two solutions, the first of which contains,%: 1 / 15-1 / 1 OHM phosphate buffer solution 90-98; methanol 2-10, and the second solution contains the same ingredients in inverse proportions. The mixture of two solutions is carried out in a mixture of Tejje with a uniform change in the content of the second solution in the mixture according to the following regime: 0-15 min O - (5-10)% 16-30 min (5-10) - (40-45 )%, 31-45 min (40-45) - (90-95)%; 46-50 minutes (90-95) - (5-10)%. 1 hp f-ly, 9 ylo c (L 1 ate 00 bo to

Description

The invention relates to analytical chemistry and can be used to analyze trace impurities in aromatic amines using liquid chromatography with gradient elution.

The purpose of the invention is to reduce the duration and complexity of the analysis.

Figure 1 shows the chromatogram of a reference mixture of aromatic amines, nitro and halogen compounds in figure 2; comparative chromatograms of p-aminophenol and its oxidation products at different intervals of its solution of solutions in methanol at 293 Kj in figure 3 - combined chromatograms of four industrial samples of DADPE (4,4-diaminodiphenyl ether); Fig. 4 shows a chromatogram of a reference mixture of aromatic compounds with a proportionally varying gradient elution mode; 5 - 6 - chromatograms of the reference mixture obtained in two isocratic elution modes, 7 - combined chromatograms of the reference mixture of aromatic compounds, obtained by changing the pH of the buffer solution in Fig. 8 - chromatogram of the reference mixture of aromatic compounds

compounds obtained by changing the boundary values of the content of eluent ingredients; Fig. 9 is a chromatogram of the reference mixture obtained by changing the content of eluent (boundary values).

The method is carried out as follows.

The sample is fed to a chromatographic column filled with silica gel, modified with octadecylsilane. The separation is carried out with a gradient mobile phase. An eluent is used as a gradient phase, obtained by mixing two solutions, the first of which contains the following ingredients, vol.%:

1 / 15-1 / 10 M phosphate

buffer solution 90-98

Methanol2-10

and the second solution contains the same ingredients in inverse quantitative terms.

The mixture of two solutions is carried out in a mixer with a uniform change in the content of the second solution in the mixture according to the following mode:

0-15 min from 0 to 5-10%;

A-30 min from 5-10 to 40-45%;

5 about 5

0

0

31-45 min from 40-45 to 90-955,: 46-50 min from 90-95 to 5-10%. Example 1. A mixture of 9 reference compounds and DADPE (10 µg each in 20 µl of methanol) is injected into the chromatographic column: p-nitrochlorobenzene, p-nitrophenol, p-aminophenol, p-chloroanalin, 4-5-dinitrochlorobenzene, 4,5-diaminophenol, 4,4-dinitrodiphenyl ether, 5-triaminodiphenyl ether, 3,4,4,5-tetraaminodiphenyl ether.

Bulk eluent flow rate 12 CMV4.

As eluent, a mixture of a solution containing the following constituents is used. %: 1/15 M phosphate buffer solution with pH 7.4 95 Methanol5

with a solution containing the same ingredients in inverse terms,% by volume:

1/15 M phosphate buffer solution with pH 7.45

Methanol. 95 Phosphate buffered saline is prepared in a standard manner.

The solutions are mixed in a specially designed mixer with a change in the amount of the second solution in the following mode, vol.%:

0-15 min - from 0 to 5 j 16-30 min - from 5 to 40; 31-45 min - from 40 to 95; 46-50 min 4 from 95-5. P and M e p. 2. Similar to Example 1, comparison of the chromatograms of p-aminophenol (as an example), obtained at different times for holding solutions in methanol at 293 K., was carried out. Visible is the increased instability of aromatic compounds in solutions due to its oxidation. The chromatogram is presented in figure 2.

Prima rz. Under the conditions of Example 1, four industrial samples of DADPE were analyzed. Sample concentration 2 mg / ml. Chromatograms are not shown in FIG.

Example 4: The separation of the reference mixture was carried out under the conditions of Example 1, but with a proportionally increasing gradient of methanol concentration (from 0 to 100% by volume). Figure 4 presents the chromatogram and simultaneously the change in the concentration of methanol in the eluent.

31

p 5. The division of the reference

Prime

the mixtures were carried out under the conditions of example 1, but with a constant concentration of methanol in the eluent (isocratic mode of elution). The chromatogram in figure 5 is made with a methanol content in the eluent of 25% by volume. Figure 6 presents the chromatogram when the content of methanol in the eluent 75 vol.%.

PRI me R 6. The separation of the mixture is carried out under conditions of example 1, but with a change in the pH of the buffer solution. Figure 7 shows the chromatograms obtained with 4 phosphate 1/15 M standard buffer solution.

