Method of extracting caffeine from aqueous solution
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.
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:
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:
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.
SUBSTANCE: method of determining content of ascorbic acid in solutions, plant and animal material, involving extraction of ascorbic acid from analysed samples with HCl solution or some other acid, where 1 ml of the obtained extract is mixed with 1 ml of 1 mM iron chloride solution and 1 ml of 3 mM potassium ferricyanide solution, stirred, transferred into the cuvette of a spectrophotometer; optical density is measured at 693 nm and content of ascorbic acid in the analysed sample is calculated from a calibration curve.
EFFECT: method is objective and highly sensitive.
1 tbl, 1 ex
SUBSTANCE: invention describes a method for measuring the water content in tablet mass in tablet production by coulometric titration which is based on a reaction of water of an examined sample with a iodine electrically generated coulometric titrant which is formed by electrolysis of organic or non-organic iodide (e.g. CH3I or KI), being a part of a ground electrolyte at constant current 50 mA for a period of time determined by biopotentiometry and shown by an end-point titre achieved; the water content (X, g) in an aliquot of the examined sampled is calculated by formula, and simultaneously water is measured in a solvent, and common formulas are used to measure the water content in the tablet mass.
EFFECT: method is characterised by expressivity, experimental simplicity, sensitivity and accuracy.
2 tbl, 1 dwg, 1 ex
SUBSTANCE: method involves measuring emf of the analysed sample, which is brought to pH 5 with hydrochloric acid with addition of calcium chloride solution with concentration of 1 mol/l in ratio of 5:1, using a silver chloride electrode and a calcium selective electrode, and then finding concentration of calcium using a calibration curve. The method enables to determine content of calcium in the range of 0.004-4 g/l.
EFFECT: method enables to conduct analysis without preliminary sample preparation, without spending time on titration, without using indicators and without spending on expensive equipment.
1 tbl, 5 ex
SUBSTANCE: invention can be used for photoelectrocolorimetric determination of sulphanilamide preparations - streptocide, sulfadimezin, ethazol, sulfalene, phtalazol, sulfathiazole, sulfadimethoxine, sulfamonomethoxine in factory main laboratories, in analytical laboratories, in biochemical laboratories of clinics and in forensic chemical laboratories. The method involves dissolving a medicinal agent in 0.1M hydrochloric acid solution in case of sulfalene and phtalazol or 0.1M alkali solution in case of streptocide, sulfadimezin, ethazol, sulfathiazole, sulfadimethoxine or sulfamonomethoxine, holding on a hot water bath while stirring until complete dissolution, cooling and adding the same solution to the mark, further treatment of an aliquot part of the prepared solution with 0.1M potassium hydroxide solution (only in case of phtalazol and sulfalene) and 1% alkaline solution of sodium nitroprusside, 3% hydrogen peroxide solution and subsequent photoelectrocolorimetry of coloured solutions at wavelength of 670 nm.
EFFECT: high sensitivity, selectivity and accuracy of determining medicinal substances in pharmacopoeial preparations.
2 cl, 9 dwg, 2 ex
SUBSTANCE: invention describes a method of determining concentration or content of ascorbic acid in liquid drug formations, involving preparation of doses of an analysed sample and a standard sample, wherein 0.6 ml of a sodium phosphate buffer (0.05 mol/l, pH 8,3), 0.1 ml of tetramethylene diamine solution (0.05 mol/l) in a sodium salt of ethylenediamine tetraacetic acid (0.2 mmol/l), 0.1 ml of the analysed sample and 0.2 ml of riboflavin solution (0.034 mmol/l) are successively fed into a chemiluminometer cell; the same volume of distilled water is added to the control sample; further, the reaction is initiated by irradiation with a visible light lamp (100 W) at a distance of 20 cm for 60 s; 10 s before irradiation time expires, 0.1 ml of luminol solution (0.25 mmol/l) is added; after irradiation, the cell holder is moved into the operating position in front of the photocathode of a photomultiplier (about 1 s) in a biochemiluminometer and the chemiluminometer flash is detected; concentration of ascorbic acid in the mixture or content thereof is calculated in the same units it was recorded using a formula.
