Metal or other contamination is indicated by a change in retention times, pressure increase, and broadened or skewed peaks. To restore column performance, reverse the column and refer to the Column Cleaning and Regeneration Chart below. If the column back pressure is also high, the flow rate can be reduced until the column back pressure drops (indicating removal of contaminates or particulates). Restore the column to original flow direction and equilibrate with eluent for one hour.To remove organic contamination, pump the columns in reverse flow at 0.1mL/min. with 5/95 acetonitrile/water at 25C for 4 hours. Restore the column to original flow direction and equilibrate with eluent for one hour.No regeneration procedure is available if the column has bacterial growth.