Caffeine evaporation

In some cases, the solids themselves are subjected to extraction by a solvent. For example, in one process used to decaffeinate coffee, the coffee beans are mixed with activated charcoal and a high-pressure stream of supercritical carbon dioxide (carbon dioxide at high pressure and above its critical temperature) is passed over them at approximately 90°C. A supercritical solvent is a highly mobile fluid with a very low viscosity. The carbon dioxide removes the soluble caffeine preferentially without extracting the flavoring agents and evaporates without leaving a harmful residue. 

Figure 5.8 shows such a system we call it a Soxhlet apparatus. Solvent is passed continually through a porous cup holding the ground coffee. The solvent removes the caffeine and trickles through the holes at the bottom of the cup, i.e. as a solution of caffeine. The solvent is then recycled solvent at the bottom of the flask evaporates to form a gas, which condenses at the top of the column. This pure, clean solvent then irrigates the coffee a second time, and a third time, etc., until all the caffeine has been removed. 

The pale yellow chloroform solution is decolorised by shaking, first with a few cubic centimetres of sodium hydroxide solution, then with the same volume of water, and is evaporated to dryness. The residue of crude caffeine is recrystallised from a little hot water. Yield 2-0-2-5 g. Soft, flexible, silky needles containing one molecule of water of crystallisation. 

Chen et al. reduced the volume of organic solvent (hexadecane) down to 1 j,L per well (usually 4—5 j,L/well) [63]. Phospholipid/hexane solution was applied on both side of the thin hexadecane membrane (40 p,g phospholipid). After the evaporation of hexane, phospholipid/hexadecane/phospholipid tri-layer was formed (according to the original article). With the 2% phospholipid/dodecane membrane (4 p,L/ well) and DS-PAMPA, permeability of some compounds such as caffeine and antipyrine were underestimated, whereas tri-layer PAMPA gave an appropriate estimate. 

Caffeine and other purine derivatives can be detected by the Murexide test. In this test the alkaloids are mixed with a tiny amount of potassium chlorate and a drop of hydrochloric acid and evaporated to dryness, and the resulting residue is exposed to ammonia vapour. Purine alkaloids produce pink colour in this test. 

Knaff and Schlunder [9] studied the evaporation of naphthalene and caffeine from a cylindrical surface (a sintered metallic rod impregnated with the solute) to high-pressure carbon dioxide flowing over an annular space around the rod. They studied the diffusion flux within the bar and in the boundary layer. The mass-transfer coefficient owing to forced convection from cylinder to the gas flowing in the annular duct was correlated, using the standard correlation due to Stephan [7]. For caffeine, it does not require a free-convection correction, as the Reynolds dependence is that expected by a transfer by forced convection. This is... 

Caffeine has been isolated from waste tea and from the decaffeiniza-tion of coffee by extraction at 70°C, using rotating countercurrent drums and an organic solvent, frequently trichloroethylene. The solvent is drained off, and the beans steamed to remove residual solvent. The extraction solvent is evaporated, and the caffeine is hot-water-extracted from the wax, decolorized with carbon, and recrystallized. 

Remove the dichloromethane by evaporation in the hood. Be careful not to overheat the solvent, since it may foam over. The solid residue which remains after the solvent is gone is the crude caffeine. Reweigh the cooled flask (3). Calculate the weight of the crude caffeine by subtraction (4) and determine the percent yield (5). 

To 50 mg of sublimed caffeine in a tared test tube add 38 mg of scilicyclic acid and 2.5 mL of dichloromethane. Heat the mixture to boiling and add petroleum ether (a poor solvent for the product) dropwise until the mixture just turns cloudy, indicating the solution is saturated. If too much petroleum ether is added then clarify it by adding a very small quantity of dichloromethane. Insulate the tube in order to allow it to cool slowly to room temperature, and then cool it in ice. The needle-like crystcils are isolated by removing the solvent while the reaction tube is in the ice bath. Evaporate the last traces of solvent under vacuum and determine the weight of the derivative and its melting point. Caffeine salicylate is reported to melt at 137°C. 

To the dichloromethane add anhydrous sodium sulfate until the drying agent no longer clumps together. Shake the mixture over a 5- or 10-min period to complete the drying process, then remove the solvent, wash the drying agent with more solvent, and evaporate the combined extracts to dryness under a stream of air to leave crude caffeine. 

Owing to the value of lupine seeds as a protein source and the toxicity of the alkaloids that may be present even in "sweet" lupine seeds, Ruiz developed a gas chromatographic method to analyse the alkaloids in such seeds. The sample (2 g seed) was finely ground and extracted with ammoniacal chloroform, and the alkaloids removed from the chloroform with a 0.1 N sulphuric acid. After basification the alkaloid bases were extracted with chloroform. The internal standard (caffeine) was added and the solvent evaporated. The residue was dissolved in ethanol and the solution obtained was gas chromatographed on a 8 % JXR packed column on Chromosorb W. The retention times of the alkaloids are listed in Table 7.5. 

