|Matching 1st and 2nd dimension chemistries in the 2D-LC. Active Solvent Modulation
|Fundamentals in Separation Science (KVCV)
Abstract Information :
Two-dimensional liquid chromatography (2D-LC) is often used to solve difficult separation problems ranging from targeted analyses of structurally similar molecules to untargeted separations of highly complex samples. In a 2D-LC system, aliquots of effluent from the first dimension column (1D) are transferred to the second dimension column (2D) with the goal to separate the compounds that might have co-eluted in 1D.
One of the well-known challenges in the 2D-LC is matching the elution strength of the 1st dimension effluent to the separation method in the 2nd dimension. In many cases (RP xRP; HILIC x RP; pH-mismatch) the 1D sample matrix (solvent in which compound was sampled for injection into the 2nd dimension) may be too strong for sufficient retention on the 2D column. This can lead to severe peak distortion and a loss of resolution and sensitivity, especially if the aliquot volumes transferred to 2D are significant.
It is thus desirable to adjust the aliquoted solvent prior to injecting it onto the 2nd-D column in order to avoid elution artifacts. In the case of on-line conjugation of the 1st and 2nd dimension, i.e. when the aliquots are provisionally stored in loops (rather than in vails), such solvent adjustment can be challenging.
This presentation shows the concept of Active Solvent Modulation (ASM). This novel valve-based approach not requiring additional hardware enables sample dilution by a pre-configured dilution factor prior to application of the sample to the 2nd-D column.
The effect of ASM on the gradient shapes arriving on the column in the 2ndD and baseline shapes in sensitive applications, like those using TFA or FA as eluent additive is discussed. Improvement of the separation performance in the 2nd dimension by applying ASM is demonstrated on a case study.