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Shesha,

High water background could also cause drift in your reference peak values.

Paul Eby
University of Victoria

At 03:27 AM 30/03/2008, you wrote:
>Dear All,
>
>I have been measuring carbon and nitrogen isotope ratios using my 
>Delta Plus IRMS (Thermo) interfaced with a Flash elemetal analyser 
>(EA1112) through Conflo III.  Recently, I noticed an unique 
>problem.  The two reference gas injections used to give me a std 
>dev. better than 0.06 permill. But now, the std dev are pretty 
>bad.  I tried tightening the capillery ferules at the Conflow 
>interface.  The areas of masses 44, 45 and 46 are not very bad, they 
>are not exactly same!  Can this small change in area cause a huge 
>shift in std dev of the isotope measurements?  Has anyone 
>encountered a similar problem?  Please can you suggest a solution to this?
>
>Thanks and regards,
>Shesha
>
>Dr. M.S. Sheshshayee
>Associate Professor
>Department of Crop Physiology
>University of Agricultural Sciences
>GKVK Campus, Bangalore 560 065
>INDIA
>
>Ph(W): +91-80-2362 0737
>Ph(H): +91-80-2363 6414
>Mobile: 93425 90578
>
>
>
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