Trouble with a Negative peak

[fenmick]

My chromatogram shows a 5-10 mV neon (neg) peak. Integration is usually from the lowest point of this (neg) peak to baseline, about 0.6 min downfield. This gives me a very large triangle of area, and eliminates later detections.

What is my best course?

[Daniel Mentlik]

Dear Kelly,
can you send us an example chromatogram showing this to support@dataapex.com?

Just from hearing this, I might suggest two ways how to automatically repair the integration (in order of preference):

• define Integration Interval (or intervals) for the chromatogram, so that the peaks of interest are in the interval and the negative peak is not.

or

• use the the Baseline Lock function for that peak - once again after selecting the function, set the interval around the negative peak, which then won't be integrated.

Both approaches suppose that the retention time of said negative peak is reproducible enough and that the negative peak is sufficiently resolved from positive peaks. The problems when the retention times are not reproducible can be reduced by usage of reference peak (which will somewhat match the real positions of peaks to expected positions).

Please check this topic of Clarity Guide for details on the procedure. After applying this function in the chromatogram, it is necessary to transfer the integration table back to method so that next chromatograms will be measured and negative peak is automatically not integrated. This is done by either copying the contents of integration table or by saving the chromatogram method as a template method. It is also possible to automatically Batch-process all already measured chromatograms.