Skip to 0 minutes and 6 seconds So Joanna’s in here, and she’ll be able to help you with some more analysis. Thank you.
Skip to 0 minutes and 35 seconds Hello, Joanna. Oh, hi. We did have a look at the database and found out this was matching the MDMA - MDMA. OK. - And we need further analysis, please. All right. Excellent. Right, so we’ll prepare the sample for further analysis, and then we’ll also run a very quick experiment that’s called thin layer chromatography. Thin layer chromatography. Yeah. So let me get this vial out of the bag. So we’ve got the tablet in the vial now. So the first step is crush it up. So if I can ask you to put the tablets into here, and then crush it up.
Skip to 1 minute and 25 seconds OK. Excellent. So I’m going to go now and weigh out five milligrammes of this sample. In the meantime, if I can ask you to prepare your TLC plate. So if you could take this plate, and using a pencil and a ruler, which are over there, if you could draw two lines - one at the top, one at the bottom - and then we have three samples, so we’ll be running water, our tablet and the reference standards. So if you could just label them up, and I’ll be back in a second.
Skip to 2 minutes and 2 seconds Excellent. I can see you’re done drawing. So I’ve got five milligrammes of our tablet in this volumetric flask. So, our next step is to add our solvent, which is methanol. So if I can ask you to use this Pasteur pipette and add enough solvents so that it reaches this line over here.
Skip to 2 minutes and 25 seconds OK. I can do the final bits.
Skip to 2 minutes and 34 seconds Right. I’m going to put the lid on. I’m just going to give it a bit of a shake.
Skip to 2 minutes and 43 seconds So, I’m not sure if you can see, but if you look up closely, there are still some undissolved particles in the solution. Normally what we could do, we could sonicate it and then filter it using a syringe and a filter. We won’t sonicate it today, but we’ll filter the solution and get rid of those undissolved particles.
Skip to 3 minutes and 11 seconds So, I am now going to transfer the solution into a new vial, and I’ll ask you to then filter that solution using a syringe and a filter.
Skip to 3 minutes and 28 seconds So what you do, you have to draw up the solution, put it on the filter of the device, and if I can ask you now just to slowly press it on the syringe. OK. Like this? Yeah. Keep on going.
Skip to 3 minutes and 50 seconds So you can see that all the particles that are in soluble methanol are going to stay on the filter - Yes, I can see. - and we should get a transparent clear solution in this vial. OK. Excellent. I’ll do it once more, just to have a little bit more sample.
Skip to 4 minutes and 20 seconds So, this is now our filtered solution, which shouldn’t have any undissolved particles in it. So now, going back onto our TLC plate, we’ll have to aliquot a tiny amount of this solution, water, which is a negative control, and our reference standard, which contains MDMA, onto the plate. So to do that, you’ll use this capillary needle, and I’ll show you how to do it with our MDMA reference solution, and I’ll ask you to do it with water. So what you want to do, you want to pick up the solutions. So, now you’ve got five microlitres of that solution in your capillary needles, and then you put it on your TLC plate.
Skip to 5 minutes and 14 seconds You can gently press it down, and slowly you deposit that solution onto your plate. Use this water and aliquot it onto the plate.
Skip to 5 minutes and 37 seconds Yeah. Perfect. And I’ll just slowly press it down. Like this? Excellent. Yeah, perfect. You can give this back to me. And then the last sample we want to spot on the plate is going to be our unknown. So this is the sample we’ve just filtered. So I’m going to exactly the same thing. I’m going to pick up five microlitres of solvents, put it on the line and gently press it down.
Skip to 6 minutes and 10 seconds So now this plate needs to go into a TLC tank. So this is a tank that contains a TLC solvent. So I’ll gently put that in, and you can see that the solvent is starting to go up the plate. So the plate needs to sit in the tank until the solvent front reaches that line at the top of the plate. So that’s probably going to take six to seven minutes, so we’ll wait for it. In the meantime, while waiting for this separation to happen, we have to dilute the sample. So this is our filtered sample that we have to dilute down so that it can be analysed by another technique, which you will see later on.
Skip to 6 minutes and 58 seconds So if I can ask you to dilute this sample into this vial. So this is LCMS vial. If I can ask you to add this solvent, if you could transfer 999 microlitres into this vial.
Skip to 7 minutes and 19 seconds OK. Excellent, and now we need to add our sample. So this is a very concentrated sample, and the next technique that you will be using to analyse it is very sensitive, so that’s why we’re diluting the sample to make it less concentrated. So if I can ask you to add just 1 microlitre - so it’s going to be a tiny little drop - right into the vial.
Skip to 7 minutes and 53 seconds OK. Excellent. You can discard the tip. Thank you. So now I’ll just cap the vial and that can go on to the next step of the analysis. So the plate is now done. As you can see, the solvent front has reached that line at the top of the plate. So I’ll take it out, and I’ll just let it dry for 10 seconds, and then we’ll use the UV box to look at this plate under the UV.
Skip to 8 minutes and 27 seconds So what we can see here is that we’ve got a spot over here next to our - for our reference standard. Then, for the sample, we also have this very faint spot over here, which I will try to draw. So as you can see, they are more or less at the same level, which is indicative of our sample containing MDMA, which has shown up in our reference standard. However, this is not enough to say that the sample only contains MDMA. So now we need to take the sample that has been diluted for analysis for the confirmation.
Skip to 9 minutes and 19 seconds OK. So we’ve got our results for the TLC.
Skip to 9 minutes and 25 seconds So now we’ll take this sample to Tom for further analysis.
Separation science: thin layer chromatography
The tablet found at the crime scene will be prepared for further analysis. An initial identification of the tablet will also be carried out by a technique called thin layer chromatography.
Prepare the tablet found at the crime scene for further analysis with Researcher, Joanna Czerwinska. Carry out an initial identification of the tablet by a technique called thin layer chromatography.