OHS026 1. Completed by: Dr. Pall Thordarson and A/Prof. Jonathan Morris Safe work procedure Staff/Student number: The Writing Safe Work Procedures Guideline (OHS027) should be consulted to assist in the completion of this form Faculty/Division: Faculty of Science Document number F10-SWP-303 School/Unit: School of Chemistry Initial Issue date: 16-August 2011 Current version: V1.1 Current Version Issue date: 31-August 2011 Next review date: 31-August 2013 2.Safe work procedure title and basic description of activity Title: Column Chromatography using gravity (unpressurised) Description of activity: Proper usage of column chromatography under gravity (silica or alumina) 3.List Hazards and risk controls as per risk assessment Associated risk assessment number and location: F10-RA-303 See School of Chemistry Safety Page and Faculty of Science Database Hazards: Silica or alumina dust Controls Proper training, consult MSDS for silica or alumina. The silica used for chromatography is a very fine dust that is will damage the lungs. Alumina dust is also toxic and harmful to the respiratory system. Ensure all work with silica or alumina is carried out in a fume hood. Use facemask (type: AS 1716 P1) for larger quantities (> 50 g). Physical injury due to glassware Appropriate training: Inspect columns, sample and collection vials for cracks before use and replace if faulty. . Spillage and contamination from chemicals used to run the flash column, Fire and explosion Consult MSDS for all chemicals used and fill in the corresponding School of Chemistry Risk assessment form. Appropriate training. First aid on site. Wear proper PPE, especially chemically compatible gloves and protective eyewear. Dilute corrosive substances if possible. Avoid ignition sources. Carry all work out in a fume hood. Clean up spillages immediately. 4.List resources required including personal protective clothing, chemicals and equipment needed Materials and Equipment • Glass column for chromatography (solvent reservoir optional). • Chromatography grade silica or alumina. Acid-washed sand (optional) • Solvents to run column with (hexane, ethyl acetate, dichloromethane and methanol the most common ones) • The sample to run. Pipettes if required for transferring sample. • Funnel(s), cotton to plug the column if necessary, aluminum foil (to cover column if material is light sensitive) • Collection vials for the eluent / products from column. Personal Protective Clothing and Equipment • Protective safety glasses • Laboratory coat • Gloves (choose according to chemical compatibility and/or physical hazard) • Facemask (if required), minimum AS 1716 P1 type. _______________________________________________________________________________________________________________ Page 1 of 5 OHS026 safe work procedure Current Version: 3.0, 04/03/2011 5.List step by step instructions or order for undertaking the task NOTE: If you indent to use pressurised gas, please don’t use this SWP but consult the SWP for flash column chromatography. Preparing and packing the column This procedure MUST be done in a fume hood! Use of facemask is recommended for larger quantities (> 50 g). • Only suitably trained persons can do column chromatography. • Choose the appropriate column size for your separation. Consult your supervisor if unsure. W. Clark Still, M. Kahn and A. Mitra (J. Org. Chem., 1978, 43, 2923) also provide some advice on this for the related technique of flash (pressured) column chromatography. Longer columns are not necessary better – this needs to be balanced with how well you can control the flow rate to be at optimum (Van Deemter plot – see e.g., http://www.reachdevices.com/SetUpColumn.html) with 20 cm more than sufficient in many cases. Focus rather on the appropriate diameter for your column to give the optimum sample-to-silica (or alumina) ratio. • Some columns come with a pre-fabricated frit at the bottom. These make loading easier but not favoured by all as this may increase the dead volume. If your column is not fitted with a frit, you need to plug the bottom. Make a cotton plug and insert at the bottom of the column with the tap closed. To push the plug in you may have to use a designated metal or glass rod – take extra care not to break the column doing this and if using a glass rod, don’t apply too much pressure or touch the end of the rod. Don’t use excessive force to push the plug in. Good hand protection (e.g., leather gloves) is strongly recommended. • Clamp the column in position. If desired, you may want to add a layer of sand on top the cotton plug or frit. Add a little bit of your first eluting solvent if desired to wet the plug / sand. • To pack the column there are essentially two different procedures; i) slurry packing and ii) dry packing. The choice between these will depend on the circumstances of your separation problem and personal preference. Consult supervisor if unsure. i) Dry packing: Measure out the required amount of silica or alumina from its container in a fume hood into a beaker or similar vial. Add solvent to the column to a level little above the desired length of your packed column. Using a dry funnel, sprinkle the silica or alumina into the solvent. Tap the column gently with a pencil to help the silica or alumina to pack and allow solvent to drain from the column into a conical flask to prevent overflowing.