We own one of those acid pumps. With a new Gas Bench, colleagues  
strongly advised us to go with the human approach--a needle, an arm,  
and a syringe. I think it works pretty well and comes under the  
category of "Good, Fast, and Cheap".

Marilyn Fogel


On Nov 29, 2006, at 3:34 AM, Geldern, Robert van wrote:

> Greetings,
> Finnigan changed the design of the acid needle in the Gasbench.
>
> The new needle is thinner and very flexible.
> However, the drops are smaller than using the old, thick needle.
> Due to the smaller drops it seems that more drops are necessary for  
> the
> complete reaction of the carboante sample. Dropping of 5 to 8 drops  
> does
> not work, since the acid volume transfererd into the vial is to small
> and the sample is not dissolved at all or only in parts.
>
> So, we incereased the number of drops up to 15. Consequently, the
> dropping times increases dramatically. This causes another problem:
> Due to the long dropping time the CO2 in the vial to be measured (with
> sample needle in) is already diluted by the helium flow into the vial.
> So the CO2 does not last for 10 sample peaks.
>
> I incereased the volume of the acid pump to maxium (450mikroliter per
> stroke). It still takes 20 strokes per drop!! So for 15 drops you will
> need 300 strokes...
>
> Any suggestions?
>
>
> Robert
>
>
> -- 
> Dr. Robert van Geldern
> Leibniz Institute for Applied Geosciences (GGA)
> Section 3: Geochronology and Isotope Hydrology
> Stilleweg 2, 30655 Hannover, Germany
> phone: ++49-511-643-2313
> mailto:[log in to unmask]