Chem143 Lab 9 Martin Case Corinne Sadlowski Extraction of Limonene using Liquid CO2 http en wikipedia org wiki Carbon dioxide http en wikipedia org wiki Limonene Write up for this lab to be completed on 11 17 and 11 19 Reagents and Equipment Finely grated orange peel 2 5 g Solid carbon dioxide dry ice 5 g Centrifuge tube Copper wire Filter paper Disposable pipettes GC MS vial Purpose Extraction of natural products from plant animal bacterial and fungal sources is an important part of organic chemistry Many pharmacologically important molecules have been isolated from natural sources Some important examples are penicillin an antibiotic aspirin an analgesic and taxol an aniticancer drug Traditionally these natural products have been extracted by leaching with water or an organic solvent in the same way that flavors and caffeine are leached from tea by boiling water Needless to say these organic solvents are usually hazardous and elevated temperatures are usually required for effective extraction In this lab you will investigate the usefulness of supercritical carbon dioxide as a green solvent You will measure its efficiency in extracting an essential oil from a biological source and you will determine the identity and purity of your product using GC MS Introduction Essential oils are organic compounds that are extracted from natural sources and used in many products such as flavorings fragrances and cleaning products The predominant essential oil in the rind of oranges lemons and limes is limonene Limonene is biosynthesized as a single optically active enantiomer D limonene Figure 1 CO2 is useful as a green solvent because it provides environmental and safety advantages it is nonflammable relatively nontoxic readily available and environmentally benign Large scale CO2 processing is used commercially for the extraction of various food products including essential oils and hops and for the decaffeination of coffee and tea CO2 is useful for these processes because unlike most other gases it has an easily accessible liquid phase As shown on the phase diagram in Figure 2 CO2 sublimes goes directly from a solid to a gas at 1 atm The triple point of CO2 where solid liquid and gas phases 1 Figure 1 D Limonene Chem143 Lab 9 coexist in equilibrium is achieved at 5 2 atm and 56 6 C At or near this point liquid carbon dioxide forms If the temperature and pressure are increased to the critical point 73 8 atm and 31 0 C the CO2 exists as a supercritical fluid and has no distinct liquid or vapor phase but properties that are similar to both If the CO2 is sealed in a vessel during sublimation the internal pressure in the vessel increases At sufficiently high pressure liquid carbon dioxide forms We will use liquid CO2 to extract limonene from orange peel The CO2 solvent is easily removed by returning the extraction vessel to atmospheric pressure by removing the cap and allowing the CO2 to boil away Martin Case Corinne Sadlowski Figure 2 Pressure temperature phase diagram for CO2 Procedure Figure 3 Procedure for liquid CO2 extraction of limonene A support is constructed by bending copper wire into coils and a handle and placing a filter paper between the wire coils The support is placed in a centrifuge tube and finely grated orange peel is placed in the tube Dry ice is added and the tube is sealed with a cap The sealed tube is placed in warm water in a plastic cylinder 1 Grate only the colored part of the peel of 1 2 of a medium sized orange with the smallest grating surface of a standard cheese grater or zester into a pre weighed weighing boat Make sure you have at least 2 5 g of grated orange rind 2 Weigh a 15 mL centrifuge tube and record the mass Using a 20 cm piece of copper wire and a piece of 1 5 cm filter paper or circle of small mesh metal screen make a support for the peel and dry ice Slide a piece of filter paper between the coils making a base to support the solid and fold up the edges around the wire Slide the support into tube Add approximately 2 5 grams of grated orange rind Record the exact mass of orange peel 2 Chem143 Lab 9 Martin Case Corinne Sadlowski added to the tube 3 Fill a plastic cylinder or large mouth polycarbonate water bottle one half to two thirds full of warm 40 50 C tap water 4 Fill the rest of the centrifuge tube with crushed dry ice Tap the tip of tube on the bench to settle the contents and add more dry ice until the tube is full Twist cap on tightly until it stops turning 5 Immediately after capping drop centrifuge tube into the water in the cylinder Pressure will begin to build in the tube and gas will escape slowly from the region where the tube and the cap meet The plastic cylinder functions as a secondary container and protects you from possible injury Watch the extraction from the side not the top of the cylinder 6 After about 15 seconds liquid CO2 should appear If no liquid has appeared after 1 minute there is not a sufficient seal Remove tube from cylinder tighten cap and put back in water If repeated trials do not produce liquid the cap or tube may need to be replaced Liquid should boil and gas should escape for 2 3 minutes While the extraction is proceeding slowly rotate the cylinder on its base to prevent the centrifuge tube from freezing to the side of the cylinder Never remove the tube from the plastic cylinder when the CO2 is liquid As the liquid boils it should pass through the peel and move to the bottom of the tube 7 After the liquid has evaporated and gas is no longer escaping remove the tube from the cylinder with tweezers and carefully open the cap Open centrifuge tubes slowly and only after the gas has escaped 8 Perform a second extraction If necessary a piece of wire can be used to break up the solid mass and create a channel to the bottom for liquid CO2 Refill the tube with dry ice reseal the cap and put the tube back in the water A third extraction can be performed in the same manner if desired The orange peel does not need to thaw between extractions 9 After three extractions the product approximately 0 1 mL pale yellow oil should be in the tip of the tube Carefully remove the solid and the trap by pulling the wire handle with tweezers If any solid remains in the tube remove it with a spatula or wire 10 Dry the outside of the tube and determine the mass of the product Calculate percentage recovery based upon the yield of the product compared to the mass of rind used Write up Calculate and comment on your yield Based on the GC MS comment