Method of extracting caffeine from aqueous solution

FIELD: chemistry.

SUBSTANCE: to extract caffeine from an aqueous solution, a water-salt solution of caffeine with pH 11.0±1.0 is prepared using saturated potassium carbonate solution as a salting-out agent; caffeine is extracted until establishment of phase equilibrium for 7-10 minutes with a solution of a solvotropic reagent in ethyl alcohol with concentration of 0.85-0.90 mol/dm3 with volume ratio of the water-salt solution of caffeine to the extractant of 5:1; the water-salt phase is separated from the organic phase and analysed by UV spectrophotometry at wavelength of 272 nm. Concentration of caffeine in the aqueous solution is determined from a calibrated curve.

EFFECT: method enables to achieve high coefficient of distribution of caffeine with one-fold extraction with a solution of a solvotropic reagent in ethyl alcohol, and virtually complete extraction of caffeine from the water-salt solution.

1 ex

 

The invention relates to analytical chemistry and pharmaceutics and can be used for extraction of purine alkaloids from aqueous media with a view to their subsequent definitions.

The closest in technical essence and the achieved effect is sorption of caffeine on supersewn polystyrene [Andreeva EJ, Dmitrienko YEAR, Y.A. Zolotov. Sorption of caffeine and theophylline on supersewn polystyrene. News. Mosk. Univ. Ser. Chemistry. 2010. T. No. 1].

The technical problem of the invention is to design the extraction system in order to achieve high distribution coefficients of caffeine and almost complete removal from aqueous hydrophilic solvent with the use of allotropes reagent.

The solution of the technical problem of the invention is achieved by the proposed method for the extraction of caffeine from aqueous solutions as allotropes reagent is applied dibutyl phthalate (DBP), the extractant is ethanol, visivel - potassium carbonate. Prepare a solution of DBP in ethyl alcohol with a concentration of 0.8-0.9 mol/DM3this solution is extracted caffeine from aqueous salt solution that has a pH of 11.0±1,0 due to the use as vicariates potassium carbonate. The addition of caffeine Pharmacopoeia purity, taken on an analytical balance, placed in a chemical from the akan capacity 50 cm 3, dissolved in a small volume (2-3 cm3) distilled water, after complete dissolution of the sample (5 min) the solution is transferred into a volumetric flask with a capacity of 100 cm3and bring to the mark with saturated potassium carbonate solution, extracted caffeine solution of DBP in ethyl alcohol to the resulting solution of caffeine add a solution of DBP in ethyl alcohol with a concentration of 0.9 mol/DM3when the volume ratio of water-salt solution of caffeine and extractant 5:1, is extracted on vibromaster to establish the interfacial equilibrium (7-10 min), after separation system (5-7 min) water-salt solution is separated from the organic phase and analyzed by means of UV-spectrophotometry to measure the optical density of a water-salt solution by UV-spectrophotometer in a quartz cuvette with a thick light-absorbing layer of 1 cm at a wavelength of 272 nm, build a graph of optical density of a water-salt solution with concentration of caffeine, according to the schedule, find the concentration of caffeine in aqueous solution.

Calculate the distribution coefficient (D) and the degree of extraction of caffeine (R, %) by the formulas:

D=cocin,R=DD+ f100%,

where c0and cin- the concentration of caffeine in the organic and aqueous phases, f is the ratio of the equilibrium volumes of aqueous and organic phases.

The technical result of the invention consists in achieving a high distribution coefficient of caffeine (up to 400), almost full (98,8%) extraction of caffeine from aqueous solution of DBP in ethanol in the presence of potassium carbonate.

The implementation of the method is illustrated by the following example. Prepare a water-salt solution of caffeine, which has a pH of 11.0±1,0 due to the use as vicariates saturated solution of potassium carbonate, for which a portion of the caffeine Pharmacopoeia purity, taken on an analytical balance, placed in a chemical beaker 50 cm3, dissolved in a small volume (2-3 cm3) distilled water, after complete dissolution of the sample (5 min) the solution is transferred into a volumetric flask with a capacity of 100 cm3and bring to the mark with saturated potassium carbonate solution, extracted caffeine solution of DBP in ethyl alcohol to the resulting solution of caffeine add a solution of DBP in ethyl alcohol with a concentration of 0.9 mol/DM3when the volume ratio of water-salt solution of caffeine and extractant 5:1, is extracted on vibromaster to have is Stanovlenie interfacial equilibrium (10 min). After stratification system (5-7 min) water-salt phase is separated from the organic and analyzed by means of UV-spectrophotometry. Measure the optical density of a water-salt solution by UV-spectrophotometer in a quartz cuvette with a thick light-absorbing layer of 1 cm at a wavelength of 272 nm build a graph of optical density of a water-salt solution with concentration of caffeine, according to the schedule, find the concentration of caffeine in aqueous solution.

The distribution coefficient (D) and the degree of extraction of caffeine after the first extraction (R, %) was calculated according to the formula:

D=cocin,R=DD+f100%,

where c0and cin- the concentration of caffeine in the organic and aqueous phases; f is the ratio of the equilibrium volumes of aqueous and organic phases.

The concentration of caffeine in aqueous solution are found by calibration curve according to the optical density of aqueous solutions on the concentration of caffeine.

The organic phase passes, 98.8% of the caffeine from its original content in the sample solution, the distribution coefficient is 400,5.

It is to be seen from the example, achieved a high distribution coefficient (400,5) and almost full (98,8%) extract caffeine solution of DBP in ethanol, at a ratio of volumes of a water-salt solution and the extractant 5:1 and applied as vicariates potassium carbonate. Duration analysis 30-35 minutes

When using water-salt solutions of caffeine made with another vysalivatel or proposed vysalivatel, but other concentrations, as well as the application of other extractants and ratios of the volumes of the phases, the degree of extraction of caffeine is much lower than achieved in the following example.

The proposed method for the extraction of caffeine from aqueous media allows you to reach high values of distribution coefficient (up to 400,5) and to reach almost full (98,8%) extraction of caffeine from aqueous salt solution, is characterized by expresspost (duration analysis 30-35 min) and can be applied in the analysis of aqueous media containing caffeine.

The method of extraction of caffeine from an aqueous solution comprising preparing a solution of caffeine by dissolving in a saturated solution of vicariates, extraction and analysis of the equilibrium aqueous phase, characterized in that the extractant solution using allotropes reagent in ethyl alcohol with a concentration of 0.85-0.90 mol/DM3why prepare a water-SOLEV the th solution of caffeine with a pH of 11.0±1,0 due to the use as vicariates saturated solution of potassium carbonate, extracted caffeine within 7-10 min solution allotropes reagent in ethanol in the volume ratio of water-salt solution of caffeine and extractant 5:1, separate water and salt from the organic phase and analyzed by means of UV-spectrophotometry at a wavelength of 272 nm, calibration curve to find the concentration of caffeine in aqueous solution.



 

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