Hi,

1) yes.

2) We used to analyze water from concrete that has a similar pH. While I agree with the others that HCl is not a optimal solution it works.
We use a high concentrated HCl and a very small volume (5 uL) on 500 uL sample volume. We also did this with our standards and did not see any changes in O18 values for the standards on our Gasbench system.

Another option is to a higher concentrated CO2 into the vial so that not all CO2 is dissolved in your sample. But, of course, like with  liquid acid you add oxygen to the sample (but since 1 mol equals roughly  22.4 Liters gas this is not so much an issue).

3) I think is should work. I never tried that on our device but I see no reason why not. It might have some corrosion issues so make sure you clean the syringe and autosampler, injection port etc. after that.

regards,

Robert


Am 22.03.2017 um 15:28 schrieb David Gillikin <[log in to unmask]>:

> Dear Isogeochem,
> 
> We are analyzing some difficult deep-sea porewater samples for d18Ow on our Gas Bench II (waters are from serpentinite mud volcanoes). We added 0.5 mL to 12 mL exetainers, flushed them with 0.5% CO2 in He for about 8 minutes, let them sit for more than 24 hours. Some of these do not give any signal on the mass spec. The samples apparently have very high pH and alkalinity – up to a pH of 12.5 and an alkalinity up to 40 mmol/L (and a whole bunch of other odd chemistry). In the same run we’ve analyzed rainwater and standards and all of these are normal – standards were excellent. I don’t think this is a problem with the Gas Bench or MS. 
> 
> My questions are:
> 1) Is it reasonable to think that this water would consume all the CO2?
> 
> 2) How can we work around this? I’m thinking we could add a drop of HCl to the exetainer before flushing to deal with the high alkalinity and pH so we can get some CO2 to stay in the headspace. 
> 
> 3) Are we going to run into trouble when we attempt to analyze these waters for dD on our TCEA? (They have all been filtered though 0.2 um filters).
> 
> Thanks
> Dave
> 
> _____________________________________________________________________
> David P. Gillikin, Ph.D.
> Associate Professor of Geology
> Director: Union Stable Isotope Laboratory
> Union College
> Department of Geology
> 807 Union St.
> Schenectady, NY 12308
> 
> Office phone: (518) 388-6679
> Lab phone:     (518) 388-8741
> email:  [log in to unmask]
> web: http://minerva.union.edu/gillikid/
> Lab Website: http://minerva.union.edu/gillikid/lab.htm
> ______________________________________________________________________
> 

-- 
PD Dr. Robert van Geldern
Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) | GeoZentrum Nordbayern
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