wilkaaro
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AA questions "Closed System"
Does anybody know a closed system AA? Currently I'm working with an open system, the problem is with evaporation I can only load 10-15 samples at a
time. With hundreds of samples to run, I end up staying up all night babysitting an instrument. I know this site is designed for the at home
enthusiast but I really would appreciate a response.
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chemrox
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Why can't you keep your samples stoppered until it's time to run them? Are they in some sort of auto-sampler? If so would cooling the room to say
60F retard the evaporation sufficiently? Could you transfer to a less volatile system? When I was doing work with AA most of my samples were acidic
aqueous solutions. Is your machine heating the sample trays? Is it a new enough machine you could call a rep in to address this? Give us some more
information and maybe we can help.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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wilkaaro
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Right now I do have them stoppered until I run them, I was wondering if there was a way around this. I'm testing silver loads on nitric digested
rubber septa. I can't really cool the room just because our lab is set up in a warehouse set up, there are dividers between the different labs. Its a
shimatzu AA, it doesn't heat the samples, it takes about 7 minutes per sample and I usually have to get through 300 samples during my week. It would
be great to set up 60 or so samples before I leave for the night.
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not_important
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I am not by any means an expert on AA (atoms hadn't been invented when I took chemistry) but in this general situation I would consider using a thin
layer of mineral oil to cover the aqueous solution. Mineral oil is mostly alkanes and a smaller proportion of cycloalkanes, reasonable inert to cold
HNO3 and not likely to contain much metals although obviously blanks would need to be run.
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wilkaaro
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Only problem with the oil is I'm using a graphite furnace I'd be afraid that the oil would screw that up.
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not_important
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Can't say anything about that, but you'd need only a thin layer. How do the samples get stuffed into the furnace?
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Ozone
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There is a sampling robot that pulls up a few uL and deposits it, through a tiny hole into the graphite tube onto a platform inside. Then, the heating
cycle begins 1)dry 2)ash 3)atomize.
It's under argon so it survives being brought to white heat in seconds. The power supply pulls so much juice it humms and rattles when the atomizing
ramp begins.
We put standards in every few samples. These evaporate at the same rate. Our quantitation remains stable overight.
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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wilkaaro
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Alright I'm going to try that tonight, thank you
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not_important
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t`would seem that if the sampler dives deep enough it would go below the oil film with only the amount trapped by the sampling tube being included.
Should be a very small amount, and then surrounded by the nitrate solution which would oxidise it pretty quickly in that environment.
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