* Let the silica or alumina settle and drain the solvent under gravity until the solvent level is just even with the surface of the silica or alumina.** ii) Slurry packing: Measure out the required amount of silica or alumina from its container in a fume hood into a conical flask or a similar vial. Add your solvent (typically 2-3 mL per gram for alumina but up to 10 mL per gram for silica) of the to the silica or alumina and swirl around gently until a uniform slurry is obtained with no visible dry pockets or air-bubbles. Add more solvent if necessary. Note when using alumina that this procedure can be quite exothermic. Fill your column with solvent to a level above the desired packed column length. Using a funnel, quickly pour the slurry into the column. Place an conical flask under the column, open the tap and allow the liquid to drain into it but don’t let it drain below the level of your silica or alumina.* Continue to transfer the slurry to the column until all the silica or alumina is added. Add more solvent if necessary. When finished packing, drain the excess solvent under gravity until the solvent level just reaches the top level of the silica or alumina.*/** Close the tap. Your column is now "packed”. *In many circumstances you can reuse this solvent – consult your supervisor for advice is this the appropriate course of action for your system. **If desired, you may want to add a layer of sand on top of the silica to make it’s surface sturdier (n.b., this may though decrease your separation power). If you are planning to do this, don’t train the solvent completely, leave ca 3-6 cm layer of solvent, sprinkle the dry sand gently via funnel into the column. Once the sand has settled, drain the excess solvent under gravity until the solvent level just reaches the top level of the silica (it is OK if the sand is partly dry). • • If you are working with light-sensitive materials, cover the outside of the glass column with aluminum foil up to the top level of the silica or alumina. Unless you stay with the column at all times, you also need to identify the content of the column (solvent, sample, silica or alumina) by attaching a label directly on or near the column. Loading the sample • This procedure MUST be carried out in a fume hood! • Only suitably trained persons can do column chromatography. • To load the sample there are essentially two different procedures; i) wet loading and ii) dry loading. The choice between these will depend on the circumstances of your separation problem and personal preference. Wet loading is _______________________________________________________________________________________________________________ Page 2 of 5 OHS026 safe work procedure Current Version: 3.0, 04/03/2011 ideal when your sample is freely soluble in the solvent you use to start the column with while dry loading is preferable if the sample is not soluble in the solvent you start with. Consult supervisor if unsure. i) Wet loading: Test if you sample is soluble in the solvent you use to pack the column with and you indent to start the column with. N.b., using a different solvent to dissolve your sample than used to pack/elute the column with can severely affect your separation. Dissolve the sample you have with minimum amount of solvent (generally < 5 mL). Carefully use a Pasteur pipette or a syringe with a wide needle to transfer the solution to the column. Addition must be carried out in such a manner that the silica surface is not disturbed (even when a protective layer of sand is used). Use 1-2 mL of solvent to rinse your sample vial and transfer this solution also to the column in the same manner. ii) Dry packing: In a suitable large round-bottom flask, dissolve your sample in a suitable solvent (this does not have to be the same solvent as you use for elution on the column) and add to this solution about 1/20 to 1/10 of amount of dry silica (dry packing is rarely used with alumina columns) you used to pack the column. Add more solvent if necessary until you form a uniform slurry. This slurry is then gently evaporated on a rotary evaporator which leaves a dry batch of silica saturated with the sample to be separated. It should be a free flowing powder. If it is still an oil, add more silica and repeat the procedure. After this mix is prepared, additional eluant is poured into the silica column to get about one inch of eluant above the silica. The powder is then added, making sure to always retain a small (1.5-3 mm) eluant layer (if all the eluant getting absorbed by this addition more eluant must be added). The goal is to form bubble-free slurry over column packing without much disturbance. This does