Environmental Laboratory 31
Automated fraction collection for faster turnaround
In fact, the effi ciency savings with the fi rst system were so good that Louise used it as an example to request the purchase of a second system. So what will the team be using their new equipment for?
Louise says: “We see the greatest value of UFPLC in cases where we have large volumes of impure material requiring hundreds or even thousands of injections. Using HPLC would generate multi-litre quantities of fractions, which would slow us down because of the backlog of samples awaiting evaporation, especially when we’re being asked to collect multiple products. But with the Shimadzu system we can automate the collection of up to fi ve fractions with no manual intervention”.
(A) The 5 litres of acetic acid washes that provided the starting material for the required acid isomers, containing just 0.3–0.4% of the target material. (B) The fi nal product as a white powder (1.5 g, 93% purity). (C) Chromatogram obtained from the mixture at the fi nal stage of method optimisation, using Shimadzu UFPLC with a 100 mm pentafl uorophenyl reversed-phase column, and a run-time of just 13 minutes. The analysis shows a sharp peak of the target compound, well-separated from a nearby ‘hump’ of unwanted material.
This, she says, makes it ideal for the initial clean-up and enrichment stage of a complex mixture. “We don’t even have to do a full separation – in a recent project on a herbicide by-product, we used a 50 mm column with a 5-minute run time, simply to remove the majority of the unwanted material and provide a small volume of a greatly enriched extract, which we could then ‘polish’ on one of our other preparative systems”.
She adds that the chromatographic reproducibility of UFPLC is critical to the ability to automate the collection of fractions – because the team are looking at products that are scarcely off the baseline, they have to rely on known retention times rather than gradient information. Another benefi t is the small fraction volumes: “In the herbicide project, the target material wasn’t particularly stable. It was therefore really useful that we were able to get it into small volumes, so that subsequent processing steps were as quick as possible”.
Reducing solvent usage
An important consequence of the team’s new equipment is not only product quality and turnaround time, but reducing the environmental impact of their methods. This is a result of being able to use short columns and short run times, with a consequent reduction in the amount of solvent they’re using.
“Reducing our solvent usage is a major benefi t of using UFPLC, and one we’re going to be looking at more”, says Louise. “On a prep HPLC method, you might be running thousands of injections on a 20 minute method at 50 mL per minute – which generates a vast amount of solvent to evaporate and ultimately dispose of. But with UFPLC, we reduce that need for solvents and the associated energy costs in evaporating them, as well as being able to use more environmentally benign solvents”.
One of the two Shimadzu UFPLC systems in the lab of the Preparative and Isolation Chemistry Team at Syngenta. The system uses trapping cartridges to collect fractions, each of which can hold ca. 100 mg of material, and can be fl ushed to change solvent, pH, remove buffers - or in the case of the acid isomers - backfl ushed with solvent to eluate the target material. The team uses a second UV detector during this backfl ushing step to minimise the eluant volume, which was kept to just 5 mL in this case.
In fact, this mission to reduce solvent usage is also a priority for Syngenta, because it makes a signifi cant contribution to the company’s sustainability goals. Supporting this, Louise’s team have a student on an industrial placement from Imperial College London, who will be using the new UFPLC systems to identify where the biggest solvent reductions can be made.
Conclusion
Author Contact Details Shimadzu UK Limited • Address: Mill Court, Featherstone Road, Milton Keynes. MK12 5RE • Tel: +44 (0)1908 552209 • Web:
www.shimadzu.co.uk
In conclusion, says Louise, with the help of the Shimadzu UFPLC they’ve been able to achieve what was previously very diffi cult – the extraction of sub-percent levels of by- products from very complex mixtures, all while keeping solvent usage down, minimising degradation of the target compounds, and reducing manual processing to the bare minimum. As she concludes, “It’s been brilliant, absolutely brilliant, and saved us so much time!”.
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