The method of determination of isomers of 3-phenoxy-lebenshilfe ester 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1 - carboxylic acid

 

(57) Abstract:

The method of determination of isomers of 3-phenoxy--Lebenshilfe ester 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylic acid by high performance liquid chromatography. As stationary phase used sorbent is silica-based. As eluent a mixture of hexane with tetrahydrofuran or ethyl acetate at a volume ratio of 100 : 0.1 to 0.6. The technical result of the claimed invention is expressed in the creation of a more effective way of determining the isomers 3-phenoxy--Lebenshilfe ester 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylic acid.

The invention relates to analytical chemistry, namely, to methods for determination of isomers of 3-phenoxy--cyclopentolate ester 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cypermethrin) by high performance liquid chromatography (HPLC). The invention can be used in analytical laboratories.

Cypermethrin refers to PYRETHROID insecticides and is a mixture of CIS - and TRANS-isomers. Molecule cypermethrin has three centers of asymmetry, each of which are formed (R)- and (S)-isomers, i.e. forms/BR> 3) /IR/R + /IS/S;

4) /IR/S + /IS/R.

(Pyrethroids. Chemical-technological aspects./Ed. by C. K. Romanenkova. - M.: Chemistry, 1992, pp. 264-266).

Since the biological activity of individual isomers of cypermethrin differ from each other, it is important to know the content of cypermethrin.

In particular, for practical purposes in the production of cypermethrin is important to know the content of 4 diastereomers without separation of individual enantiomers. For example, certain drugs on the basis of cypermethrin is a mixture of the second and fourth enantiomeric pairs with the highest biological activity, while the first and third enantiomeric pairs contained in the preparations as impurities.

Known methods of determination of isomeric compounds by HPLC. So, there is a method of quantitative determination of ortho-, para-, metasomal nitrobenzoic acid. As stationary phase using sorbent separon C18or silsor C18as eluent using an aqueous solution of sodium hydrogen phosphate when its concentration in eluent 0.3 to 1.5 wt.% (ed. St. USSR N 1656477).

There is also known a method of determining geometric (SYN-anti) isomers of 2-(2-amino-out sorbent silsor C8or C18as the mobile phase using water containing organic modifier acetonitrile or ethanol in the amount of 11-33%. (AB. St. USSR N 1589205).

It should be noted that the choice of adsorbent, eluting solvent mixtures and ratios in liquid chromatography and, in particular HPLC, is not obvious. Chromatographic separation can occur as a normal phase variant and column with reversed phase. General trends in the development of methods for detecting chemical compounds using HPLC described in source (E. L. Stiskin, L. N. Itzykson, E. C. Braude. Practical high-performance liquid chromatography. -M.: Chemistry, 1986).

As the closest analogue is selected Pat. The USSR, N 1349697, from which it follows that it is known the use of HPLC (according to U.S. Pat. USSR N 1349697 - liquid chromatography high resolution) to determine the two isomers of cypermethrin, belonging to the second enantiomeric pair /IR/S + /IS/R. the Definition of exercise on the stationary phase using an organic solvent, however, the conditions of the analysis and the possibility of defining other isomers of cypermethrin is not disclosed.

The objective of the proposed isobilateral-1-carboxylic acid, in particular the 4 diastereomers in cypermethrine by HPLC.

The proposed method for the determination of isomers of 3-phenoxy--Lebenshilfe ester 3-(2,2-dichloroethyl)-2,2-dimethylcyclopropane-1-carboxylic acid in cypermethrine is to chromatographic separation by HPLC of the sample on the stationary phase, representing the sorbent is silica-based, organic eluent from a mixture of hexane with tetrahydrofuran or ethyl acetate at a volume ratio of 100 : 0.1 to 0.6. Registration of the divided areas (peaks) is carried out using spectrophotometric detector at a wavelength of 254 nm. Mass fraction is calculated by the method of external standard peak areas. The sequence of output of 4 diastereomers cypermethrin:

1) /IR/R + /IS/S;

2) /IR/S + /IS/R;

3) /IR/R + /IS/S;

4) /IR/S + /IS/R.

The chromatogram 16 - 22 minutes. The total error in determining the amount of the isomers is not more than 1.5%.

Example 1.

