The automated backpressure regulator (ABPR) is a weak point in any SFC system. Like pump seals and check valves, any disruption of smooth operation can not only change flow or pressure but can dramatically affect chromatography. In bulk preparative SFC, any change in chromatography can destroy an automated stacked injection run, so a stable backpressure regulator is critical.

Our ABPRs use the Thar needle and seat design. The device adjusts the fit of the needle in the compressible seat, repeatedly closing and opening slightly as it attempts to maintain pressure. As the device wears, it adjusts the needle pressure too frequently, resulting in an unacceptable pressure fluctuation. Lowering the pressure setting requested stabilizes the fluctuation, implying that the wearing of the needle/seat is worse at higher settings. Taking the load off the ABPR might improve lifetime and performance.

We tested this hypothesis using a fixed backpressure cartridge (Upchurch P/N U-469 [holder] and P-796 [1000 psi cartridge]).