Method of detecting water-soluble vitamins in premixes

FIELD: chemistry.

SUBSTANCE: invention relates to analytical chemistry. The method is realised as follows: a sample of ground up premix is filled with a hydrochloric acid solution and put into an opaque case which is put into an ultrasonic bath. Extraction is carried out for 15-20 minutes at 38-42°C and centrifuging is then carried out for 10 minutes at 8000 rpm. The mixture is then brought up to the mark in a measurement flask. The obtained solution undergoes chromatographic separation on a column with Purospher sorbent. Chromatography conditions: eluent A - 0.005 M lithium perchlorate solution, pH=2.5; eluent B- acetonitrile; elution gradient mode - from 0 to 26% eluent B for 14 minutes.

EFFECT: high efficiency and accuracy and possibility of detecting a wider range of vitamins independent of the premix base.

2 dwg, 5 tbl, 1 ex

 

The invention relates to analytical chemistry, namely the sections of extraction and chromatography. It can be used for chromatographic analysis in medicine and agriculture.

A known method for the determination of water-soluble vitamins (see GOST R 50929-96 "Methods for the determination of vitamins"). The essence of the method consists in the extraction of vitamins (B1, B2 and B5) of the sample solution of hydrochloric acid: a suspension of 1 g + 10 ml of hydrochloric acid concentration of 0.01 mol/l, the extraction is performed on the magnetic stirrer with heating for 10 minutes, centrifuged at 5000-6000 rpm for 3 minutes, bring in a volumetric flask of 25 ml to label with subsequent chromatographic analysis. The chromatography was carried out carried out in the following conditions: eluent (120 ml acetonitrile + 880 ml of water + 2.5 ml of triethylamine, 0.5 g octisalate sodium + orthophosphoric acid to pH of 7.6 on the pH meter), isocratic mode of elution, the rate of elution of 1.2 ml/min, the working wavelength spectrophotometric detector at 254 nm.

However, the known method to determine the mixture of only three vitamins - B1, B2 and B5, and the use of expensive ion-pair reagent articulate sodium reduces the resource column does not allow to work in gradient mode, in addition, this method is not applicable for premix mineral-based.

From the description of the data in the literature closest to the invention is a method proposed by Lanovoy L.A., Fedorova GA and GI Barama innovation center "Determination of water - and fat-soluble vitamins in multivitamin preparations by high performance liquid chromatography" AH, 2002, vol. 57, No. 1, 49-54, the extraction was carried out with a solution of lithium perchlorate in water (0.4 mol/l, pH of 2.4. Hitch 0.1-0.2 g + 20 ml of a mixture of perchlorate with 0.1% solution of butylacetamide (19:1 by volume), was stirred in the dark for 10 minutes at pH 5.5. If the pH value not established itself, brought hydroxide solution lithium, then brought the pH to 2.4 and were extracted for another 10 minutes. Added volumes were taken into account when calculating the concentrations. The chromatography was carried out was performed under the following conditions: eluent A - 0.4 M lithium perchlorate (LiClO4pH 2,4); eluent B - acetonitrile; gradient - 8 min 2% B, 17 minutes linear gradient from 5% to 18% B; flow rate 0.1 ml/min; temperature 35°C; the volume of the sample 4-10 ál. Registration started at 6 wavelengths(210, 220, 250, 260, 280, 300 nm). The duration of the pickup 25 minutes.

However, the proposed method is long and complicated technology, not applicable for premix mineral-based.

With the development of large-scale production and active introduction of multivitamin preparations both in agriculture and in medicine and food industry tightened control of their quality not only from the manufacturer, but also by p is the consumer. Consequently, it is important the analysis of a wider range of vitamins.

The objective of the invention is to improve the efficiency and accuracy of the method, identifying a broader range of vitamins, regardless of the basis of the premix.

