Hi, you already know what a chromatogram is. This is part of a chromatogram and with fractionation

your goal is to collect or to fractionate as much of one component of a mixture of substances

as much as possible and also to guarantee a certain purity. So your end product should

be at least, for example, 90% of a certain component of your mixture since then you can

make sure that your end product has the properties you want and you can work with it. So assume

our chromatogram here and we want to fractionate the middle peak and we need to guarantee 95%

of purity. In that case we can decide where we want to fractionate and mark those times

with these collectors. For example here, make this green and here. Of course the other peaks

or the other substances overlap in our fractionation time. So here's a little bit of overlapping

and here but since we have a purity of 95% this is okay and the exact solution is not

possible here right now since in that case we would need a computer. So we have optimal

fractionation times for this chromatogram. However, during a chromatography process there

can be the temperature in the laboratory is too hot or some parameters are not set exactly.

So the chromatogram is not this but this and in that case you can see that here there's

a lot of overlapping and also here it is a huge amount of overlapping. So in that case

our purity does no longer hold. For that chromatogram the optimal fractionation times would be here,

let's make it blue and maybe here. So since there is a lot of overlapping on that side

the fractionation times need to be more narrow here. Alright or something is different in

the process and the chromatogram looks like that. In that case you can see that here is

the purity not guaranteed so the overlapping on that side is too much. So we need to stop

the fractionation maybe here. And on the other side here there are, they cut the component

very much so for that chromatogram we can start the fractionation already here. Otherwise

we lose too much of the component. So if you assume that you need to determine when to

start the fractionation and when to end it and you don't know what chromatogram you will

get. So you can get one of those three chromatograms. You can't optimize the fractionation time

for each chromatogram since in that case you have a 33% chance that your end product will

meet the constraints and a 66% chance that it will not. In that case you need to determine

the robust solution. A robust solution gives you in that case the fractionation times so

that the purity is guaranteed no matter which of the three chromatograms you will get in

the end. And for that you need the interval of fractionation times that is inside the

fractionation for each chromatogram. So the latest fractionation start and the earliest

fractionation end. That would be here. So for this chromatogram you are on that side

your purity is met and on this side your purity of course is met too but you lose a little

bit of product so the solution could be better. That's the so called price of robustness.

In order to get the protection and in order to be you can be sure that your end product

fulfills your purity the productivity might be a little bit less. So it is not the optimal

solution but it is a good solution that is feasible for all problems. And if we look

at the next chromatogram here also here you meet your purity and in that case you also

meet your purity but cut a lot of your peak. Of course it is possible that the robust solution

is too conservative. This means that in some cases you lose too much mass and your process

your solution is not productive enough. In that case you have to go back to your processes

and measure your parameters more exactly or you have to control your settings more so

your possible chromatograms are not that different. This means that the possible outcomes are

not so different than before and in that case your robust solution will become better. And

of course for the last chromatogram you are inside your purity so here and here the purity

is guaranteed and in this case you lose only a little bit of mass. Alright now to your

challenge. Now it is your turn to try this on your own and for that we have here three

chromatograms. You have to try to fractionate this peak that is marked with the arrow and

for that you can pull your chromatogram in this field. You have to make sure that it

is exactly inside the orange lines so your axes are not exactly overlapping. Then you