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  Thanks McKay for your suggestion.


Bithika Das

Research scholar

IIT Kharagpur

INDIA

On Tue, Apr 4, 2017 at 10:02 PM, Jen McKay <[log in to unmask]>
wrote:

> Hello Bithika,
>
> When we think our samples are going to be sulfur-rich (i.e., sediments and
> some biological materials) we add a small bit of Ni wool to the bottom of
> our quartz insert sandwiching the wool between two pieces of quartz wool.
> I had to do this because the sulfur was causing the formation of
> micro-fractures in our reaction column.
>
> Bye for now,
> Jennifer
>
>
> Jennifer McKay
> Assistant Professor (Senior Research)
> Stable Isotope Lab Manager
> CEOAS, Oregon State University
> Corvallis, Oregon 97331
> 541-737-4054
>
> On Apr 4, 2017, at 12:55 AM, bithika das <[log in to unmask]
> <[log in to unmask]>> wrote:
>
> Hello Isogeochem Members
>
>
> This mail is regarding a unique problem (to us possibly!), we are
> experiencing in our bulk organic matter δ13C measurements. Presently, we
> are analyzing rock samples (Old Oligocene-Miocene marine gray shale) in
> Flash EA 2000. Analytical conditions are as follows: Carrier flow: 120
> ml/min, Reference flow: 80-100 ml/min, Reactor temperature: 1020 °C, Oven
> temperature: 80 °C. EA 2000 is attached with the DeltaV through a ConFlo IV
> interface (Dilution 33%). Although ~50 % of the samples are with correct
> chromatograms (no problem detected), rest are creating some unique problem.
> The clean samples burn perfectly with no peak widening (i.e., for a ~5V
> peak we are expecting ~50-55 second peak width, when end slope is set at
> 4mv/sec). In agreement, both IAEA-C3 and NBS-22 are showing a peak width of
> ~48 second with the same instrumental setup.
>
>
> However, problematic samples showing peak widening (~70 second) and
> followed by an interesting hump (if we really call it) producing peak
> overlap and non-reproducible delta values. Just after the actual CO2 peak
> from the sample (identified by retention time) the 46 beam current
> increases rapidly without much change in 44 and 45 currents. Since, we
> don’t detect peak unless 44 beam-current is more than 50mV, this unique
> hump is never detected as peaks. The shape of this following peak is more
> like a plateau (broad with >300 sec peak width if we try to detect it). We
> suspected that this is coming from some Sulfur bearing organic matter or
> elemental Sulfur. We checked it by taking a background scan (intensity vs.
> magnetic steps) just after the measurement (showing high SO2 compared to
> clean run or if we take the scan just after the reactor cleaning).
>
>
> We wonder whether any of you have come across such a problem. If, so
> please suggest how to get rid of this peak, if possible.
>
>
>  Thanking you in advance
>
> With best regards
>
>
> Bithika Das
>
> Research scholar
>
> IIT Kharagpur
>
> INDIA
>
>
>