Hello Ty,
There is a discussion regarding ChromHD and brine samples in the paper
we did with John Morrison:
"On-line high precision stable hydrogen isotopic analyses on nanoliter
water samples - J. Morrison, T. Brockwell, T. Merren, F. Fourel and A.M.
Phillips - Analytical Chemistry Vol 73, Number15, Pages 3570-3575".
I am not running brine samples here with my MultiPrep, but I remember
from the numerous equilibration experiments we did with John, we
sometimes had surprises with H2O-H2 equilibration reactions. If the
water to equilibrate is not pure, the catalysts seem to be sometimes
affected and the D/H numbers can become very erratic.
We even had the case once on waters extracted from plants where
equilibration got us nowhere whereas EA-ChromHD on the same waters gave
beautiful numbers.
Regards,
--
François FOUREL
UMR CNRS 5125 PEPS
Université Claude Bernard Lyon 1
2 rue Raphaël Dubois - Bât. Géode
F-69622 VILLEURBANNE Cedex - FRANCE
Tél : +33 (0) 4 72 44 62 42
FAX : +33 (0) 4 72 43 16 88
Email : [log in to unmask]
Tyler B Coplen a écrit :
>
> Dear Paul and Wolfram,
>
> I was not issuing a concern about memory due to sample carryover in the
> syringe from one sample to the next, which has been discussed on
> ISOGEOCHEM, nor about analysis of precipitation samples.
>
> Rather, unless the proper precautions have been taken, I am concerned
> about recommending the TC/EA technique or ChromHD technology for delta
> H-2 measurements to those who analyze ground waters, saline waters, or
> brines containing ions whose salts have water of hydration. Luckily for
> some laboratories, they never analyze such waters and this e-mail does
> not apply to them.
>
> Unfortunately, many of the most interesting waters in geochemistry and
> geology are saline waters or brines composed of salts having waters of
> hydration. Some of these salts can be dehydrated. Calcium sulfate
> dihydrate (gypsum) dehydrates completely at 163 degrees C. Calcium
> chloride hexahydrate and magnesium sulfate septahydrate both dehydrate
> completely at 200 degrees C. But some salts with waters of hydration
> are more problematic. Magnesium chloride hexahydrate does not dehydrate
> with increasing temperature. Rather, it decomposes, giving off HCl at
> 116 degrees C.
>
> One can imagine that putting calcium/magnesium chloride/sulfate waters
> into a reactor can provide the opportunity for large between-sample
> memory unless all salt formed during flash evaporation of a sample is
> maintained above its dehydration temperature. The more samples that are
> analyzed, the larger the memory. What one would like to do is to
> maintain the bottom of the septum and the injection volume at a
> temperature greater than degrees C. In this manner, only magnesium
> chloride will be a problem and most other salts will be dehydrated.
>
> What I am wondering is how Willi and Giorgio tackle this problem.
>
> I should mention that because we analyze such brines and saline waters,
> we prefer dual-inlet Pt equilibration.
>
> Ty
>
>
>
> *Paul Brooks <[log in to unmask]>*
> Sent by: Stable Isotope Geochemistry <[log in to unmask]>
>
> 02/17/2006 05:53 PM
> Please respond to
> Stable Isotope Geochemistry <[log in to unmask]>
>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> Re: syringe memory
>
>
>
>
>
>
>
>
> Ty,
>
> We were able to eliminate the memory effect of syringe injection on an
> H/Device by using a dry ethyl ether rinse between samples. I think
> since we started this others are now using alcohol or carbon
> tetrachloride, but the principle is the same. Rinsing the syringe with
> a dry compound that is an azeotrope and injecting the waste to a modest
> house vacuum dries the syringe completely. We keep the ethyl ether in a
> vial with a septa to stop it evaporating, then inject to a waste
> position that is a septa with the house vacuum on the other side of the
> septa. Even as the syringe goes into the waste septa one sees the ethyl
> ether blow out of the syringe even before the plunger comes down.
>
> Having said that, the syringes we use gradually oxidize and have to be
> replaced every 200 injections. I have also only run a few sets of sea
> water, but saw no memory effect going from the sea water to the
> standards in fresh water.
>
> I can provide more details if anyone is interested. Paul Brooks
>
>
>
>
> At 09:35 AM 2/17/2006, you wrote:
>
> Dear François,
>
> With the ChromHD technology, how are you solving the between-sample
> memory problem for brine and sea water samples?
