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Ruta, Did you bake the GFF filters before you used them?
Bob
----- Original Message ----- 
From: "Ruta Bariseviciute" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, January 27, 2013 9:56 AM
Subject: [ISOGEOCHEM] Problems with GF/F filters measurements


> Dear All,
> I have problem with measurements of GF/F filters.  My samples are 
> freshwater lagoon sediments. Nitrogen isotope ratio  +20‰. We have Delta V 
> Advantage and FlashEA1112. Salt concentration in the samples is very law. 
> I removed carbonates keeping filters in desiccators with concentrate HCl. 
> After 4 hours I kept my filters in 50oC  for about 24 hours. I always was 
> using this method and didn’t have any problems. Can it be chlorine? Maybe 
> I had to keep filters in fume hood for Cl evaporation? Or maybe may GC 
> column is “tired”. I had cleaned GC column by increasing its temperature. 
> I also replaced the oxidation column filling it with double dose of 
> silvered cobalt oxide. It didn’t help. I also replaced magnesium 
> perchlorate column. The measurements of the other samples (not filters) 
> are good.  If it is chlorine, what should I do with these filters?
> Thanks,
> Ruta
>