Caffeine precipitation

COPLAND E L, CLIFFORD M N and WILLIAMS c M (1998) Preparation of (-)-epigallocatechin gallate from commercial green tea by caffeine precipitation and solvent partition . Food Chem, 61, 81-7. 

The soft drink is discarded, and the CHCI3 in the pot evaporated. The caffeine is washed out of the pot with water, 1 1 HCI is added, and the caffeine precipitated with phosphomolybdic acid. The precipitate is digested about 20 minutes. The precipitate is filtered and then washed with 1 9 HCI. The precipitate is dissolved off of the flitted glass with acetone, and the solution diluted to 25 mL. The caffeine is determined spectrophotometrically at 440 nm vs. an acetone reference. 

The solvent power of a supercritical fluid can usually be increased by increasing the pressure. The decaffination of coffee provides a simple commercial example (47,48). Here, supercritical carbon dioxide is contacted with ground coffee. The caffeine preferentially dissolves in the carbon dioxide, which is subsequently moved to another location. Then, when the pressure is lowered, the caffeine precipitates out, and the cycle repeated. 

According to Daoust small amounts of caffeine can be determined by precipitation as phosphomolybdate and solution in acetone for colorimetric measurement. Aspirin or phenacetin do not interfere but the reaction is not specific for caffeine. Although precipitation of larger amounts may be convenient, a 3 mg aliquot of caffeine precipitated in a volume of 25 ml is most suitable for colorimetric measurement a large excess of precipitating reagent should be avoided. 

Until recently, the principal method of decaffeinating coffee was to extract the caffeine with a solvent, such as methylene chloride (CH2CI2). This solvent is objectionable because it is hazardous in the workplace and difficult to completely remove from the coffee. Now, supercritical fluid CO2 is used. In one process, green coffee beans are brought into contact with CO2 at about 90 °C and 160 to 220 atm. The caffeine content of the coffee is reduced from its normal 1% to 3% to about 0.02%. When the temperature and pressure of the CO2 are reduced, the caffeine precipitates and the CO2 is recycled. 

Instant tea produced as described above will dissolve completely in hot water but not in cold water, as the caffeine-polyphenol complexes are insoluble under those conditions. Since virtually all instant tea manufacture in the U.S. is for iced tea preparation, process modification is required. This initial extract may be cooled to 5 to 10°C and the cold water insoluble material or cream be allowed to precipitate. Under these conditions, 20 to 35% of the extract solids may be separated by centrifugation. The supernatant solids will reconstitute in cold water after concentration and drying.105 It is also possible to process the cream to make a portion of it compatible with the product and thereby retain the caffeine and some polyphenolic components that are present in this fraction.106 Commercial use of the enzyme Tannase, which removes gallic acid from gallated tea polyphenols107 and reduces cream formation108 can be used to reduce cream losses and manufacture instant teas retaining more of the natural polyphenol content. 

The alternative approach draws form the experience of coffee decaffeination. The currently practiced process is carried out on a massive scale using scC02 to extract the caffeine from the coffee beans. The caffeine is not precipitated from the scC02 by decompression, but is extracted into water from which it can be separated. The great advantage of this process is that it can be operated at essentially constant pressure and... 

The role of caffeine in migraine headaches is due to its vasoconstrictor effects. Caffeine is used in combination with ergotamine for migraine (Sawynok 1995 Sargent et al. 1988). However, discontinuation or missing a dose of caffeine after chronic use can precipitate headaches (Fennelly et al. 1991 Couturier etal. 1992). 

Once chronic insomnia has developed, it hardly ever spontaneously resolves without treatment or intervention. The toll of chronic insomnia can be very high and the frustration it produces may precipitate a clinical depression or an anxiety disorder. Insomnia is also associated with decreased productivity in the workplace and more frequent use of medical services. Einally, substance abuse problems may result from the inappropriate use of alcohol or sedatives to induce sleep or caffeine and other stimulants to maintain alertness during the day. 

