1. Feed injection in liquid chromatography: Reducing the effect of large-volume injections from purely organic diluents in reversed-phase liquid chromatography.
- Author
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Böth, André, Foshag, Daniel, Schulz, Charlotte, Atwi, Boshra, Maier, Sarah E., Estes, Deven P., Buchmeiser, Michael R., de Goor, Tom van, and Tallarek, Ulrich
- Subjects
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LIQUID chromatography , *SUPERCRITICAL fluid chromatography , *STREAMFLOW , *RF values (Chromatography) , *DILUTION - Abstract
• Classic and feed injection modes applied to microreactor–offline RPLC analysis. • Solvent effect on band broadening investigated with large-volume injections. • Influence of diluent, injection volume, feed rate, flow rate, and retention studied. • Range of optimal ratios between mobile phase flow and feed rates identified. • Range depends on retention factor – independent of injection volume and flow rate. In liquid chromatography (LC), discrepancies in liquid properties such as elution strength and viscosity lead to a mismatch between the sample diluent and mobile phase. This mismatch can result in peak deformation, including peak splitting or even breakthrough, particularly when large sample volumes are injected. The formation of a T-junction between sample solution and mobile phase flow stream, a technique previously used in supercritical fluid chromatography, is the key enabler of feed injection in LC. This T-junction allows the injection needle to infuse the sample directly into the mobile phase. It ensures that the diluent is continuously mixed with the mobile phase before introduced onto the column, thereby reducing the initial solvent mismatch. The degree of dilution depends on the ratio between mobile phase flow rate (Q mp) and feed rate (Q feed) at which the sample is infused. Our study examined the effect of several parameters on the feed injection of large sample volumes from purely organic diluents in reversed-phase LC. These parameters included the type of diluent, compound retention factor (k), injected sample volume (V inj), and Q mp. With varied Q feed , all compounds revealed a similar range of optimal values for Q r = (Q mp – Q feed)/Q feed between 2 and 5, a range unaffected by V inj and Q mp. For Q r > 5, the slope of the plate height curves (H vs. Q r) decreases with increasing k , potentially extending the range of optimal Q r -values. However, the best Q r -value for a separation is determined by the compound with the smallest k , simplifying optimization. Using feed injection, we were able to reduce plate heights by up to a factor of 8 compared to classic flow-through injection of large sample volumes. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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