I have inherited a filter on one of our 50X2.1mm columns.1) Why and when is a filter useful?2) How do I test whether the filter is fulfilling my expectations? Are there additional tests to ensure the filter has not begun doing additional tasks?Thanks,JackemeyerTempe, AZPS I searched "filter" and read the relevant discussions. If this question has been answered, please feel free to simply redirect me and others to the approriate link.PPS When I "start a discussion", two options are available -- what is "start a new project"? What are projects and where can I find them? Are they searchable? Are they public or private?