Karen,

On my PrismIII I have the 'Min inlet pressure' set to 10mbars and that
is fine. I could go to about 5-7mbar but the beam sizes get a bit
small. I can run samples down to about 20ug but I get concerned about
samples smaller than about 30ug. If you run such small samples you
should run some standards of about the same size. I have lengthened the
reaction time from the default 13min to 15min. I also increased the
'Time for thermal equilibration' to 240sec and the 'Temperature to stop
heater' is down to -50. This is to try and stop the sample gas from
getting too hot as that upsets the beam balancing: the target beam is
measured with the gas hot but by the time the ref has been balanced to
that target the sample gas has cooled and so the beam is smaller. I
think all other settings are still default.

cheers,
David


Francois Fourel wrote:

> Hello Karen,
>
> We are using a MultiPrep for carbonats here in Lyon.
> When you are in MassLynx if you look in the window called "Inlet Params"
> in your inlet editor you will find a parameter called "Min inlet press
> (mBar)" which you can modify. This is the limit used by the system to
> decide how to run the sample. After the sample has been reacted, the CO2
> is trapped in the external cold finger. Then the external cold finger is
> heated and the CO2 is released. The transducer reads the pressure from
> the sample CO2 and compares it with this parameter. If it is lower, it
> will use the inlet cold finger, if it is above, it will run the sample
> through the bellow.
> Ours is set to 20 mbars.
>
> The best way to optimise the preparation parameters is to start from the
> default ones, modify them one by one and see how it affects your results.
> Our experience is that the default pumping times and transfer times seem
> to be a bit short and we have doubled most of them as a safety.
>
> The reaction time may have to be adjusted depending on the type of
> sample you run. The default one has been calculated for pure calcite.
>
> The quality of your phosphoric acid will be an important parameter and
> the acid delivery line is a critical part of the system.
>
> We have been happily running mostly big samples 100ug and above.
>
> Hope it helps,
>
> --
> 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]
> Karen Leslie a écrit :
>
>> Hi everyone,
>>
>> Does anyone have any experience running carbonates using MassLynx
>> Multiprep
>> system. Ours is running a Gilson Autosampler connected to an
>> IsoPrime-DI.
>>
>> I was particularly interested in the way the system decides when to
>> freeze
>> down samples into the internal coldfinger and how to decide what are the
>> optimum preparation parameters and inlet parameters to use. What sort of
>> sample sizes do people run? Any other relevant info would be greatly
>> appreciated.
>>
>> Many thanks,
>> Karen
>>
>>
>> Dr Karen Leslie
>>
>> Earth Sciences
>> University of Queensland
>> St. Lucia, Qld, 4072
>> Australia
>> E-mail: [log in to unmask]
>> www.earth.uq.edu.au
>> Tel: +61 7 336 51132 / 53281
>>
>>
>


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David Wheeler

Professional Officer
Geochemistry Laboratory
School of Earth and Environmental Sciences
University of Wollongong,
Wollongong, 2522, NSW
Australia

Phone 02 4221 4586 (office)
        02 4226 5903 (lab)
Fax 02 4221 4250

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