Blood samples (0.1 ml) were mixed with 0.2 ml of 0.9 % Na Cl solution and 0.5 ml of glutethimide in chloroform solution. The mixture was mixed for 60 seconds and the phases separated by low-speed centrifuging. All the caffeine and glutethimide partitioned into the chloroform phase. The chloroform phase was evaporated to dryness, dissolved in 0.5 ml of acetone and gas chromatographed. The caffeine concentrations relative to the glutethimide concentrations were determined by monitoring the molecular ion of caffeine (m/e 194) to the M-28 ion of glutethimide (m/e 189). 

In order to run a series of analyses of drugs 1n pharmaceutical preparations, Fricke made use of simple extractions. Tablets containing caffeine, phenacetin and aspirin were brought into a volumetric flask, to which chloroform and a small amount of glacial acetic acid were added. After shaking for 1 h chloroform was added and an aliquot was transferred to a Celite column that was treated with 1 N NaHCO solution. After elution with chloroform, the eluate was evaporated to dryness, and the residue dissolved in methanol to about 0.3 mg/ ml of caffeine. The gas chromatography was carried out on a packed column using Dexsil 300 10 % or 17 % on Chromosorb W HP at 220°C or 222°C respectively. 

The most common use of scC02 is in the extraction of caffeine from coffee or tea, nicotine from tobacco, and essential oils from plants. The isolation of products is simple, with the evaporation of the solvent with no residue. Another important application is in supercritical fluid chromatography (SFC). 

This is the first of the coffee decaffeination patents that describe a continuous, counter-current liquid-liquid extraction. A brief description of the process is provided here. A water extract of roasted coffee beans, called coffee liquor, which contains aromas and caffeine and other water soluble components such as carbohydrate and protein materials is fed to a vacuum suipper. The extract is concentrated to about 30-50% in an evaporator-condenser and is fed to a sieve tray tower. The liquor passes across the hays in the tower downward through downspouts countercurrent to supercritical CO2 which enters the tower at the bottom and passes upward through the holes in the sieve trays. CO2 extracts caffeine from the liquor, and the decaffeinated liquor leaves the near the bottom of tower. The condensate water from the vacuum stripper prior to the tray tower is fed to the sieve trays in the top section of the tower. The water washes the caffeine from the supercritical CO2 passing upward. The caffeine-free CO2 is recycled to the bottom of the column. 

An example described in the patent relates the extraction conditions and the flow rates employed for a test The flow rates reported are huge. The patent reports that coffee liquor containing 15% solids is fed at 11,000 Ib/hr to the evaporator and concentrated to 30% solids 4,950 Ibs/hr of concentrate is fed to the extraction tower, and 5,500 Ibs/hr of condensate is sent to the top of the tower. CO2 at 40 °C and 300 atm and at a flow rate of 495,000 Ibs/hr ( ) is pumped to the bottom of the tower to strip caffeine from the coffee liquor passing downward through the tower. 

Coffee extract solution from reservoir is pumped to apacked column filled with, for example, Rashig rings, stainless steel spirals, etc. The coffee liquor flows downward over the packing and is contacted by upward flowing supercritical CO2. Caffeine is extracted from the coffee liquor which exits at the bottom of the column, and the caffeine-laden CO2 stream leaves the extraction column and enters the water wash tower (which is also a packed column) where the CO2 is stripped of its caffeine. The caffeine-free CO2 is recirculated to the coffee liquor extraction tower, and the caffeine-water solution is evaporated and the caffeine recovered. 

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. 

Ethylene glycol dimethacrylate (EDMA)-methacrylic acid (MAA) copolymer-based imprinted polymer particles were mixed with poly(vinyl chloride) in THF, and the solution was then spread on the electrode of the QCM by spin coating. After evaporation of the THF, the polymer particles were immobilized on the surface. A phenobarbital-imprinted QCM sensor prepared in this way worked in ethanol [1], while epinephrine- and caffeine-imprinted QCMs worked in buffer solutions (pH 6.0 and pH 8.0, respectively) [2, 3],... 

In the first of the three extraction methods, the natural product (coffee beans, tea leaves, or kola beans) are treated with an organic solvent that dissolves the caffeine from the plant material. The solvent is then evaporated leaving behind the pure caffeine. A second method follows essentially the same procedure, except that hot water is used as the solvent for the caffeine. A more recent procedure involves the use of supercritical carbon dioxide for the extraction process. Supercritical carbon dioxide is a form of the familiar gas that exists at high temperature and high pressure. It behaves as both a liquid and a gas. Not only is the supercritical carbon dioxide procedure an efficient method of extracting caffeine, hut it has virtually none of the harmful environmental and health problems associated with each of the other two methods of extraction. 

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