After terminating the coupling reaction with ascorbic acid, reaction mixture clarified by precipitating protein with ethanol Turbidity decreased by final addition of caffein, sodium benzoate, and Teepol micromethod After the coupling reaction with ascorbic acid is terminated, azo color is extracted and read low blank the extract can be applied directly to a thin-layer plate and be separated rapidly to determine the ratio BMC BDC Micro versions assay artificially activated enzyme... 

The ultraviolet spectra of the precipitate can be seen in Figure 2 along with the spectra of pure caffeine and pure pyrogallol solutions. With such low concentrations it is assumed that the caffeine and pyrogallol are completely dissociated and that their ultraviolet spectra will be additive. Hence, if we let the ratio of pyrogallol with respect to caffeine be 1 P, then the extinction coefficient of the complex is ... 

Thus, we have a 1 1 complex. (The same result is observed when the complex is precipitated from a non-1 1 mixture of caffeine and pyrogallol (e.g., 1 2 mixture). 

The HC1 would react with the free base to form the water-soluble, but diethyl ether-insoluble, hydrochloric acid salt of caffeine. With no water available to dissolve this material, it precipitates out of the diethyl ether as a solid that may be collected by filtration. 

The group of Ciardelli prepared MIP nanoparticles imprinted with theophylline or caffeine by precipitation polymerisation and coated them onto a poly-MMA-co-AA membrane (Fig. 18) [217, 255, 256]. 

Mosbach and co-workers developed a method to prepare molecularly imprinted polymers by precipitation polymerization [24]. They started from a dilute, homogenous solution of the monomer methacrylic acid (MAA) and the crosslinker trimethylolpropane trimethacrylate (TRIM) or ethylene glycol dimethacrylate (EGDMA). The polymer formed in the presence of the template molecule 17/1-estradiol, theophylline, or caffeine contained a high proportion of discrete spheres of diameter less than a micron. Because the effect of coalescence becomes predominant with higher solid content of the reaction mixture, this approach is limited to solid contents of typically <2 wt%. 

Caffeine 2. Chaste tree 3. Green tea 4. Plantain 1. Lithium 2. Phenothiazines (e.g. chlorpromazine, promazine, levomepromazine, pericyazine, pipotiazine, fluphenazine, perphenazine, trifluphenazine) 3. Clozapine L blood lithium levels with 1 clinical effects. 1 effects of phenothiazines Unknown mechanism (caffeine) Contains dopamine agonists (chaste tree) Induction of metabolizing enzymes (green tea may induce CYP1A2, which metabolizes clozapine) l absorption from the gut (plantain may l absorption of lithium) Be aware. Caffeine withdrawal may precipitate lithium toxicity, so avoid sudden caffeine withdrawal. Avoid concomitant use if possible... 

Excess caffeine can stimulate the CNS, which can worsen psychosis and thus interfere with the effects of neuroleptic drugs (54). Neuroleptic drugs can precipitate from solution when mixed with coffee or tea (55), but the clinical significance of this interaction is unknown (56). 

Of more than pure chemical interest is the recent report concerning the implications of consumption of caffeine in common beverages. Although tea and coffee contain approximately the same amount of caffeine (2—5%), the former also contains adenine, which is thought to neutralize the action of caffeine. The presumed reason that children are allowed to drink chocolate and cocoa is that these contain only 0.25% of caffeine The effects of certain precipitating agents and of variation of the pH during extraction procedures on caffeine and related alkaloids have been studied. ... 

The lowering of pressure to precipitate the extract is not always necessary. For example, in the case of decaffeination of coffee beans, water can be used to extract caffeine from the COi/caffeine mixture, as caffeine is readily soluble in water (Fig. 3). 

Reverchon E, Donsi G, Gorgoglione D. Salicylic acid solubilization in supercritical CO2 and its micronization by RESS. J Supercrit Fluids 1993 6 241-248. Subra P, Boissinot P, Benzaghou S. Precipitation of pure and mixed caffeine and anthracene by rapid expansion of supercritical solutions, Proceedings of the 5th meeting on Supercritical Fluids. Vol. 1. Perrut M, Subra P, ed. 23-25 March, Nice, France, 1998 307-312. 

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