EFFECT: method is characterised by optimum rapidness, easy preparation of samples for analysis and high reproducibility and accuracy.
4 ex, 1 tbl, 1 dwg
SUBSTANCE: samples or objects in vivo with or without a drug preparation, as well as a reference objects with the stable optical properties are exposed to optical (laser) radiation either simultaneously, or one by one. The samples may include a patient's biomaterial substrate taken in vivo and/or in vitro. The measured objects in vivo with or without the drug preparation may be represented by areas of inflammation, injury or other pathological tissue, mucosa etc. containing the test drug preparation introduced into the body, as well as intact or unaffected areas of tissue, possibly asymmetrical with the involved ones. When the sample and/or objects in vivo with or without the drug preparation, and/or the reference object are exposed, time dependences of their fluorescence and/or Raman scattering and/or other optical response are measured. Said process (cycle) of measurements is interrupted and repeated with the same or another above-described samples and/or objects in vivo taken from the same or another body and/or in vitro and/or with no biomaterial. The drug preparation is chosen by a degree of decreasing standard fluorescence intensity of the objects with the drug preparation.
EFFECT: higher clinical effectiveness.
10 cl, 1 tbl, 4 dwg
SUBSTANCE: method of detecting lysine in a mixture of α-amino acids, except a mixture containing cysteine and proline, involves preparation of an acetate-ammonia buffer solution with pH 3.06 to which is added 0.1% lysine solution in such an amount that its content in the final solution ranges from 0.0004 to 0.008%; 0.2% aqueous ninhydrin solution in such an amount that content of ninhydrin in the final solution ranges from 0.01 to 0.03%; heating the obtained solution on a water bath at 95-105°C for 15-25 minutes; adding cetylpyridinium chloride in an amount which ensures its content in the solution in a concentration after critical micelle concentration of 0.1-0.4%; measuring the absorption spectrum of the obtained solution; detecting lysine in the solution based on the presence of a maximum at wavelength λmax=480 nm.
EFFECT: simpler, faster and cheaper procedure of determining lysine while maintaining high metrological parameters of the determining method.
1 tbl, 11 dwg
SUBSTANCE: method for polysaccharide analysis in herbs of Violet species involving grinding of raw materials, water extraction of a polysaccharide complex when heated, addition of an agent, filtration and polysaccharide quantification by formula, differs by the fact that the raw material is Viola uniflora herb; water extraction lasts for 1 hour in ratio of the raw material : the extractant as 1:50; the extract is filtered, and the filtrate is added with 8% hydrochloric acid in ratio 1:1; the mixture is kept for 2 hours on a boiling water bath, then cooled and reduced to pH=6.5-7.0; thereafter the mixture is added with 1% picric acid and 20% sodium carbonate in ratio 1:3; the prepared mixture is kept on a water bath for 30 minutes, then filtered; it is followed by spectrophotometric analysis of the filtrate in a tray of the absorption layer thickness of 1 am at wave length λ=460±2 nm, while polysaccharides are quantified at a glucose basis by formula.
EFFECT: method enables assessing the quality of medical plants by quantifying accurately polysaccharides contained in herbs of Violet species.
2 tbl, 1 ex
SUBSTANCE: invention describes a method for detecting nitrofuran, pyrazole, isonicotinic acid, thioamino acid derivatives in dosage forms consisting in preliminary transforming the analysed preparation into a liquid form, placing it in a cell containing a certain amount of generated iodine prepared by exposing the reaction mixture consisting of 0.5 M potassium iodide, a buffer solution and a sentitiser - sodium eosinate, to a stabilised light source, measuring current intensity in the cell, and once current stability reached, air-blowing the solution in the cell for 1-2 min, exposing to light and measuring a generation time for iodine loss compensation, determining an amount of the analysed preparation as shown by a calibration diagram of current intensity and iodine generation time.
EFFECT: simplified method, reduced length of the analysis, higher accuracy and wider detection limits of organic substances in the pharmaceutical preparations.
