It is well known in HPLC that columns packed with smaller particles are more efficient at the expense of higher back pressure compared to columns packed with larger particles. The gain in efficiency is usually traded off by reducing column length, which in turn results in shorter analysis times and lower column back pressure.
Recently, two lines of 5 micron TSK-GEL ODS-100V and ODS-100Z columns were introduced. Based on chemically- inert silica gel, the benefits of these innovative columns have been described in terms of more symmetrical peaks for basic, acidic and chelating compounds. These product lines have now been expanded to include 3 micron packed columns, which are well suited for high throughput LCMS analysis.
Three micron packed columns are now a common tool in many LCMS applications. The data in Figure 1 clearly demonstrates that from a column efficiency perspective, an acetonitrile-containing mobile phase is preferred over one containing methanol of similar solvent strength. The acetonitrile-containing mobile phase also reduced back pressure by about 40% due to lower eluent viscosity, further enabling faster cycle times in high throughput applications. Standard Reference Material SRM 870 was developed by NIST as a means to classify the many commercially available reversed phase columns into groups of closelyrelated columns. Amitriptyline, a strong base, and quinizarin, a chelating compound, are included in the mixture together with more traditional compounds. The symmetrical peaks obtained on TSKgel ODS-100V and TSKgel-ODS100Z columns, as shown in Figure 2 , will simplify mobile phase ma ke up in LCMS and improve the precision of integration.
Figure 3 illustrates this further by allowing the use of a low concentration volatile ammonium formate buffer in the analysis of desipramine, an imipramine metabolite.
Three micron packed TSK-GEL ODS-100V and ODS-100Z columns are effective tools to increase throughput and improve precision in LCMS applications.