High-temperature elemental analysis and pyrolysis techniques for stable isotope analysis.

A universal method for pyrolysis and elemental analysis, suitable for the online determination of deuterium, carbon, nitrogen and oxygen isotopes for organic and inorganic substances, is presented. The samples are pyrolytically decomposed in a high-temperature pyrolysis (HTP) system, at a temperature exceeding 1400 degrees C, in the presence of reactive carbon. The method is suitable for the analysis of stable isotope ratios from hydrogen, carbon, nitrogen and oxygen. The instrumentation and experimental procedure are simple and cost-effective. The reproducibility of the delta values for D/H is better than 3 per thousand, and for (18)O, (13)C (organic) and (15)N (inorganic) it is approximately 0.2 per thousand. The HTP system is suitable for solid and liquid samples and can use an autosampler for the samples. Results are presented for the isotopic composition of international reference materials and selected laboratory reference materials, which demonstrate the precision and accuracy of the method. Possible problems in the measurement of nitrates and their solutions are particularly discussed. The analyses of oxygen isotopes in selected geological samples (carbonates, silicate, biotite) are demonstrated. Copyright 2003 John Wiley & Sons, Ltd.