Isotopic composition analyzer

A method for the isotopic analysis of nitrogen in a sample comprising the sequential operation of the following steps:

• i) causing a carrier gas which does not comprise any nitrogen to flow through a heated catalytic reactor;
• ii) introducing said sample into said flow of carrier gas before it enters said catalytic reactor so that said sample is pyrolized in said reactor and
• a) any carbon present in said sample is converted to elemental carbon which is deposited in said reactor,
• b) any oxygen present in said sample is substantially completely converted to carbon monoxide by reaction with elemental carbon in said reactor,
• c) any hydrogen present in said sample is substantially completely converted to molecular hydrogen, and
• d) any nitrogen present in said sample is substantially completely converted to molecular nitrogen;
• iii) passing effluent from said catalytic reactor through a methanizer to reduce said carbon monoxide to methane;
• iv) conveying at least some of the gases emerging from said methanizer into a mass spectrometer;
• and
• v) determining the isotopic composition of the nitrogen by mass spectrometric measurements made on said molecular nitrogen.

A method for the isotopic analysis of nitrogen and/or oxygen in a sample comprising the sequential operation of the following steps:

• i) causing a carrier gas which does not comprise any nitrogen and/or oxygen to flow through a heated catalytic reactor, said reactor containing carbon maintained at about 1000.degree. C.;
• ii) introducing said sample into said flow of carrier gas before it enters said catalytic reactor so that said sample is pyrolized in said reactor and
• a) any carbon present in said sample is converted to elemental carbon which is deposited in said reactor,
• b) any oxygen present in said sample is substantially completely converted to carbon monoxide by reaction with elemental carbon in said reactor,
• c) any hydrogen present in said sample is substantially completely converted to molecular hydrogen, and
• d) any nitrogen present in said sample is substantially completely converted to molecular nitrogen;
• iii) passing at least some of the effluent from said catalytic reactor through a chromatographic column to temporally separate carbon monoxide and nitrogen;
• iv) conveying at least some of the gases emerging from said chromatopgraphic column into a mass spectrometer;
• and
• v) determining the isotopic composition of at least one said element selected from the group consisting of nitrogen and oxygen by mass spectrometric measurements made on said carbon monoxide or molecular nitrogen.

A method of determining the isotopic composition of at least one element of a sample, the said element being selected from carbon, nitrogen and oxygen, said method comprising the sequential operation of the following steps:

• i) causing a carrier gas which does not comprise any or said selected element to flow through a heated catalytic reactor, said reactor containing carbon and comprising a platinum/rhodium alloy catalyst maintained at about 1200.degree. C.;
• ii) introducing said sample into said flow of carrier gas before it enters said catalytic reactor so that said sample is pyrolyzed in said reactor and
• a) any carbon present in said sample is converted to elemental carbon which is deposited in said reactor,
• b) any oxygen present in said sample is substantially completely converted to carbon monoxide by reaction with elemental carbon in said reactor,
• c) any hydrogen present in said sample is substantially completely converted to molecular hydrogen, and
• d) any nitrogen present in said sample is substantially completely converted to molecular nitrogen;
• iii) conveying at least some of the gases emerging from said catalytic reactor into a mass spectrometer;
• and
• iv) determining the isotopic composition of at least one said element selected from the group consisting of oxygen, nitrogen and hydrogen by mass spectrometric measurements made on said carbon monoxide, molecular nitrogen or molecular hydrogen respectively.

A method of determining the isotopic composition of at least one element of a sample, the said element being selected from carbon, nitrogen and oxygen, said method comprising the sequential operation of the following steps:

• i) causing a carrier gas which does not comprise any of said selected element to flow through a heated catalytic reactor, said reactor containing carbon maintained at about 1000.degree. C.;
• ii) introducing said sample into said flow of carrier gas before it enters said catalytic reactor so that said sample is pyrolyzed in said reactor and
• a) any carbon present in said sample is converted to elemental carbon which is deposited in said reactor,
• b) any oxygen present in said sample is substantially completely converted to carbon monoxide by reaction with elemental carbon in said reactor,
• c) any hydrogen present in said sample is substantially completely converted to molecular hydrogen, and
• d) any nitrogen present in said sample is substantially completely converted to molecular nitrogen;
• iii) conveying at least some of the gases emerging from said catalytic reactor into a mass spectrometer;
• and
• iv) determining the isotopic composition of at least one said element selected from the group consisting of oxygen, nitrogen and hydrogen by mass spectrometric measurements made on said carbon monoxide, molecular nitrogen or molecular hydrogen respectively.