A simple highly reproducible gradient system for micro column HPLC

Process monitoring by parallel column gradient elution chromatography

“…Generation of Fast Gradients. The system described is based on previous work done for micro-LC (3)(4)(5). Consider a container of fixed volume V full of solvent A.…”

“…V = 1.6 mL. Key: (1) rlbonuclease A (3 Mg): (2) cytochrome c (1 m9): (3) lysozyme (1 m9): (4) bovine serum albumin (2.5 m9); (5) /3-lactoglobulin (4 m9): (6) ovalbumin (4 µ ): (A) Sw = 0, S, = 0.5; (B) Sw = 0.2, B, = 0.5. aF = 4 mL/min, Be = 0.0, S, = 0.5. Mixer volume: 1.6 mL.…”

“…Recently, more rigorous treatments of molecular interactions in liquid chromatography have been developed that are based on a lattice-type model. These models include the solvophobic theory of Horvath and co-workers (3), the statistical thermodynamic theories of Martire and Boehm (4) and of Dill et al (5,6), and the solubility parameter theory (7)(8)(9) adapted by Tijssen and co-workers (70-72). Each of these…”

Method for Gradient Elution in Micro-Flow Liquid Chromatography

“…However, it is difficult to maintain an exact gradient profile with the preformed gradient method due to diffusion of solvent in the capillary. Yet another method is the exponential dilution method [3,4] and its variations [5,6]. With exponential dilution, a mixing chamber is first filled with a weak eluent (solvent A in this context), and the flow is then switched abruptly to a strong eluent (solvent B).…”

Variable-Gradient Generator for Micro- and Nano-HPLC

“…Split flow has been successfully used in many applications, also in combination with mass spectrometry; − however, it is not a flawless technique: first it requires flow rates higher than those commonly used, thus reducing one of the main driving forces of nano- and micro-LC; gradient distortion may occur, due to changes in column back pressure that may alter the split ratio; the mobile-phase composition variation may be delayed to the column, due to the reduced flow rate. Early attempts at the generation of low-scale gradients include a preformed gradient in which the desired slope, previously stored in a capillary, is then forwarded to the column by a syringe pump , and the exponential dilution method. − In the latter method, the flow stream is rapidly converted from the weak eluent, contained in a mixing chamber, to the strong one, leading to a concave exponential profile. This method suffers some limitations, such as a limited gradient selection and profile.…”