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Agreed Patrick, very interesting!


To summarize it seems like the best course of action is:


(1) bake the capsules - regardless of age - in a muffle furnace or ideally a vacuum oven at temperatures between 300 and 550 C for several hours.


(2) weigh in the samples as soon as possible using smooth forceps.


(3) place the wrapped samples in a desiccator (or maybe back in the vacuum oven at low temperature?) until loading the autosampler.


As for the blank increasing after baking, John I'm curious about what happened to your capsules between leaving the furnace and entering the autosampler. I can imagine water vapor adsorbing quickly onto the capsules after being moved outside the furnace.


The Brand et al. 2009 paper (RCM 23: 999-1019) mentions flushing the samples with helium for two hours after loading the Zero Blank autosampler. It's anecdotal, but I tried this yesterday and got undetectable (< 50 mV) peaks for my three unfurnaced blanks. Maybe adsorbed water is a bigger problem than oxidation.


----------------------------

Jordon Munizzi, PhD

Research Facility Manager

[cid:c53f8e9b-1fa0-4bf5-8451-8c34bf3ce698]

Department of Earth and Environmental Sciences

University of Kentucky

Ph: (859) 270-9177

Fax: (859) 323-1938

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isotopes.as.uky.edu<https://isotopes.as.uky.edu>

________________________________
From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Patrick Griffin <[log in to unmask]>
Sent: Wednesday, December 5, 2018 9:52:46 PM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] Oxidized silver capsules

This is an interesting conversation.

I have tried baking at 350 and 550 (both in air), and I had no problems at either temperature, including the sticking to either one another or the glassware.  They weren't especially tightly packed; they were in a single layer, right-side up in a glass petri dish.  This has always been convenient for me, because it means I can put them in with a batch of glassware and get all of my baking done at once, which is that perfect marriage when efficient meets lazy.

-patrick



Patrick Griffin
Department of Earth and Atmospheric Science
1001 E 10th Street
Bloomington IN 47408