The problem is solved as follows: the sample is pre-crushed premix is poured a solution of 0.01 N. hydrochloric acid, placed in a light-tight casing, which is mounted on the ultrasonic bath. The ratio of the sample and extractant picked so that the concentration of vitamins fall into the range of linearity of the developed chromatographic methods. Extraction spend 15-20 minutes at a temperature of 38-42°C. and Then centrifuged for 10 minutes at 8000 rpm, bring up to the mark in a volumetric flask. The resulting solution was used for chromatographic analysis. Chromatographic separation carried out on a column (250×4 mm with a sorbent Purospher RP-18e (5 µm). Chromatograph conditions were as follows: eluent A - 0.005 M solution of lithium perchlorate pH of 2.5; eluent B - acetonitrile; gradient elution mode from 0 to 26% of eluent B over 14 minutes. The injected volume of 40 ál. The wavelength of detection: UV detector from 0 to 8 minutes 250 nm, 8 to 10 minutes 200 nm, 10 to 12 minutes 230 nm, from 12 to 18 minutes 200 nm; fluorescence detector when the absorption at 270 nm from 0 to 12 minutes at 400 nm (luminescence), from 12 to 18 minutes to 495 nm (luminescence is).

Distinctive features of the proposed method are extracted using ultrasound for 15 to 20 minutes at a temperature of 38-42°C, centrifuged for 10 minutes at 8000 rpm, as the eluent used solution of lithium perchlorate concentration of 0.005 M, gradient elution from 0% to 26% acetonitrile in 14 minutes.

Extraction with ultrasound for 15 to 20 minutes at a temperature of 38-42°C allows to achieve a given completeness of extraction of vitamins premixes on any basis.

Centrifugation at 8000 rpm for 10 minutes allows you to achieve a more complete separation of the phases.

The proposed variant of the gradient allows to reduce the time of pickup from 25 to 18 minutes, while maintaining the quality of separation. It is established that lithium perchlorate concentration of 0.005 M, used only as a mobile phase, has a sufficient ion-pair effect on vitamins (improving the shape of the chromatographic peak), allows to achieve a given degree of separation (the separation criterion in all cases is greater than 1) and slightly pollutes the column.

The proposed method for the determination of water-soluble vitamins allows you to expand the Arsenal of up to 9 vitamins regardless of the basis of the premix is reliable and simpler technology.

EXAMPLE.

The determination of vitamins is as follows: the sample previously is smallchange premix is poured a solution of 0.01 N. hydrochloric acid (ratio of sample and extractant picked so that the concentration of vitamins fall into the range of linearity of the calibration curve), the studied material is placed in a light-tight casing, which is mounted on the ultrasonic bath. Extraction spend 15-20 minutes at a temperature of 38-42°C. and Then centrifuged for 10 minutes at 8000 rpm, bring up to the mark in a volumetric flask. The resulting solution was used for chromatographic analysis. Chromatographic separation carried out on a column (250×4 mm with a sorbent Purospher RP-18e (5 µm). Chromatograph conditions were as follows: eluent A - 0.005 M solution of lithium perchlorate pH of 2.5; eluent B - acetonitrile; gradient elution mode from 0 to 26% of eluent B over 14 minutes. The injected volume of 40 ál. The wavelength of detection: UV detector from 0 to 8 minutes 250 nm, 8 to 10 minutes 200 nm, 10 to 12 minutes 230 nm, from 12 to 18 minutes 200 nm; fluorescence detector when the absorption at 270 nm from 0 to 12 minutes at 400 nm (luminescence), from 12 to 18 minutes to 495 nm (luminescence).

Compared the impact of different extraction methods on the degree of extraction of vitamins (for example vitamin B2)

Table 1.
Methods of determination of water-soluble vitaminsTime extrage the Finance, minMethods of extractionThe output of vitamin B2 %
GOST10Magnetic stirrerat 88.1
The method according to Lanovoy et al.20Stirring in the dark86,6
The proposed method15-20In the dark, the ultrasound frequency 35 kHz96,4

From table 1 it is seen that the highest yield of vitamin (96,4%) is achieved using ultrasound, for 15-20 minutes, similar results were obtained for other vitamins. Mechanical mixing and applying a magnetic stirrer to achieve given the completeness of extraction.

Compared the effect of temperature regimes on the degree of extraction of vitamins (for example vitamin B2)

Table 2.
Methods of determination of water-soluble vitaminsTemperatureThe output of vitamin B2 %
GOST heatingof 87.3
The method according to Lanovoy et al.room81,4
The proposed method38-42°C97,2

Table 2 shows that when the temperature rises to 40°C, the yield of the vitamin is increased to 97.2 per cent, and lower temperatures make it difficult to achieve given the completeness of extraction, at a temperature above 42°C is destroyed unstable vitamins (B1, K3), similar results were obtained for other vitamins, so the temperature of 38-42°C is optimal for the conservation and more complete extraction of vitamins premixes.

