Separation of caffeine

The effect of concentration of cationic (cetylpyridinium chloride, CPC), anionic (sodium dodecylsulfate, SDS) and nonionic (Twin-80) surfactants as well as effect of pH value on the characteristics of TLC separ ation has been investigated. The best separ ation of three components has been achieved with 210 M CPC and LIO M Twin-80 solutions, at pH 7 (phosphate buffer). Individual solution of SDS didn t provide effective separation of caffeine, theophylline, theobromine, the rate of separ ation was low. The separ ation factor and rate of separ ation was increase by adding of modifiers - alcohol 1- propanol (6 % vol.) or 1-butanol (0.1 % vol.) in SDS solution. The optimal concentration of SDS is 210 M. 

Hubert, P., Vitzthum, O., Separation of caffeine from supercritical solutions,... 

Furthermore, supercritical CO2 does not behave as merely a mixture of liquid and gaseous CO2, but often exhibits an exceptional ability to solvate molecules in a specific way. The removal of caffeine from coffee relies on the chromatographic separation of caffeine and the other organic substances in a coffee bean supercritical fluid chromatography is a growing and exciting branch of chemistry. 

Fig. 3.138. Electropherogams showing the separation of caffeine (1), aspartame (2), brilliant blue FCF (3), green S (4), sorbic acid (5), benzoic acid (6), saccharin (7), acesulfame K (8), sunset yellow FCF (9), quinoline yellow (10), carmoisine (11), ponceau 4R (12), black PN (13), using 20 mM carbonate buffer, pH 9.5 containing (a) no SDS, (b) 50 mM SDS, (c) 75 mM SDS. A 48.5 X 50 /tm I.D. fused-silica capillary was used and absorbance was measured at 200 nm. Reprinted with permission from R. A. Frazier et al. [184],...

Figure 8.10—Electrophoretic separation of three species a, h and c. in this example, the electro-osmotic flow moving towards the cathode carries all charged and neutral species. Negatively charged species, although attracted towards the positive pole (or anode) cannot overcome the electro-osmotic flow and thus move towards the cathode. Separation of caffeine (c) from aspartame (a-) and benzoate (b ) in a Diet Cola sample. The presentation of data is in the form of a 3-D electrophoregram. (Reproduced by permission of TSP.)...

Figure 0-4 Principle of liquid chromatography, (a) Chromatography apparatus with an ultraviolet absorbance monitor to detect analytes at the column outlet. (fc>) Separation of caffeine and theobromine by chromatography. Caffeine is more soluble than theobromine in the hydrocarbon layer on the particles in the column. Therefore, caffeine is retained more strongly and moves through the column more slowly than theobromine.

A further method separates the extracted substances by absorption. Basic for this method is that there should be a high solubility of extracted substances in the absorption material, and that the solubility of absorption substance in the circulation solvent should be as low as possible. Further, the absorption material must not influence the extract in a negative way and a simple separation of extract and absorption material has to be available. An ideal absorption material is therefore a substance which is present in the raw material. Most plant-materials contain water, which can act as a very successful absorption material. An ideal example is the separation of caffeine for the decaffeination of coffee and tea. On the one hand, water has a low solubility in CO2, and on the other, water-saturated CO2 is necessary for the process. The extracted caffeine is dissolved into water in the separator and caffeine can be produced from this water-caffeine mixture by crystallization. One advantage of this separation method is that the whole process runs under nearly isobaric conditions. 

H. Figure 13-5 shows an example chromatogram for the separation of caffeine, saccharin, and benzoate. Figure 13-6 shows an example... 

Soluble 1 in 4 of hot water, dissociating on further dilution with the separation of caffeine on cooling which redissolves in about 32 of water soluble 1 in 25 of ethanol. 

Figure 18-7. Effect of temperature on the separation of caffeine derivatives on a Hypercarb column (1 mm x 100mm). (a) Column at 100°C, mobile phase acetonitrile (b) Colnmn at 180°C, mobile phase water/acetonitrile 70/30. Samples 1, hypoxantine 2, theobromine 3. theophylline 4, caffeine 5, P-hydroxyethyltheophylline. (Reproduced from reference 35, with permission.)...

Tokunaga Y, Fujii T, and Nakamura K. Separation of caffeine from supercritical carbon dioxide with a zeoUte membrane. Biosci. Biotech. Biochem. 1997 61(6) 1024—1026. 

Ion Exchange Adsorption Process. Supercritical fluid extracts of Crotalaria spectabilis contain monocrotaline, a basic alkaloid, and non-polar lipid material. In the separation of caffeine from coffee, Zosel (3) recommended separation of the caffeine from the fluid phase by either adsorption onto activated carbon or absorption into liquid water. Activated carbon adsorption would be undesirable in the present case because the lipids would also be adsorbed and because desorption from activated carbon is quite difficult. Liquid water would absorb... 

Figure 8.10 Electro-kinetic separation of three species a, and c. Left, The electro-osmotic flow carrying all of the charged or neutral species along with it, is directed towards the cathode. The negative species though attracted hy the positive pole cannot overcome the electro-osmotic flow and are therefore displaced towards the cathode. Right, separation of caffeine c and of the anions of aspartame a and of henzoate h from a sample of DIET COLA. Presentation in the form of a 3D electropherogram (reproduced courtesy of TSP).

To start the separation of caffeine from the aqueous solution, a small portion of the solution from a water vessel is pumped to another vessel where it is heated to about 100... 

The separation of caffeine from coffee by entrainer sublimation... 

Parra, R Limon, A. Ferre, S. Guix, T. Jane, F. High-performance liquid chromatographic separation of caffeine, theophylline, theobromine and paraxanthine in rat brain and serum. J.Chromatogr., 1991, 570, 185-190... 

Specific thin-layer-chromatographic procedures for the separation of caffeine have been published.One of these has been developed for the student... 

The molecular recognition capabilities of polyelectrolyte multilayers have also been investigated by Laschewesky [55], while imprinted films have been grown on membrane surfaces in approaches similar to the phase inversion method for preparing a membrane imprinted with theophylline. Wang et al. [56] adopted an acrylonitri-le/dithiocarbamoyl-methylstyrene copolymer (Fig. 16) to effect separation of caffeine from the theophylline-imprinted membrane. 

Gas chromatography The AOAC method for the analysis of caffeine by GC uses a packed glass column, 6 ft ( 180 cm) in length by 4 mm ID, packed with 10% DC-200 oil on 80-100 mesh Gas Chrom Q, using nitrogen carrier gas and a thermionic potassium chloride detector. The injector temperature is 220°C, the column temperature is 190°C, and the detector temperature is 220°C. A wide variety of column-packing materials and detection modes can be used. For example, separation of caffeine, theophylline, and theobromine can be achieved with... 

After the twofold development (HTpSPE), the target zones—visible by Sudan II—were easily eluted by the TLC-MS interface into autosampler vials to perform the offline HTpSPE-HPLC-MS(/MS) analysis. The direct transfer of the eluates by the online HTpSPE-HPLC-MS(/MS) hyphenation was additionally possible, but due to the poor time efficiency not routinely applied. The cleanup effect of HTpSPE, especially attributed to the separation of caffeine, was easily demonstrated by HPLC-MS analysis in the full-scan mode (Eigure 10.13). 

---