For research use only. Not for use in diagnostic procedures.
The analytical column was replaced after the ion ratios were failing. Even after equilibrating the column by running the LC method for 45 mins and running a system suitability test for 30 mins, the peak shape was poor.
The analytical and guard columns should be replaced at the same time to avoid the issue of poor peak shape.
Most analytical columns are replaced every 1500-2000 injections; while guard columns should be replaced every 100-200 injections. While this can vary between systems, replacement of columns and guard columns at routine intervals will reduce this issue. Additionally, the analytical column will need to be equilibrated before it can be put into routine use. This equilibration can be accomplished by making repeat injections on the column of a system suitability test (SST) standard, but specific instructions on how to equilibrate your column should be provided by the column manufacturer. While some columns require special equilbration processes, most columns used in clinical applications (phenylhexyl, biphenyl) can be installed and 2-3 injections of blank (or SST) later be used.