We all know that HPLC and SFC both have their place in chiral and now achiral purification. We all know that SFC, when appropriate can be quicker, cheaper and more efficient. However some examples can show this at its extreme.
A four component sample arrived in the lab. A customer had already performed method development on the immobilised CSP and found a separation. One drawback . . .100 minutes! Not a quick prep, also poor loading due to solubility so DCM had to be used. Alongside the cost of heptane which at 21mL / min works out to be very expensive.
Onto the SFC screen it went and several runs in we found it, an SFC method with partial separation of all four isomers. A couple of minutes later and a 40% isocratic method and complete separation achieved.
Then came the super bit, due to the use of methanol as the eluent, solubility was no longer an issue which meant much higher loadings. On an HPLC it was 25 x 20mg injections. On SFC 10 x 50mg injection.
Cost of each injection
HPLC – 21mL / min of a heptane / ethanol mix over 100 minutes = £40 per injection
SFC – 60mL / min of 40% methanol over 6 minutes = £3 per injection
This was a huge solvent cost saving of over 90% per injection, and a time saving of over 90% per injection. It doesn't always work this was but when it does SFC is a very powerful tool, and it highlights the need for both techniques in a purification laboratory.
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