Purely based on the chromatography (the 28/29/30 peak shortly followed not
by a bear but a 30 peak) I'd say you are looking at NO+.
The main reason is incomplete reduction but the question is why? One
possible cause could be a problem with the O2 pulse (too much or an O2 leak
into the EA) which causes your reduction tube to expire before its time.
Another reason would be a problem with the reduction stage such as
temperature or the copper filling.
Just to cover all bases, you are happy the water trap isn't spent?
> -----Original Message-----
> From: Stable Isotope Geochemistry
> [mailto:[log in to unmask]] On Behalf Of Allison Burnett
> Sent: 28 August 2006 17:18
> To: [log in to unmask]
> Subject: Unexpected Mass 30 Peak
> I am currently running sediment samples in tin capsules in an
> elemental analyzer (Costech ECS 4010) connected through a
> ConFlo to a MAT 252 Finnigan Mass Spectrometer.
> After changing out the oxidation and reduction columns in the
> EA, we are now getting a high mass 30 peak for an unknown
> reason. I'm assuming the peak is from NO+, but I can't
> figure out why, or how to fix it.
> I have included links to two pictures taken by screen capture
> from the EA software.
> I apologize about the resolution of these images. The first
> image is the signal from a blank (a tin capsule with nothing
> inside of it.) The first two peaks are from the nitrogen
> standard gas, and the last three peaks are from the carbon
> dioxide standard gas.
> The second image is from an Acetanilide sample, also run in
> tin. I ran several blanks interspersed with the Acetanilide
> samples, each blank and each Acetanilide sample looked the
> same as these two images. As before, the first two peaks are
> the nitrogen standard gas. The third peak is the nitrogen
> signal from the Acetanilide; although it is hard to see in
> this image, the mass 30 signal starts out normally, rises and
> falls with mass 28 and 29. The mass 30 signal then spikes as
> mass 28 and 29 continue to fall.
> The fifth peak is the CO2 signal from the Acetanilide; I do
> realize that my changeover timing is off, and I plan to
> changeover about 10 or 15 seconds earlier than what is shown
> in this picture.
> If anyone has any ideas on what is causing this extremely
> high mass 30 peak, I would appreciate any knowledge and/or
> advice you can offer.
> Thanks for your help,
> Allison Burnett
> Master's Student
> Syracuse University