Peter, have you tried to use Cu granules from another supplier? We have had similar problems some years ago, but since using Cu from a alternative supplier we havn't seen this although the characteristics of our sample material and other conditions has not changed (mainly plant and soil samples).

Per Ambus, Risø National Laboratory

> -----Original Message-----
> From: Peter Ditchfield
> [mailto:[log in to unmask]]
> Sent: 31 October 2003 12:12
> To: [log in to unmask]
> Subject: [ISOGEOCHEM] reduction tube melt down
>
>
> Dear Listmembers
> We have had a recent spate of Cu reduction tubes becoming blocked by
> some reaction taking place within the copper oxide which is forming as
> the copper becomes oxidised. The system is a Carlo Erba EA attached to
> a Europa geo 20/20 running in continuous flow mode. the reduction
> furnace runs at 600 C.
> Instead of the usual granular copper oxide replacing the granular
> copper we get a black shiny (viterfied) plug of solid copper oxide
> which blocks the He flow  and in bad cases fractures the silica tubing
> of the reduction column.
> There seems to be little pattern as to when it happens and is just as
> likely towards the end of the life of a reduction column as a
> few hours
> after a column change. The vast majority of samples that we
> process are
> collagen.
> Has anyone else had similar experiences? any thoughts on possible
> causes such as excess water in the combustion products?
>
>
> Dr. Peter Ditchfield
> Stable Isotope Laboratory Manager
> Research Laboratory for Archaeology
> University of Oxford
> 6 Keble Road, Oxford, OX1 3QJ, UK
> tel:01865-283647
> fax:01865-273932
>