Hi Eshani,

What kind of TOC analyzer are you using...a combustion, chemical, or membrane type?  Each of these can have unique issues that might cause that behavior.  Combustion analyzers can get fouling on the catalyst that could conceivably cause high baseline, although a sustained 50% increase in baseline is unusual.  Chemical oxidation analyzers may show that behavior if the flowrate of persulfate through the cell is hampered, especially after analysis of a sample containing high amounts of humic material.  There may also be an electronic reason, such as an incorrectly configured autozeroing function that resets the zero at a specific time after each injection.  If it resets this after the analysis of a sample with hugely tailing peaks, it also could result in a the baseline appearing to go negative.   

Hi, Joe,

Thank you for the information.

I am using a combustion type. I was using high sensitivity catalyst. Then I changed it to Pt catalyst and tried. It still gives me high baseline. If this is due to an electronic reason, how can I fix it? Thank you again. 

Eshani

Hi, Solution was found. The TOC unit has 2 water bottles, 1 was hidden. It should be filled in order to get the correct baseline.