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Volume 35, Issue 12
A revolutionary new inline static mixer has been developed and specifically tailored to meet the exacting demands of HPLC and UHPLC systems. Poor mixing of two or more mobile phase solvents results in a high signal to noise ratio and, thus, decreased sensitivity. The test data presented demonstrates that superior mixing is achieved while minimizing the internal volume in various gradient test conditions, such as unparalleled mixing for trifluoroacetic acid (TFA) and water and acetonitrile gradients.
Low mixing efficiency, resulting in poor signal-to-noise ratios, has plagued the chromatography world when it comes to limits of detection and sensitivity. If poor mixing is present, baseline noise will appear as a sine wave (rise and fall) of the detector signal versus time. Poor mixing will also broaden and create asymmetrical peaks resulting in reduced column efficiency and peak resolution. The ideal static mixer will combine the advantages of high mixing efficiency, low dead volume and low pressure drop, while minimizing the volume and maximizing the throughput of the system.
Figure 1: Schematic diagram of the low-pressure gradient experimental test system.
The following HPLC conditions and test setup were employed to measure the system baseline noise and to compare the relative performance of various static mixers. Figure 1 shows a schematic diagram of a typical HPLC and UHPLC system configuration. Static mixer testing was performed by locating the Mott PerfectPeak® static mixer immediately downstream of the pump and upstream of the sample injector and HPLC column. For this study, mixing efficiencies were performed by bypassing the sample injector and column using a capillary tube between the static mixer and the UV detector to create back pressure.
Figure 2: Plots showing offset HPLC UV detector signal versus time for this study showing baseline noise with no mixer, and Mott 25 µL, 50 µL, 100 µL, 150 µL, and 300 µL mixers.
The HPLC system utilized for this testing was an Agilent 1260 Series HPLC with a UV detector controlled using Agilent Chemstation Software. Table I contains the setup conditions used in this study.
This application note demonstrates that greater mixing efficiency is exhibited with every Mott PerfectPeak® static mixer volume increase with respect to the system with no mixer. Greater than 95% reduction in baseline noise was achieved with the largest size mixer which will result in improved limits of detection and sensitivity.