>
> Ty
>
> *
> Francois Fourel <[log in to unmask]>*
> Sent by: Stable Isotope Geochemistry <[log in to unmask]>
>
> 02/17/2006 03:33 AM
>
> Please respond to
> [log in to unmask]
>
>
> To
>
> [log in to unmask]
>
> cc
> Subject
>
> Re: Gas Bench hydrogen measurements
>
>
>
>
> I'd like to add a few comments to Willi's email.
> As far as D/H is concerned I fully agree that continuus flow is now
> giving the best precision for water analyses. My experience is that a
> Eurovector EA with ChromHD technology generates D/H precisions better
> than 0.5permil which is better than what we get with our MultiPrep/DI
> system (usually 1permil). As far as 18O is concerned our experience here
> is that we get reproducibilities better than 0.05permil using CO2-H2O
> equilibration with our MultiPrep-DI system. For some applications going
> from 0.1 to 0.05 can make a significant difference.
> Another parameter to take into account when doing 18O with an EA is that
> as soon as you will mention the name "carbon monoxide", the health and
> safety officer of your university will be on your back. Depending on the
> legislations, there are almost always solutions, but CO2 equilibration
> is more "health and safety-friendly".
> Our experience in short is that for best isotopic determinations with
> waters we prefer D/H with an EA but 18O with DI equilibration.
>
> Regards,
>
> --
> François FOUREL
>
> UMR CNRS 5125 PEPS
> Université Claude Bernard Lyon 1
> 2 rue Raphaël Dubois - Bât. Géode
> F-69622 VILLEURBANNE Cedex - FRANCE
>
> Tél : +33 (0) 4 72 44 62 42
> FAX : +33 (0) 4 72 43 16 88
> Email : [log in to unmask]
>
> Willi A. Brand a écrit :
> > Hi,
> > I just would like to comment to Anindya's remark that "/certainly TCEA
> > cant be an alternative to more precise gas bench/". The daily routine
> > precision in our TC/EA is 0.5 per mill for D/H from water samples. We
> > run more than 200 injections per day with a net of 30 samples, each of
> > them injected 3 times. The other half of the injections is standards
> > (the sequences are optimized for performance, not throughput; given the
> > precision we could afford to inject each sample only once, increasing
> > the net number of samples processed for D/H to 90 on a single mass
> > spec). For 18O, precision is in general better than 0.1 per mill with
> > fewer injections due to the longer elution time of the CO. With a single
> > glassy carbon tube we have made more than 3000 injections.
> > My conclusion: This is my method of choice for the times to come. It is
> > so much more convenient compared to all other techniques (I think I have
> > tried them all) with zero compromise in precision.
> > Willi
> >
> > Anindya Sarkar wrote:
> >
> >> Hi Penny
> >> With a relatively new machine and gas bench we get typically 1.5 %o SD
> >> that is the kind of SD one gets in dual inlet as well. But we have
> >> been able to bring it down to even 1 %o level also. I hope u are using
> >> a fixed volume of water (we use 500ul and our experiments show that if
> >> you go below 200ul, values systematically change). we also bake the
> >> column after say about every 100 samples. But ur problem it looks more
> >> with platinum catalyst. The sticks supplied by thermo are not like
> >> hokko beads but a thin coating. we have reused each for at least 10
> >> analyses and yet got very good results. but we also noticed that from
> >> some sticks coatings are peeling off. why not try with absolutely new
> >> sticks and run several of ur lab standards and see the
> >> reproducibility? as i understand TCEA will have more errors than gas
> >> bench (~2%o) but we got ~3%o on limited analyses; possibility of water
> >> evaporating in up part of furnace b4 it reacts. certainly TCEA cant be
> >> an alternative to more precise gas bench.
> >> ---------------------------------------------------------------------
> >> Anindya Sarkar
> >> Associate Professor
> >> National Facility of Stable Isotope Geochemistry
> >> Department of Geology and Geophysics
> >> Indian Institute of Technology
> >> Kharagpur 721302
> >> West Bengal, INDIA
> >> Tel.: 0091-3222-283392 (O) 283393 (R) 220184 (R)
> >> Cell: 09434043377
> >> Fax.: 0091-3222-282268
> >> _http://anindya-sarkar.tripod.com_ <http://anindya-sarkar.tripod.com/>
> >> ------------------------------------------------------------------
> >> ----- Original Message ----- From: "Penny Higgins"
> >> <[log in to unmask]>
> >> To: <[log in to unmask]>
> >> Sent: Friday, February 17, 2006 3:57 AM
> >> Subject: [ISOGEOCHEM] Gas Bench hydrogen measurements
> >>
> >>
> >>> Hello Isotopers,
> >>>
> >>> We've been attempting to use our Gas Bench to do hydrogen analysis of
> >>> waters using platinum catalysts and headspace equilibration at about
> >>> 32degreesC. When we started, we got acceptable numbers with good
> >>> within analysis (10 peaks) standard deviations. Values plotted
> >>> sensibly along (or very near) the meteoric water line. As time went
> >>> on, our standard deviations have gotten much worse (as much as 7
> >>> permil) and our data very seldom plot reasonably close to the
> >>> meteoric water line. Often, hydrogen data plot well above the
> >>> meteoric water line. We have gotten great results from oxygen
> >>> analyses of the same samples.
