Connect Someone has stolen Dr Kemp’s badminton racquet just hours before he has another important match with a year 11 student. The thief left a ransom note behind. How could Dr Kemp use chromatography to find the culprit?

So, Who is the Thief? The thief’s ink Mrs McDonald’s ink Mr Middleton’s Ink Mr Spoor’s Ink

That’s right. It was me, Mr Middleton who stole Dr Kemp’s racquet and I’d do it again! I’m just so sick of hearing how good at badminton he is!

Learning Outcomes Content Describe and compare paper and thin-layer chromatography Be able to calculate and define R f values Describe the procedure for gas chromatography Interpret gc printouts. Process Carry out thin layer chromatography on some samples and measure their R f values Benefit It is important to know the differences in the methods of chromatography so that choices can be made about which one to use.

Different types of chromatography Paper TLC GC Not used much Used a lot Cheap, quick, requires Only small amount of solvent Used a lot Expensive, quick, requires a skilled operator, very precise.

In paper chromatography what is the stationary phase and what is the mobile phase? TLC is used a lot Why? What does aqueous and non aqueous mean? What does mobile and stationary phase mean?

Thin-Layer Chromatograpy (TLC) TLC is used a lot in analytical laboratories at room temperature A plate of glass is coated with silica (silicon dioxide) or alumina (aluminium oxide) Spots are put on the plate about 1-2 cm from the end and the plate placed in a small amount of solvent. Different substances travel different distances. When the solvent has run, spots can be identified using a UV lamp or a locating agent Spots can be compared to a reference material (a known substance) to check for purity.

Analysing Chromatograms R f = Distance moved by chemical Distance moved by solvent = y/x R f = retardation factor Larger the R f the further the spot moves up the plate! R f values can be compared to known values but only for the same solvent system! X Y

Spot compounds ref A, then compounds B and C on your TLC plates. Run the TLC plates in a mobile phase of Ethyl acetate/hexane 40:60 Take the TLC plate out and mark your solvent front Allow to dry and check spot positions under UV light and mark spots with a pencil. Draw a sketch of your plate in your book and work out the R f values of your spots. Half of you….take your TLC plates to an iodine tank and place in the tank until all the spots have been visualised. The other half visualise your TLC plates with ninhydrin (I’ll spray on the ninhydrin), then heat the TLC plates Activity

Learning Outcomes Content Describe and compare paper and thin-layer chromatography Be able to calculate and define R f values Describe the procedure for gas chromatography Interpret gc printouts. Process Carry out thin layer chromatography on some samples and measure their R f values Benefit It is important to know the differences in the methods of chromatography so that choices can be made about which one to use.

How could I get a better separation between my spots if they overlay? Change my mobile phase (solvent system) Develop the TLC plate for longer Use a different UV wave length How could I see my spots better? Can you think of a way that TLC could be used in a quantitative way? Measure the intensities of the spots against a known concentration Demonstrate

Gas chromatography (GC) Very sensitive technique Good separation Quantitative Gas – mobile phase Often He (carrier gas) Sample injection port. Only a very small sample is needed. Often in liquid form The heat of the oven vaporises The sample in the column at 400 ⁰C Column in oven – stationary phase Packed with a thin film of powered solid. Some columns are 25m long and only 0.25mm in diameter. 1, The column is at temperature 2, The gas is turned on 3, The sample is injected 4, The sample passes through the column 5, The chemicals separate 6, The separation is detected by a computer 7, A chromatograph of the sample is obtained

Learning Outcomes Content Describe and compare paper and thin-layer chromatography Be able to calculate and define R f values Describe the procedure for gas chromatography Interpret gc printouts. Process Carry out thin layer chromatography on some samples and measure their R f values Benefit It is important to know the differences in the methods of chromatography so that choices can be made about which one to use.

GC chromatograph Retention time Peak intensity Separated compounds

What affect does the size of the hydrocarbon in this chromatograph have on the retention time?

Learning Outcomes Content Describe and compare paper and thin-layer chromatography Be able to calculate and define R f values Describe the procedure for gas chromatography Interpret gc printouts. Process Carry out thin layer chromatography on some samples and measure their R f values Benefit It is important to know the differences in the methods of chromatography so that choices can be made about which one to use.

Review – Complete the table PaperTLCGC Temperature Stationary Phase Mobile Phase

Review – Complete the table PaperTLCGC TemperatureRoom tempRoom Temp400 ⁰ C Stationary Phase PaperSilica or alumina Lining of column Mobile PhaseLiquid Gas (He, Ar, N 2 )