Advances in Superficially Porous Particles for Increased Method Development Flexibility and Scalability

One of the most significant recent advancements in LC column technology is the new generation of superficially porous silica particles. These particles provide similar efficiency to smaller diameter totally porous particles but with significantly lower backpressure. While chromatographers enjoy the ultra-high efficiency of these particles, they also desire more selectivity options to facilitate method development. Early introductions of SPP columns focused on expanding selectivity options with new phase chemistries, but recent innovations have enabled the use of pH as a selectivity tool through new approaches to particle development. Additionally, expansion outside the small molecule arena into biopharmaceutical applications with multiple particle and pore size options is further fuelling growth in usage of these Fast LC columns.

Over the past few years, superficially porous particle (SPP) columns have seen tremendous growth as users have recognised their advantages over traditional totally porous columns. For new methods, the popularity of SPP columns has exceeded that of sub-2 μm columns. Major benefits include robustness, high efficiency, and low backpressure. Modern superficially porous particle columns were introduced in 2006, when Kirkland and co-workers commercialised the first sub-3 μm SPP column (DeStefano, Langlois, & Kirkland, 2008). Since that time, multiple manufacturers have introduced their own families of SPP columns, including AMT HALO, Phenomenex Kinetex, Agilent Technologies Poroshell 120, and Waters CORTECS, a recent introduction to the SPP market. Additionally, many smaller companies have started to offer their own SPP columns as well, leading to wide adoption of these technologies in the HPLC chromatographic laboratory.

These columns have been shown to improve separation efficiency significantly (Long & Wang, 2012), enabling the ability to utilise faster methods to achieve higher throughput. With more and more laboratories focusing on increasing sample throughput, migrating to these SPP technologies can provide significant advantages over totally porous columns. Furthermore, adopting larger particle size SPP columns versus sub-2 μm columns translates to lower backpressures, enabling chromatographers to get the most out of their LC systems.

While migrating to SPP columns provides significant advantages over totally porous columns, there have been some challenges associated when the technology was initially launched. Method development, for example, typically takes advantage of multiple chemistries to exploit various aspects of analyte interactions for achieving desired resolutions. Early in the release of this column technology, chemistry choices were limited, reducing the options for method development. However, as the column families expanded, so have the number of chemistries, increasing the flexibility for chromatographers. Additionally, recent improvements to the particles themselves enable robust operation under high pH conditions (Use of Agilent Poroshell HPH-C18 Columns at Elevated pH as a Tool for Method Development, 2014), enabling the utilisation of pH as a method development tool without the fear of reduced column lifetime under elevated pH conditions.