2 ex, 2 tbl, 2 dwg
SUBSTANCE: invention describes a method for determination of nitrogen in an ozonised perfluoridecarbon emulsion by photometric measurement of iodine recovered by a reaction of nitrogen of the ozonised emulsion and a potassium iodide solution with starch; the determination process is preceded by preparing a reaction solution containing potassium iodide and starch to be used to prepare sample and calibration pre-solutions containing the equal proportions of potassium iodide and starch; the sample pre-solution is added with a specific amount of ozonised perftoran, while the calibration pre-solutions are added with the same amount of non-ozonised perftoran and standard iodine in potassium iodine in the amount required to draw a calibration diagram; the prepared solutions are kept in a dark plate at temperature 20°C; the solutions are measured in a photocolorimeter or a spectrophotometer at wave length 610 nm following the time variations of optical density until the curves of the calibration and sample solutions occurs to match; a calibration diagram is drawn, and nitrogen is calculated in the sample emulsion.
EFFECT: invention enables determining nitrogen in aqueous-organic emulsions thereby enhancing its analysis in complex, polycomponent heterogenic media.
1 ex, 3 dwg
SUBSTANCE: three samples of a letter are obtained and analysed, one of which is extracted with a solvent and subjected to UV spectrophotometry right away; the second is analysed 30 days layer; the third is analysed 60 days after analysing the first sample; the second and third samples are extracted and subjected to UV spectrophotometry in the same conditions as the first sample; quantitative comparison of the results of UV spectrophotometry of the three samples is carried out based on the ratio of optical densities in the region of peaks (330-1100 nm) of dyes per unit length of the line of each sample in intervals of 1 and 2 months to obtain the behaviour of ageing of the manuscript, wherein ageing takes place in "natural" conditions with optimally permissible temperature, relative humidity and air speed in accordance with GOST 30494-96.
EFFECT: simplicity, high accuracy, guaranteed reproducibility and high reliability of determining ageing.
SUBSTANCE: described is method of quantitative determination of metronidazole by spectrophotometry of determined substance and standard sample of comparison, and as solvent for preparing determined solution applied is 0.1M solution of hydrochloric acid, spectrophotometry is carried out at wave length 276 nm, as sample for comparison applied is benzoic acid or phenolphthalein and calculation is carried out by formula.
EFFECT: method makes it possible to increase repeatability of determination results, reduce cost, labour consumption, analysis error, standardise analysis methods.
SUBSTANCE: device for determining overall unsaturation of organic compounds has an oxygen or air dosing unit, an electrodischarge ozoniser, a bubbling reactor, a spectrophotometric ozone analyser. The spectrophotometric analyser has two photosensors fitted with operational amplifiers. One of the photosensors is designed to detect concentration of ozone at the output of the ozoniser, and the second is designed to detect ozone concentration at the output of the bubbling reactor. In the absence of ozone, voltage signals from both photosensors are equal and after operational amplifiers, said voltage has a value V0. The device also has a unit for stabilising ozone concentration consisting of said photosensor fitted at the output of the ozoniser, a comparator which compares the voltage signal at the output of the operational amplifier connected to said photosensor with a given value Vc, and a latching transistor controlled by the comparator and connected in the power supply circuit of the ozoniser.
EFFECT: stability of ozone concentration, high measurement accuracy and wider measurement range during analysis using an ozone-air and an ozone-oxygen mixture.
2 cl, 1 dwg
SUBSTANCE: invention refers to a method of analysing oligosaccharides being components of low molecular weight heparins and very low molecular weight heparins in blood plasma. A method of analysing β-unsaturated oligosaccharides in blood plasma. Application of the method for quantitative analysis of enoxaparin, octaparin, bemiparin or tinsaparin. Application of the method for quantitative analysis of octasaccharides (versions).
EFFECT: more adequate oligosaccharide analysis.
15 cl, 2 dwg, 2 tbl, 2 ex
SUBSTANCE: solutions of a substance to be determined and a reference sample are prepared. 0.1 M sodium hydroxide is used as a solvent for preparing the analysed solutions. Potassium chromate or potassium ferricyanide is used as a reference sample. The optical density of the solution of the analysed substance and the reference sample of potassium chromate or potassium ferricyanide is measured by a spectrophotometre at wave length 264 or 298 nm respectively. The results are calculated by formula with an introduced conversion factor.