> >>>
> >>> We've just spent a great deal of time and effort to ensure that our
> >>> sample gas is totally dry before it enters the mass spectrometer. I
> >>> also let the catalysts sit in our oven (60degreesC) for two days
> >>> before placing them into the vials with our water samples. We got
> >>> better standard deviations for our analyses this time (between 2 and
> >>> 3), but still have unreasonable scatter around the meteoric water line.
> >>>
> >>> Questions:
> >>>
> >>> 1) What is a generally acceptable standard deviation for d2H from
> water?
> >>>
> >>> 2) Could the problem be with our catalysts? I thought that, by
> >>> definition, catalysts were reusable .. but maybe not. We've only done
> >>> about 5 analyses with each catalyst.
> >>>
> >>> 3) Are we going to have this same problem when we start running
> >>> waters using our TC/EA instead? or are we going to be happy that we
> >>> made the change?
> >>>
> >>> If anyone out there in cyberspace has dealt with and corrected this
> >>> problem, we would love to hear from you!
> >>>
> >>> Thanks,
> >>>
> >>> ~Penny
> >>>
> >>> *******************************************************************
> >>> Dr. Pennilyn Higgins
> >>> Research Associate
> >>>
> >>> "SIREAL"
> >>> Stable Isotope Ratios in the Environment Analytical Laboratory
> >>>
> >>> Department of Earth and Environmental Sciences
> >>> University of Rochester
> >>> 227 Hutchison Hall
> >>> Rochester, NY 14627
> >>>
> >>> [log in to unmask]
> >>>
> >>> Office: 209b Hutchison Hall Lab: 209 Hutchison Hall
> >>> Voice : (585) 275-0601 Outer lab: (585) 273-1405
> >>> FAX : (585) 244-5689 Inner lab: (585) 273-1397
> >>>
> >>> _http://www.earth.rochester.edu/SIREAL/index.html_
> >>> *******************************************************************
> >>>
> >>>
> >>>
> >>> --
> >>> No virus found in this incoming message.
> >>> Checked by AVG Anti-Virus.
> >>> Version: 7.0.344 / Virus Database: 267.15.6/257 - Release Date:
> >>> 2/10/2006
> >>>
> >>>
> >>
> >>
> >
> > --
> > .....................................................................
> > Willi A. Brand, Stable Isotope Laboratory [log in to unmask]
> > Max-Planck-Institute for Biogeochemistry (Beutenberg Campus)
> > Hans-Knoell-Str. 10, 07745 Jena, Germany Tel: +49-3641-576400
> > P.O.Box 100164, 07701 Jena, Germany Fax: +49-3641-577400
> > _http://www.bgc-jena.mpg.de/_
> > _http://www.bgc-jena.mpg.de/service/iso_gas_lab/_
> > .....................................................................
> > GASIR 2005 in Jena:
> > _http://www.bgc-jena.mpg.de/service/iso_gas_lab/gasir2005/index.shtml_
> > .....................................................................
> >
>
> --
> François FOUREL
>
> UMR CNRS 5125 PEPS
> Université Claude Bernard Lyon 1
> 2 rue Raphaël Dubois - Bât. Géode
> F-69622 VILLEURBANNE Cedex - FRANCE
>
> Tél : +33 (0) 4 72 44 62 42
> FAX : +33 (0) 4 72 43 16 88
> Email : [log in to unmask]
>
> Center for Stable Isotope Biogeochemistry
> Valley Life Science Building Room 3060
> Integrative Biology - MC3140
> Berkeley CA-94720
> Phone: (510)-643-1748
> Fax: (510)-643-1748
>
--
François FOUREL
UMR CNRS 5125 PEPS
Université Claude Bernard Lyon 1
2 rue Raphaël Dubois - Bât. Géode
F-69622 VILLEURBANNE Cedex - FRANCE
Tél : +33 (0) 4 72 44 62 42
FAX : +33 (0) 4 72 43 16 88
Email : [log in to unmask]
|
