> I am using IAEA-NO3 (+4.7 permil KNO3)as a standard for an EA-DeltaPlus. If
> I use this the N peak gets quite broad (80 seconds) compared to a plant
> sample (55 seconds) and it is tailing much more. If I use IAEA-N1 (+0.4
> permil (NH4)2SO4) I also get a nice peak of 55 seconds. Earlier on I also
> had a nice peak for IAEA-NO3, and now it suddenly has changed, also the
> delta value is changed by ± 0.8 permil. I checked all the reactors and
> traps and this seems OK.
>
> As there is no CO2 peak for KNO3 I can't check on this. I added a little
> carbon to the IAEA-NO3 and then the peak looks a lot better. So the cause
> may be a too slow burning of the KNO3. Does anyone have experience with this?
> Als suggestions are welcome.

Funny you should write this... today I found exactly the same with
NaNO3 and KNO3, poor recovery of N after combustion, but if some
sugar is added things look an awful lot better and recoveries of N
are what I expected.... and the d15N values were quite different...
but the Mg(NO3)2 was the same irrespective of whether I added
sugar.

Expanding the analysis window on the Europa 2020 did not improve
things that much.

My two bits.

Andrew






Dr A.M.Johnston
SPDU
Scottish Crop Research Institute
Invergowrie
Dundee
DD2 5DA
Scotland

Tel No: (44) 1382 562731 ext 3732
Fax No: (44) 1382 562426