EFFECT: higher reproducibility of results of determination and reduced analytical error.
SUBSTANCE: solution of the analyte and comparison sample are prepared. The solvent used for preparing the test samples is 0.1 M hydrochloric acid solution. The comparison sample used is potassium ferricyanide or benzoic acid. Optical density of the solution of the analyte and comparison sample of potassium ferricyanide or benzoic acid is measured on a spectrophotometre at wavelength 266 nm. Results are calculated using a formula by entering a conversion coefficient into the formula.
EFFECT: method increases reproducibility of measurement results, reduces cost, labour input, analytical error and enables unification of the analysis method.
SUBSTANCE: solution of substance to be defined and a sample solution for comparison are prepared. As a diluent for the preparation of the test solutions 0.1 M solution of hydrochloric acid is used. As a sample for comparison yellow dimethyl is used. Optical density of solution of substance to be defined and of yellow dimethyl sample for comparison are measured by spectrophotometer at a wavelength of 318 nm. The results are calculated according to the formula with a conversion coefficient.
EFFECT: improving of results reproducibility; reducing of cost, complexity and analysis errors.
SUBSTANCE: method of determining quality of Iceland spar crystals for making polarisers involves measurement of the optical density spectrum of the crystal in the wavelength range from 220 to 400 nm in plane-polarised light. The electric vector of the plane-polarised light is parallel to the optical axis of the crystal. At least two opposite faces of the crystal, parallel to its optical axis, are polished, and the optical axis of the crystal is perpendicular to the incident light. The positions of maximums of the absorption band are determined, as well as the corresponding optical density values, and the quality class of the crystalline material is determined as follows: 1st class - not above 0.31 cm-1, 2nd class - not above 0.35 cm-1, 3rd category - not above 0.45 cm-1.
EFFECT: more accurate control of light absorption of crystalline material for making polarisers.
5 dwg, 1 tbl, 1 ex
SUBSTANCE: present invention refers to analytical chemistry and can be used for quantative determination of methionine in water solutions by spectrophotmetric method. The method includes the preparation of standard methionine solutions, determination of optical density at characteristic wavelength, plotting of the calibration function for standard methionine solutions (optical density against concentrations at characteristic wavelength), determination in the analysed methionine solution of the optical density and methionine concentration according to optical density at characteristic wavelength using the calibration function. The determination of the characteristic wavelength is implemented in ultraviolet spectral region according to the differential absorption in coordinates λ=f(ΔA) whereat ΔA=Afollowing-Aprevious.
EFFECT: enhancing of determination reliability, accuracy and selectivity as well as simplifying and time decrease of the determination.
SUBSTANCE: invention relates to the field of medicine and can be used in control and analytic laboratories for standardisation and control of medication quality. Solutions of substance to be determined and comparison sample are prepared. As solvent for preparation of tested solutions 0.1 M solution of hydrochloric acid is used. As comparison sample phenolphthalein or benzoic acid is used. Optical density of solution of substance to be determined and comparison sample of phenolphthalein or benzoic acid are measured by spectrophotometer. Calculation of results is carried out by formula by introducing to it scaling factor. The method allows for increasing sensitivity of analysis, reproducibility of results of determination, reducing toxicity, labour-intensiveness and analysis error, unifying analysis technique.
EFFECT: increase in analysis sensitivity and reproducibility of results of determination, unification of analysis technique.
FIELD: process engineering.
SUBSTANCE: invention relates, primarily, to vibration extraction column to be used in hydrometallurgy, petroleum radiochemical and other industries. Proposed method comprises adjustment of dispersion-forming initial water and extraction agent solution flow rates, adjustment of phase interfaces, estimation of disperse phase delay in column by measuring pressure difference and adjustment of column load vibration intensity by varying vibration frequency. Note here that disperse phase drop mean diameter is measured and compared to preset value. Originated mismatch is used to very load vibration intensity by adjusting vibration rate and amplitude. Phase boundaries are adjusted by discharging solid phase from column bottom.
EFFECT: higher efficiency of extraction, stable and efficient column operation.
2 cl, 1 dwg, 1 ex