Field flow fractionation (FFF) has existed for more than 40 years and is primarily used for the separation and characterization of large particles; however, it has not reached the popularity of other separation techniques for this application. FFF works much like LC, but uses a thin flow channel instead of a column. In place of the stationary phase, an externally generated field is applied perpendicularly as a sample is washed down the channel, separating the sample’s components. The main advantages are that it works well with large complex molecules and that it is gentle. Although the uses of FFF are many, only a handful of companies provide systems. One of these companies is PostNova Analytics. Founded in 1997 and based in Germany, the company acquired the intellectual property of FFFractions, founded by FFF’s inventor J. Calvin Giddings, in 2001.

Trevor Havard, vice president of Sales at PostNova Analytics, told IBO that early FFF systems designed for symmetrical flow (see IBO 7/15/02) were too complex, not developed for a mass market and did not target popular applications. Postnova hastened development of the FFF market, introducing streamlined and user-friendly technology, such as Asymmetric Flow FFF (AF4) (see IBO 8/31/08). In AF4, the external field is generated by an additional cross flow within the channel. “AF4 has revolutionized [FFF] with well-engineered systems and improved software control of the systems,” said Mr. Havard. PostNova differentiates its FFF systems by eliminating the need to switch valves and flow controllers. According to Mr. Havard, this improves reproducibility, recovery and system maintenance.

This year, PostNova introduced the TF 2000 Thermal FFF (ThFFF) system. According to Mr. Havard, PostNova is the only company that has commercialized a ThFFF system, which is used for polymer analysis. In ThFFF, instead of an external force, a temperature gradient is used for fractionation. Advantages include fractionation based on chemical composition and higher selectivity for large polymers.

ThFFF can also be combined with multi-angle light scattering (MALS) detectors for absolute molecular weight or size characterization. PostNova introduced the TF2000-MALS last year, applications for which include the characterization of high molar mass molecules and microgels. “The applications of this technology in process monitoring are in an early stage, but have massive potential,” said Mr. Havard. Other systems that only PostNova offers include the S101 series of sedimentation FFF systems (where the external force is generated by spinning the channel) for measuring dense nanoparticles, and a high-temperature AF4 system for use in the polyolefin market.

It takes more than accessible instrumentation and new products to grow a market; it also takes new applications. According to Mr. Havard, the focus on large molecule characterization in the biotech, environmental and polymer markets is helping FFF demand. “In the biopharmaceutical market, the applications range from aggregation determination, [to separation of] bacteria, virus and vaccines and liposomes. All these large molecules and clusters are often impossible to separate by HPLC,” he explained. In contrast, AF4 separates cells and proteins while preserving their activity.