10 May / June 2014 System Requirements
UHPLC systems were designed specifi cally to be low dwell volume, in the region of 60-150µl. If you use sub 2µm particles on a traditional LC system then the effi ciency is soon compromised (Figure 6) providing only a small increase over using a normal 3µm particle.
Core-Shell however whilst also affected by system dwell volume, don’t drop as signifi cantly as UHPLC if wider bore geometries are used on traditional HPLC systems (Table 1).
Figure 5
Diphenydramine 0.02mg/ml, 0.2mg/ml, 0.5mg/ml, 1mg/ml 0.6ml/min
second is loadability/loading capacity. Generally core-shell particles have a surface area (S.A.) between 170-210m2 >300m2
wish to take this on board? Yes in theory multiple methods can be run, one for preparative scale and one for analytical scale, however this is not as productive as having one scaleable method for both departments.
In terms of loading, the smaller surface area of the core-shells can lead to a much quicker overload situation, which can compromise throughput of purifi cation, so maybe becoming a (trade off) compromise on speeding up our analysis Figure 5 (Silica matrix overload). In Figure 5 we see the loading ability of 2 silica based columns, both 50x3mm, one a traditional fully porous 3µm particle with a S.A. of 380m2
/g and one a 200m2 /g core-shell.
/g and whilst not a small surface area this is relatively low in today’s terms of /g silica’s. If your method cannot scale to preparative level then will QC and production
Conclusion
Core-Shell technology and UHPLC technology both offer high effi ciency, fast separations so is one better than the other? I am not sure that there is going to be any clear winner. Both technologies require low dispersion LC systems to provide the much vaunted effi ciencies discussed. Both technologies are not as progressed as HPLC columns, in terms of the selectivity’s available and scaleability, although on the latter UHPLC defi nitely offers an advantage if you can have the same surface area and carbon load across 1.7µm, 3µm and 5µm particles.
Figure 6
It can be seen that as we increase the mass loaded onto the columns the core-shell losses effi ciency much more rapidly than the higher surface area fully porous particle. Losses are in relation to the 0.02mg/ml sample, so by 0.5mg/ml core-shell has lost 45% effi ciency whilst the porous particle has lost only 4%. Core shell stability is still largely unproven over time as this is a ‘new’ technology and will undoubtedly be the fi rst of many iterations of the technique. Over time this should not be an issue as manufacture of these particles becomes robust, historical data will be built up to prove robustness and reproducibility.
Both these particles will fi nd use in laboratories in future. I think that personal preference will come into play, UHPLC particles are robust, but the instrumentation may be prone to blockage and is still an expert user tool. Core-shell is largely unproven and still requires low dispersion systems to work to its optimum. I think that these variables will likely split opinion in the techniques and cause people to have their personal favourite. There is no doubt that both higher effi ciency particles with much reduced run times are the future of chromatography and that they have improved the ability to speed up analysis exponentially. We need to make the most of this as manufacturers by offering a wide range of stationary phases and scaling options to aid the analysts ability to improve productivity.
The future is here and the future is faster…..
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