Carol,

We routinely analyze water vapor and plant water samples in the 20-30 uL 
range for both HD and 18O.  However, is is quite a demanding procedure. 
Extracting samples this small and getting a droplet of water, then storing 
them and handling them without evaporation is difficult.

We trap vapor samples or distill plant/soil water into glass containers 
that have had the sides "smoothed" by filling them for a few minutes with 
1% HF (caution, HF is a very dangerous chemical but 1% is reasonably safe 
to handle).  If the glass is not "smoothed" then water simply sticks to the 
side of the glass and 20-30 uL samples are unusable as they form small 
droplets on the side of the glass.  On "smoothed" glass water then runs 
down the side of the glass and forms a small droplet that can be pipetted 
into a 100 uL sample vial we use for a Thermo H/Device.  This small vial 
minimizes evaporation of the sample.  The samples are then kept frozen 
until analysis for HD, long term standard deviation external precision of 
plus or minus 0.7 delta D.  Preferably 20 uL, but batches of 10uL can be 
used, of the remaining water is then transferred to a 10mL Exetainer and 
frozen.  These are then kept in a insulated box over dry ice, removed one 
at a time and manually purged for 7 seconds with about 100 mL of 0.2% CO2 
in Helium, then allowed to thaw and equilibrate at room temperature for 7 
days.  They are then analyzed on a Thermo Gas Bench for 18O in the CO2.  We 
have not run enough of these to reliably measure the long term external 
precision, but it appears to be a standard deviation of plus or minus about 
0.12 delta 18O for 20 uL samples, plus or minus about 0.2 delta 18O for 10 
uL samples.  This compares with a long term external precision of plus or 
minus 0.06 delta for 18O with samples over 50 uL.

Hope this helps!

Paul Brooks.






At 08:03 PM 9/27/2007, you wrote:
>Dear All,
>
>Updating the stable isotope lab list on Isogeochem has come at a fortunate 
>time for me; as I am searching for a suitable laboratory to outsource the 
>isotopic analysis of all our atmospheric water vapour and plant samples.
>We have been on a week long field campaign and have numerous samples which 
>require delD and del18O analysis; 162 atmospheric water vapour samples; 
>microliter volumes and 252 plant samples which are currently being 
>distilled by cryogenic vacuum distillation in our laboratory.
>Trying to filter through every lab listed on the Isogeochem website would 
>be a timely exercise; it would be great if someone could advise me with 
>regards to which laboratories are capable of analysing these small volume 
>samples, with what accuracy and the expected turnaround time.
>
>Your assistance would be greatly appreciated!
>
>Carol Tadros
>Stable Isotope Chemist
>Institute for Environmental Research, ANSTO
>PMB 1, Menai NSW 2234, Australia
>P: +61 2 9717 3506
>F: +61 2 9717 9260
>E: <mailto:[log in to unmask]>[log in to unmask]
>
>"Important: This transmission is intended only for the use of the 
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>

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