Example 7. The separation of the reference mixture was carried out under the conditions of Example 1, but with a variation of the elution mode (boundary, values of the content of eluent ingredients). 8 shows a chromatogram. For comparison, a dotted line is applied. Chromatogram obtained according to Example 1. Elution is carried out by mixing a first solution containing,%:

1-15 M phosphate

. buffer with pH 6.8, Methanol with a second solution,

1/15 phosphate

pH 6.8 buffer

Methanol

the next mode.

by

98 2

containing,%:

2

98 providing

mu content in

thief,%:

0-15 minutes 16-30 minutes 31-45 minutes 46-50 minutes Prime

The eluent of the second plant. The creation of the required pH of 6.8-7.5 is carried out with phosphate buffer for the following reasons. Phosphate ions prevent corrosion of metal surfaces (a surface layer forms, which passivates the surface). The use of other types of standard buffers is confronted with the use of strong acids. For example, for

from O to 10;

from 10 to 35}

from 35 to 90;

from 90 to 10.

p 8. The separation of the reference mixture is carried out under the conditions of example 1, but with a variation of the elution mode (Fig. 9). For comparison, a dotted line is applied. supplying a buffer based on a tetrabram template of the reference mixture obtained with sodium (pH 7.4) is required 0-15 minutes 16-30 minutes 31-45 minutes 46-50 minutes

from from

O to 5} 5 to 45;

five

-from 45 to 90i

-from 90 to 5.

The resulting chromatogram is almost identical to that shown in Example 1.

The concentration of the phosphate buffer solution is 1 / 15-1 / 10 M. A decrease in the concentration below the standard value (1/15 M) leads to a sharp decrease in the buffer capacity of the solution. Increasing the concentration (above 0.1 M) increases the viscosity of the eluent, worsens the solubility of the reference compounds, makes it difficult to mix the two components of the eluent solutions and remove the dissolved gas from the solution, which distorts the results of the analysis. to a noticeable distortion of the results of the analysis.

The pH of the buffer solution is 6.8-7.5. Lowering the pH (below 6.8) results in poor reproducibility of the chromatographic separation of the reference mixture. An increase in pH (cvEr 7.5) reduces the service life of chromatographic columns packed with silicate sorbents, due to the increased dissolution of the sorbent matrix and its graft phase in alkaline media.

The creation of the required pH of 6.8-7.5 is carried out with phosphate buffer for the following reasons. Phosphate ions prevent corrosion of metal surfaces (a surface layer forms, which passivates the surface). The use of other types of standard buffers is confronted with the use of strong acids. For example, for

five

0

five

 buffer based on sodium tetrabrate (pH 7.4) is required

according to example 1. Elution is carried out by mixing the first solution containing, 7

/about "

1/10 M phosphate buffer with pH 7.5 90, Methanol,

with a second solution containing,%: 1/10 M phosphate buffer10,

Methanol90

in the following mode, providing the content in the eluent of the second solution, about. %:

0

five

on acid. The latter leads to a rapid failure of the chromatograph and column pumps.

The eluent contains a first solution consisting of a phosphate buffer with the addition of 2-10% by volume of methanol and a second solution (B), mainly consisting of methanol with the addition of 2-10% by volume of a buffer solution. Small additions in the first case of methanol, and in the second case of the buffer solution, are due to the fact that this improves and accelerates the mixing

both solutions without the need to compensate for the temperature effect of the mixing reaction.

In addition, as the experiment showed, the proposed method prevents the use of gas dissolved in the eluent in the chromatographic column, hydraulic circuits and detector, which is promoted by a large pressure drop at the inlet to the chromatographic column (100-150 kgf / cm) and output - About kgf / cm and, thus, no preliminary procedure for degassing the eluent solutions is required.

The elution mode is justified by experimental selection of conditions. Departure from it is associated with a sharp deterioration in the resolution of the chromatographic process and a decrease in reproducibility.

The proposed method provides a clear separation into components of a reference mixture of aromatic amines, nitrates and halogenated compounds and a real industrial sample of DADPE on the same sorbent using a single gradient eluent.

75

g5

Claims (2)

1. A method of chromatographic analysis of aromatic amines, nitro and halogen-based, by reverse phase liquid chromatography on octadecylsilane-modified silica gel columns and gradient mobile phase, characterized in that, in order to reduce the duration and complexity of the analysis, eluent 4 is used as a gradient phase obtained by mixing two solutions, the first of which contains ingredients,%, 1 / 15-1 / 10 M phosphate buffer solution with pH 6.8-7.590-98 Methanol2-10 and the second solution contains the same ingredients in an inverse proportion. 2. Method POP.1, characterized by the fact that the mixing of the eluent ingredients is carried out with a change in the content of the second solution in the mixture over time according to the mode a) 0-15 minutes from 0 to 5-10%; b) 16-30 minutes from 5 to 40-45% i c) 31-45 min from 40-45 to 90-95% d) 46-50 min from 90-95 to 5-10%. 100% -80 -60 -W th ten 35 1 five TO % CH, OH f49№ gs m% FIG. four .. K% en %. CHZON 75% CfhO 15 Z5 SB V w 0 t w5 tw .. mei. is SB 40 w .0 35 45 15 2S % .Cft, Y0 % SMZON  1 (I% 35 ts