Dual channel System for CN-S-H/D-O isotope analyses

For the isotope analysis we design special analyser. For this application it is important that you have a diffusion free system and a very low blank for the autosampler. This results in very low blank and background in the IRMS.

The analysis for CN-S is done through a combustion and complete oxidation of the sample. By the exothermal oxidation of the tin cap, we reach up to 1800°C at the sample. After the reduction of NOx and SO3 the reaction gases are separated on a gaschromatographic column and passed to the mass spectrometer.

The analysis of H/D and oxygen is carried out in a high temperature pyrolysis system. The sample, weighed in silver caps is inserted into the pyrolysis reactor by the automated sampler. Here the hydrogen and oxygen of the sample reacts with the carbon reactor filling at 1450° - 1500° C to form H2 and CO. The gases are separated on a chromatographic column and passed to the IRMS.
The system can be constructed as a dual channel analyser enabling CN-S or oxygen and hydrogen analysis without reconstruction.

Layout for CN and HT-oxygen

For the pyrolysis the temperature is very important. For organic oxygen there is no problem, but to convert inorganic oxygen in CO the temperature must be more than 1450°C. For hydrogen from organic samples you can have problems with the formation of methane at lower temperature. ( see also application note CHN 012 )

NEW:
Our new reactor layout guaranteed that the glassic carbon tube is centre in the ceramic tube, so that there is no contact of the tubes. This is important to have no reaction of the ceramic and carbon so that there is a low background of CO. On the other side there is no contact of the reaction gases to any material witch contain oxygen, so that there is no exchange of isotopes. The typical standard deviations are 1 ‰ for D/H and
0.2 ‰ for oxygen.
For Water analysis it is possible to inject the sample directly with an automatic liquid sampler into the reactor.