Pre-prepare two calibration solution cypermethrin - sample for calibration with a known percentage of each of the four diastereomers. For this purpose a portion of 25-40 mg of sample siperm is as eluent a mixture solvent of hexane and tetrahydrofuran in a volume ratio of 100 : 0,1. Similarly prepare two solutions of the samples analyzed cypermethrin (solutions N 3 and N 4). Using the dispenser injected aliquot (20 ál) of the resulting solutions into the flow of eluent in the following order: N 1, N 3, N 2, N 4, repeating enter two more times. The separation is carried out on a column (250 x 4.6 mm) with a fixed phase, representing a silica gel brand Ultrastar CN at a flow rate of eluent 1.1 ml/min Detection components carry out spectrophotometric detector at a wavelength of 254 nm. The mass percentage of each isomer is calculated by the method of external standard peak areas.

The sequence of output of 4 diastereomers cypermethrin:

1) /IR/R + /IS/S;

2) /IR/S + /IS/R;

3) /IR/R + /IS/S;

4) /IR/S + /IS/R.

On the obtained chromatograms calculate calibration factors (Kifor each isomer by the formula

< / BR>
where marticle- the weight of cypermethrin sample for calibration;

Sithe peak area of i-isomer of cypermethrin in the chromatogram of the calibration solution;

Pi- mass fraction of i-isomer in cypermethrine - sample for calibration, %.

Then calculate the mass percentage Xithe % of each of EPA cypermethrin;

mCR- the weight of the portion of the analyzed sample;

Sxithe peak area of i-isomer in the chromatogram of the analyzed sample.

After calculating chromatograms receive the following contents of 4 diastereoisomers in the analyzed sample cypermethrin:

1) /IR/R + /IS/S - 0,6%;

2) /IR/S + /IS/R - 39,7%;

3) /IR/R + /IS/S - 0,6%;

4) /IR/S + /IS/R - 57.6 Per Cent.

Example 2.

The analysis is performed analogously to example 1 except for the volume ratio of the components of the eluent, which is hexane : tetrahydrofuran 100 : 0,2.

After calculating chromatograms receive the following contents of 4 diastereoisomers in the analyzed sample cypermethrin:

1) /IR/R + /IS/S - 0,6%;

2) /IR/S + /IS/R - 39,0%;

3) /IR/R + /IS/S - 0,7%;

4) /IR/S + /IS/R - 57,0%.

Example 3.

The analysis is performed analogously to example 1 except for the volume ratio of the eluent components and brands of used sorbent. The ratio of the components eluent hexane : tetrahydrofuran of 100 : 0.3 to. As stationary phase using silica gel brand Ultrasphere Si.

After calculating chromatograms receive the following contents 4 diastereomer the+ /IS/S - 0,6%;

4) /IR/S + /IS/R - 58,0%.

Example 4.

The analysis is performed analogously to example 1 with the exception of co-solvent in eluent, volume ratio of the components of the eluent, a flow rate of eluent and brands of used sorbent.

As a co-solvent in eluent using ethyl acetate at a volume ratio of the components of the eluent hexane : ethyl acetate 100 : 0,4. As stationary phase using silica gel brand Ultrasphere Si. The rate of flow of eluent 2 ml/min

After calculating chromatograms receive the following contents of 4 diastereoisomers in the analyzed sample cypermethrin:

1) /IR/R + /IS/S - 0,7%;

2) /IR/S + /IS/R - 39,2%;

3) /IR/R + /IS/S - 0,5%;

4) /IR/S + /IS/R - 58,6%.

Example 5.

The analysis carried out analogously to example 4 except for the volume ratio of the components of the eluent, which is hexane : ethyl acetate 100 : 0,6.

After calculating chromatograms receive the following contents of 4 diastereoisomers in the analyzed sample cypermethrin:

1) /IR/R + /IS/S - 0,7%;

2) /IR/S + /IS/R - 40,1%;

3) /IR/R + /IS/S - 0,5%;

4) /IR/S + /IS/R - 56,6%.

The method of determination of isomers of 3-f the objective liquid chromatography on a stationary phase using an organic solvent, characterized in that as the stationary phase used sorbent is silica-based and as eluent a mixture of hexane with tetrahydrofuran or ethyl acetate at a volume ratio of 100 : (0.1 to 0.6).

 

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