Chromatography of plant pigments

Discussion in 'Supporting Biology' started by Jaytee, Feb 26, 2020.

  1. Hi all, We have Edexcel syllabus here for A level. Has anyone else thought the practical seems 'dumbed down' to how we used to do it? Do you all do this version or have you changed it?
    Seems very simplistic now, ie: chromatography paper & solvent ( propanone & petroleum spirit)
    We used to do TLC plates. What's happened? I find this with so many A level practicals now, not just this one. Some of them are things we used to do at KS3 & 4.
     
  2. We do AQA and Pearson with the onus on quality.
    PLANT PIGMENTCOLLAGE.png
     
    Caroline Morgan and eddievtr like this.
  3. Julie Delaney

    Julie Delaney COMMITTEE

    that's we I did back in the good old days (1980 to be precise :(:() if it was good enough for me, it's good enough for them!.:p:p
     
    Elizabeth Gould likes this.
  4. TLC, done properly, produces a better result (see above) than paper chromatography - at a substantial price premium. I suspect the latter is all that matters to many HODs/School managers.
     
  5. Nice plates George, what mobile phase did you use?
     
  6. OMG, I am definitely having one of those weeks! I carried out TLC of Spinach & some red tree leaves . Worked brilliantly. Similar results to Georges above.
    Took it in to teacher where the A level simply filled the mortar & pestles with Spinach etc & just mashed it. Literally the things were FULL of mush. Teacher insisted they had done it properly & it was a 'rubbish' & 'didn't work' so we need to find 'better, fresher' plants. :mad:
    When I pointed out that they hadn't done it properly to release pigments she got annoyed & said they did it perfectly. Even with the evidence of mine in front of her! Maybe she thought I had coloured it in with felt tip!!
    Some days I just want to throw their practical in the bin & tell them not to bother.
    I had same with Maggot respiration yesterday. Worked perfectly in prep room. Class however, are all wandering around, messing about with equipment, screaming & shouting. Then teacher complains that it 'doesn't work'.
    It's weeks like this that get me down.:mad::(
     
    Emil Retaw likes this.
  7. Don't get yourself down Jaytee when things don't work it is the Teacher's fault either for not having a clue or not making sure that the students follow the protocol to the letter.:)
     
  8. Thanks. I think it's more that you go the extra mile, try to pre empt what they need & trial & tweek to get things working, then they just moan & simply won't accept that the kids could possibly have b******d it up!
     
  9. It's not you Jaytee When I worked in a sixth form college they did a practical which 'didn't work' so I went in and did the practical as a demo for the students where it worked perfectly as I read and followed the instructions.
     
  10. Don't worry @Jaytee I have come across the same issues time and time again - the usual reasons are nothing to do with the method, the technician or the equipment, it is nearly always one of the following:
    1. The teacher has not got control of the class so the students don't/can't follow simple instructions and/or mess about with inevitable failure.
    2. The teacher hasn't prepared the lesson properly so they don't know the procedure themselves and can't guide the students appropriately..
    3. They have not allocated enough time to instruct the students prior to the practical relying on the students to work it out for themselves, or haven't given the students enough time to complete the practical.....or both.
    4. The teacher just can't be bothered to supervise the practical properly.
    5. Of course there is always the teacher who knows better than you and follows their own method that may have worked in the distant past with different equipment or different concentrations.
    I'm sure there are other reasons as well ........but definitely not down to a technician like you.
     
  11. :) Thank you Peter. Definitely 2,3 & 4!
     
  12. We do the CLEAPSS version, works well and uses TLC plates.
     
  13. But it has its limitations in terms of resolution Amy.:);)
     
  14. We bought a pack 2-3 years ago, wincing at the price (just shy of £50 I think). However, I cut it up into small strips that just fit into sample bottles (about 1cm x 6cm), so I get around 30 runs per sheet and we're barely a tenth of the way through the box, even now. Worth the investment, for the lovely results the kids get.
     
  15. If you wrap the results in aluminium foil, they can be preserved for quite some time. Unwrapped ones will fade quickly.
     
  16. it's the chemists who seem to use it all up doing amino acids and aspirin.
     
  17. Yes many schools do it that way but unfortunately you just don't get the resolution you get when you use half a plate (as above) or tweak the mobile phase.:)
     
  18. What size plate are you referencing? We tend to use either 10x4cm or 20x4cm cut in two, depending on what is the best value at time of purchase. They are used for both plant pigment and seperation of amino acid mixtures, with references. I've had some very good luck purchasing from ebay.