Dear Wolfram, David, Qui and all.

Many thanks for your help, yes my focus will be on d34S initially.

Thanks again,

Daniel


"Wolfram Meier-Augenstein (aps)" <[log in to unmask]> escribió:

> Dear Daniel,
>
> David has a fair point here; d34S should not be affected unless
> phosphate or its thermolysis products have an effect (a) on
> quantitative conversion of [SO4]2- into SO2; (b) on EA reactors; (c)
> downstream of the reactors (GC-column; water trap).
>
> Admittedly, in my initial response to your question I was focusing on
> the effect on 16O/18O abundance ratios of sulphate given the
> commonality between sulphates, phosphates and nitrates as matrix for
> 18O analysis.  In contrast, for 34S analysis I automatically think of
> silver sulphide as being typically used.  Of course your sample
> sulphur is present as sulphate so precipitating sulphides won’t work.
> ;-)  Apologies for any confusion I may have caused.
>
> That being said, depending on how your instrument deals with 18O
> correction, the “alien” oxygen contribution from barium phosphate
> (and possibly barium nitrate) may skew your d34S data.  On the other
> hand, if the plan is to drop the samples in a standard EA reactor,
> the oxygen background from the reactor chemicals will more than
> likely outweigh any additional O contribution from phosphates (and
> nitrates).
>
> Since in sulphate, sulphur is present in its highest state of
> oxidation (+VI), running sulphates through an EA relies on
> thermolysis (of [SO4]2- into SO2 and O2) rather than combustion in
> the classical sense (given the oxidation state of S in SO2 is +IV).
> In analogy to the nitrate EA-IRMS method described by Gentille and
> Siegwolf, it might be a good idea to run your samples with the O2
> pulse turned off (so as to favour the break-up reaction of [SO4]2-
> into SO2 + O2).
>
> Best,
>
> Wolfram
>
>
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
> Behalf Of David Psomiadis
> Sent: 12 May 2016 13:26
> To: [log in to unmask]
> Subject: Re: [ISOGEOCHEM] BaSO4 analysis interferences in water samples?
>
> Dear Daniel,
>
> Humbly trying to add a comment to the previous answers, in contrast
> to δ18O, your δ34S should not be critically affected by the presence
> of other salts in the sample (NO3, PO4 etc), during the precipitation
> of BaSO4.
>
> Cheers
>
> 2016-05-12 14:05 GMT+02:00 Qi, Haiping
> <[log in to unmask]<mailto:[log in to unmask]>>:
> Dear Daniel,
>
> You may also get some idea from Janet Hannon and others'  paper
>
> "Effects of nitrate and water on the oxygen isotopic
> analysis of barium sulfate precipitated from
> water samples",  published on RCM 2008, 22: 4109-4120
>
> Cheers,
>
> Haiping
>
> On Thu, May 12, 2016 at 6:53 AM, Daniel Carrizo
> <[log in to unmask]<mailto:[log in to unmask]>> wrote:
>
> Dear ISOGEOCHEM colleagues,
>
> I precipitate sulphate with BaCl2, for d34S measurments, I know that
> I have some other ionic species in the water sample, like phosphate,
> or nitrate, thus I have to expect interferences/problems in the BaSO4
> IRMS analysis??
>
> Many thanks for your help and thoughts!
>
> Daniel
>
> Dr. Daniel Carrizo
> Investigador Ramón y Cajal (RYC)
> Centro de Astrobiología (INTA-CSIC)
> Instituto Nacional de Técnica Aeroespacial
> Ctra de Torrejón a Ajalvir, km 4
> 28850 Torrejón de Ardoz, Madrid, Spain.
> Tel: (+34) 692521256<tel:%28%2B34%29%20692521256>
>
> Email: [log in to unmask]<mailto:[log in to unmask]>
>
>
>
>
>
> --
> Haiping Qi
>
> USGS/Reston Stable Isotope Laboratory
> 12201 Sunrise Valley Dr., MS 431
> Reston, VA 20192
>
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> email: [log in to unmask]<mailto:[log in to unmask]>
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>
>
>
> --
>
> Dr. David Psomiadis
> Laboratory Manager
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Dr. Daniel Carrizo
Investigador Ramón y Cajal (RYC)
Centro de Astrobiología (INTA-CSIC)
Instituto Nacional de Técnica Aeroespacial
Ctra de Torrejón a Ajalvir, km 4
28850 Torrejón de Ardoz, Madrid, Spain.
Tel: (+34) 692521256
 
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