require practice. • Whether you use the wet or dry loading method, the last step is to lower the solvent under gravity again down to just above (1.5-3 mm) the level of silica or alumina. Fresh eluant is added then so that its level reaches about 10 mm and this is drained again to just above the silica or alumina level (1.5-3 mm). This step is repeated one or two more times. The column is now ready for eluting which should be done immediately to avoid accidental solvent draining below the top silica layer due to leaks or evaporation of the solvent. Running the column and finishing up • This procedure MUST be carried out in a fume hood! • Only suitably trained persons can do column chromatography. • Add as much as you desire of your eluant gently (or as much as fits). Start eluting the column. The flow rate is adjusted by the column's stopcock. • Collect your fractions in the appropriate vials. Keep these if possible in the fume hood while determining which fraction you wish to isolate/combine and then transfer to round bottom flask(s) for removing the solvent (if desired). If you need to keep the vials for prolonged periods, cover with aluminum foil and leave in a fume hood. • When you have completed your run it is good practice to drain all the solvent of the column under gravity. • To empty the silica or alumina from the column the use of a facemask 1716 P1 type is highly recommended and ALWAYS REQUIRED FOR LARGER QUANTITES (> 50 g). Start this procedure by placing the column upside down above a large beaker (several times the volume of the silica used) AS FAR AS POSSIBLE AT THE BACK OF A FUME HOOD with the sash down to minimize exposure to the silica or alumina dust. If the silica or alumina is already dry it may fall out quickly under gravity. Otherwise leave it either to dry and fall out over a period of time (e.g., overnight) or put a nitrogen hose on the stopcock end of the column and apply VERY GENTLE pressure to push the silica or alumina down out of the column. 6.List emergency shutdown procedures Mop up spilt silica or alumina with damp cloth. If silica or alumina is inhaled move to fresh air and obtain medical assistance. In case of solvent spillage, do not operate switches nearby and mop up solvent if in fume cupboard. If spillage occurs outside fume hood, evacuate area and allow to evaporate. Turn off nearby power at power point. If unable or unsafe to do so use the emergency cutoff switch (red button) for the laboratory (e.g., lF10-234) usually located on the wall near the entrance to the lab. 7.List Emergency procedures for how to deal with fires, spills or exposure to hazardous substances Contain the fire or spillage if safety of all personnel is not compromised, otherwise shutdown the power using the emergency cutoff switch (red button) for the laboratory (e.g.,, lF10-234) and call the security for emergency (x56666). 8.List Clean up and waste disposal requirements • Disposal of used silica or alumina should be into an appropriately labelled solid-waste container. • Consult MSDS and place any solvents or chemicals used in the appropriate waste containers; non-halogenated solvents/chemicals in non-halogenated waste and halogenated solvents/chemicals in halogenated waste. 9.List legislation used in the development of this SWP _______________________________________________________________________________________________________________ Page 3 of 5 OHS026 safe work procedure Current Version: 3.0, 04/03/2011 NSW OHS Act 2000, NSW OHS Regulation 2001, Code of Practice for the Labelling of Workplace Substances AS/NZS 2243.2:2006. Safety in laboratories. Part 2: Chemical aspects AS/NZS 2243.6-1990. Safety in laboratories. Part 6: Mechanical Aspects. AS/NZS 2161.1:2000 Occupational Protective Gloves – Selection, Use and Maintenance 10a.List competency required – qualifications, certificates, licensing, training - e.g. course or instruction: All personnel operating this equipment must have training and instructions on the safe use of the equipment and they must be assessed as competent. 10b. List competency of Assessor Academic supervisor, post-doctoral fellow or senior PhD student (minimum 1 year into PhD). 11.Supervisory approval, And review Note: Local supervisor must determine appropriate authorisation and final sign off when this document is downloaded. Supervisor: Signature: Responsibility for SWP review: Date of review: 12.SWP Sign off sheet SWP name and version: In signing this section the assessor/ authoriser agrees that the following persons are competent in following this SWP Name Signature Date Competent Name of Assessor/Authoriser Assessor/Authoriser signature _______________________________________________________________________________________________________________ Page 4 of 5 OHS026 safe work procedure Current Version: 3.0, 04/03/2011 _______________________________________________________________________________________________________________ Page 5 of 5 OHS026 safe work procedure Current Version: 3.0, 04/03/2011