By Jason G on Wednesday, August 4, 2004 - 08:17 am:

Im using two 5890's tandom. The ECDs on both have simutainously degraded since the introduction of a new N2 tank. However the signal on the first GC in line is at about 3000 Hz, while the second is at 800 Hz. Both signals are higher than usual but the first is off the charts. I have done all the normal preventive maintence and a new N2 will be in today. Any suggestions?

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By xxx on Wednesday, August 4, 2004 - 12:30 pm:

Water or Oxygen cause high baseline.
Perhaps your tank contaminated or the purity bad.

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By john acton on Thursday, August 5, 2004 - 06:10 am:

If the baseline increases with the column ramping then you may have some severs contamination on your column. Try removing the columns from the ecds and look at the baselines. If they remain high and show no sign of dropping down to normal then the likely source of contamination is the new n2 cylinder. We use the chrompack charcoal filters on the nitrogen line and this goes from green to black when exposed to oxygen. You can check that as well if you have such a filter. Baking out an ecd cell after gas or water contamination does not always work. As a matter of interest do you get negative spikes during your chromatographic run?

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By Jason G. on Thursday, August 5, 2004 - 06:19 am:

JOHN,
Yes as a matter of fact small negative spikes are appearing throughout the run.

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By Jason G. on Thursday, August 5, 2004 - 06:30 am:

thank you for your help
the new N2 arrived and the signal is declining. I have ordered the chrompack filters as to prevent this problem

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By Jason G. on Thursday, August 5, 2004 - 06:42 am:

one more question
how long before the signal stabalizes?

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By xxx on Thursday, August 5, 2004 - 07:55 am:

i use also the chrompack filter.
good to see that get better with your new tank!

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By xxx on Thursday, August 5, 2004 - 07:59 am:

hi jason
the charcoal filter is black and has no indicator,the oxygen filter goes green to black if contaminated.
Moreover i use only a moisture trap on the N2 line

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By Jason G. on Thursday, August 5, 2004 - 08:06 am:

the signal did drop initally, but it rose again after the first injection. there has been some improvement but not much. Should i bake the ecd?