Experimental evaluation of chromatographic performance of capillary and microfluidic columns with linear or curved channels

- We experimentally verified the theoretical relationship between column efficiency N and peak capacity Pc.
- The relationship was utilized to estimate the column efficiency from gradient analysis.
- The method was applied to microfluidic (μLC) column efficiency testing.
- μLC columns with curved channels exhibit a bias from Pc − 1 versus N relationship.

We prepared 0.3 or 0.15 mm i.d. columns from both fused silica capillaries and planar titanium wafers with machined grooves. Both types of devices were packed with sub-two micron C18 sorbent. Chromatographic efficiency and peak capacity were tested using LC instruments with low extra column dispersion (300 nL2 or 30 nL2 for 0.3 or 0.15 mm i.d. columns, respectively). Micro column testing in gradient mode was less affected by extra column (pre-column) dispersion. To exploit this feature we developed a method for estimation of column efficiency from gradient analysis using the theoretical relationship (Pc − 1) = N0.5 × const. The validity of this relationship was experimentally verified using 2.1 mm i.d. and 0.3 mm i.d. columns.The (Pc − 1) versus N relationship was experimentally determined with straight columns, which in turn was employed for the estimation of microfluidic column efficiency. Microfluidic devices with serpentine channels exhibited lower isocratic efficiency than straight capillary columns, but the loss of peak capacity was less significant. The loss chromatographic efficiency due to zone dispersion in serpentine microfluidic channels was more apparent for 0.3 than 0.15 mm i.d. devices. Gradient performance of 0.15 × 100 mm microfluidic columns was comparable to state-of-the-art 2.1 × 100 mm columns packed with the same sorbent.