The title of this blog is pretty self-explanatory. Everyone wants to do purification quicker and slicker. Sometimes you are forced into it due to workload and other times it is an inventive idea. In this blog we will detail the benefits of using stacked injections in chiral chromatography in both SFC and HPLC modes. Most scientists are aware of the benefits of chiral chromatography in producing pure single enantiomers and it is becoming the preferred option. So the simple question is 'How do we go faster?' Shown in the top image below, is a screen shot of stacked injections using SFC. There is built in functionality within the software to help you maximise the separation. As you can see 5 injections have been completed in 24 minutes, and a total of 250 mg purified. Whereas doing single injections would take 35 minutes. This is a 31% reduction in time which will allow you to prep 5g in a working day, instead of 3.4g
Now this is all fine if you have an SFC, or the money to buy one, or the expertise to run one. However most people only have a standard HPLC prep system. Due to the longer equilibration and run times in HPLC it can have high running costs. As seen in the second image, using three variables tao (End of second eluted peak), tsp (Start of first eluted peak) and IT (Injection time) and some very clever maths you can optimise stacked injections in HPLC. It is important to note here that in can also be used for reverse phase mode if an isocratic method has been obtained. We have done this on mixtures with one critical pair, and no other impurities.
This shows we are able to prep 200mg in 20 minutes rather than 40 minutes. A time saving of 50%, or a 100% increase in amount of material, resulting in a large increase in productivity, A very useful technique to consider.
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