Improving peak shapes with counter gradients in two-dimensional high performance liquid chromatography

Assessing the detectability of antioxidants in two‐dimensional high‐performance liquid chromatography

“…To overcome this serious issue, a countergradient was employed to alter the solvent composition of the transferred eluent to a concentration that was close to the initial composition of the second dimension . This resulted in a more efficient separation with peaks conforming to the Gaussian profile.…”

“…The conditions for the countergradients were calculated according to Stevenson et al . , which were programmed into Mathematica 9 (distributed by Hearn Scientific, South Yarra, Victoria, Australia). As the introduction of the countergradient added a significant volume to the fraction and therefore diluted the sample, the second dimension injection volume was increased to 100 μL.…”

“…Stevenson et al . overcame solvent strength mismatch in 2D‐HPLC by incorporating a countergradient into the experimental design. Mixing two different programmed gradients allowed for precise control over the injection plug entering into the second dimension.…”

Effects of pH mismatch between the two dimensions of reversed-phase × reversed-phase two-dimensional separations on second dimension separation quality for ionogenic compounds—I. Carboxylic acids

“…In this case, where the pH was low in both RP separations, we demonstrated that detection sensitivity following the 2 D separation could be improved considerably by first diluting the 1 D effluent with water (weak solvent in the RP mode), and then injecting the entirety of this diluted effluent, in spite of the fact that the volume of the resulting injected fraction is much larger than it is if no dilution is used at all. This is certainly not a new concept [14][15][16][17], and there are alternative approaches to promote focusing of the analyte band at the inlet of the 2 D column, each with its own unique strengths and weaknesses [18][19][20][21][22][23]. Nevertheless, in our hands the dilution approach has been a very effective strategy that is easy to implement in practice.…”

Application of fractionized sampling and stacking for construction of an interface for online heart-cutting two-dimensional liquid chromatography

“…For HILIC × RP 2D LC, dilution of 1 D eluate prior to injection into 2 D column has achieved lots of good performances [18][19][20][21][22]. Typically for those techniques using additional dilution pumps and trap columns, dilution and trapping of 1 D eluate occurred at the same time and thus usually need high pressure pump to provide high-flow-rate weak solvent.…”