Implementation of high slurry concentration and sonication to pack high-efficiency, meter-long capillary ultrahigh pressure liquid chromatography columns

Abstract

Slurry packing capillary columns for ultrahigh pressure liquid chromatography is complicated by many interdependent experimental variables. Previous results have suggested that combination of high slurry concentration and sonication during packing would create homogeneous bed microstructures and yield highly efficient capillary columns. Herein, the effect of sonication while packing very high slurry concentrations is presented. A series of six, 1 m × 75 μm internal diameter columns were packed with 200 mg/mL slurries of 2.02 μm bridged-ethyl hybrid silica particles. Three of the columns underwent sonication during packing and yielded highly efficient separations with reduced plate heights as low as 1.05.

FlashPack: Fast and simple preparation of ultra-high performance capillary columns for LC-MS

“…S7). The FWHM standard deviation between the five tested columns was 8.67%, which was comparable to that reported for ultra-high pressure packing protocols [25].…”

Bed morphological features associated with an optimal slurry concentration for reproducible preparation of efficient capillary ultrahigh pressure liquid chromatography columns

“…In fact, our preliminary efforts in column packing using these insights allowed the combination of very high slurry concentration and ultrasound during column packing to prepare extremely efficient one-meter long capillary columns. These columns boast with a plate count of~500,000 over one meter of packed bed and a reduced plate height near unity [38]. Following this avenue can lead us to the realization of great improvements in one-dimensional separations of very complex samples.…”

“…Particle slurries were prepared by mixing a known mass of the particles in a known volume of acetone. Acetone was chosen because C18-modified BEH particles slurry well in this solvent and to mirror previous studies for comparison [2, 13, 38]. The following slurry concentrations were used: 5, 20, 40, 60, 80, 100, 120, 140, 160, 180, and 200 mg/mL.…”

“…The results are used to shape our knowledge of the packing process, to confirm general trends on the optimal slurry concentration in dependence of the packing protocol, and to suggest possibilities for optimization of the packing process towards higher separation efficiencies. In fact, the insights gained from this detailed study in combination with our previous work already allowed us to improve the packing procedure and create extremely efficient capillary columns [38]. …”

In-column bonded phase polymerization for improved packing uniformity

“…The introduction of sonication during slurry-packing for submicrometer particles provides high radial uniformity in capillaries by promoting rapid transverse transport of particles during packing, shown by an eddy diffusion term of less than 10 nm [18]. Extremely long LC columns, 1 m in length, have shown improved eddy diffusion using sonication during slurry packing of 2 μm particles, giving reduced plate heights on the order of unity and plate number in excess of 50 0000 [19]. The challenge of F I G U R E 1 Depiction of the structural distinction between columns packed with particles that (A) had polymer grown before packing (ex situ) versus (B) particles containing initiator but no polymer, with the polymer subsequently grown on the particle surface inside the column (in situ) uniform packing remains unmet for particles with polymer bonded phases.…”