Separation of the precipitate and the supernatant liquid is carried out by centrifugation. It was found that the mode proposed in the Guest: 5000-6000 rpm for 3 minutes, it is not possible to achieve complete separation of the phases, the proposed regime 8000 rpm for 10 minutes is optimal, as it achieves a more complete separation of the phases.

On the model solutions were experimentally selected conditions chromatographic separation of vitamins concentration of lithium perchlorate (0,4, 0,1, 0,05, 0.005 M) and gradient elution in such a way that one analytical procedure sample possible is Astelit the following vitamins: C, B1, B2, B3, B5, B6, H, B12, K3 - criteria for the separation of two adjacent peaks in all cases is greater than 1. Some characteristics of the chromatographic separation of the vitamins listed in table 3.

Table 3
The characteristics of the chromatographic separation of vitamins
VitaminRetention time, min (n=5, P=0,95)Wavelength detection, nmThe criterion of separation
With UV-detector
3,18±0,10
B54,35±0,092504,8
B16,59±0,072505,0
B38,56±0,062006,3
K310,59±0,092306,3
B1 11,74±0,142302,0
N12,93±0,102002,4
with fluorescence detection, while the absorption at 270 nm
B67,42±0,06400 (luminescence)
B212,70±0,09495 (luminescence)10,4

From table 3 and the chromatogram in figure 1 shows that the concentration of lithium perchlorate 0.005 M and a gradient from 0% to 26% of acetonitrile are optimal for a wide range of vitamins (9).

In the selected conditions set the range of linear dependence of the analytical signal of chromatographic peak area - concentration of vitamins in the solution. For vitamin B1 it was 0.5-20 µg/ml, for B5 - 0.5 to 100 μg/ml for the other vitamins and 0.5-50 µg/ml

On the model solutions evaluated the correctness and precision of the determination of vitamins in the mixture according to the developed methodology. Calculation of concentrations led by calibration curve. The ratio of the concentration of vitamins in the model solution was near what about their ratio premix formulations. The results are presented in table 4.

Table 4.
VitaminEntered, ug/mlFound, ág/mlδ, %W %
B13,002,98±0,29-0,674,0
B210,0010,38±0,363,801,4
B320,0020,14±0,600,701,2
B560,0059,91±0,56-0,150,6
B65,00to 4.98±0,34-0,402,7
K320,0019,59±0,48-2,050,9
N 10,0010,27±0,922,70a 3.9

From table 4 it is seen that the proposed technique improves the efficiency and accuracy of vitamins, because the relative error of quantification (δ) of not more than 5% (modulo), the coefficient of variation is not more than 4%. The developed method has been applied to the analysis of premixes. Chromatogram 1% premix, based on the zeolite is shown in figure 2.

Table 5.
The results of the analysis of premix mineral-based (n=3, P=0,95)
VitaminSpecified in the recipe, ug/gFound, µg/gW %Δ, %*
B1500462±252,17-7,60
B220001892±430,98-5,45
B343504356±1030,96 0,14
B51500015394±6151,612,63
B615001629±58of 1.348,57
K315001602±962,32of 6.73
* the discrepancy between the published data and results.

From figure 2 and table 5 shows that the proposed method of determination of water-soluble vitamins allows you to expand the range defined vitamins from premixes on any basis, while the coefficient of variation less than 3%, the discrepancy between the published data and the results obtained not more than 9% (maximum difference of 15% according to GOST R 50929-96 "Premixes. Methods for determination of vitamins").

Thus, the proposed method of determination of water-soluble vitamins premixes improves accuracy and allows to expand the range defined vitamins to nine.

The method of determination of water-soluble vitamins premixes, including grinding, the capture of sample, extraction with hydrochloric acid, zentrifugenbau is s, the premise of the obtained solution in the volumetric flask, the chromatography was carried out in reversed-phase variant using gradient elution mode, as eluents used solution of lithium perchlorate and acetonitrile, characterized in that the extraction is carried out with ultrasound for 15 to 20 minutes at a temperature of 38-42°C, centrifuged 10 min at 8000 rpm, a solution of lithium perchlorate is used in a concentration of 0.005 M, gradient elution from 0% to 26% acetonitrile for 14 minutes



 

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