Dear François, You have not made me rest any easier. Yes, there is a discussion about the ChromHD and brine samples in Morrison et al., but there is only discussion and no solution to the problem. I am still 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. Ty Francois Fourel <[log in to unmask]> Sent by: Stable Isotope Geochemistry <[log in to unmask]> 02/20/2006 10:13 AM Please respond to [log in to unmask] To [log in to unmask] cc Subject Re: Gas Bench hydrogen measurements 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]