The problem with splitt peaks can occur due to following reasons:
a) Contamination on column or guard column. Solution: Remove guard column if present and attempt analysis. Replace guard column if necessary. If analytical column is obstructed, reverse and flush. If problem persists, column may be clogged with strongly retained contaminants. Use appropriate restoration procedure. If problem still persists, replace column. b) Sample solvent incompatible with mobile phase. Solution: Adjust solvent. Whenever possible, inject samples in mobile phase. c) Small void at column inlet. Solution: Repack top of column with particles of same bonded phase functionality. Continue using column in reversed flow direction. d) Partially blocked frit. Solution: Replace frit. e) Column bed is broken. Solution: Replace column.