¹⁵N, ¹³C-On-line Measurements with an Elemental Analyser (Carlo Erba, NA 1500), a Modified Trapping Box and a Gas Isotope Mass Spectrometer (Finnigan, MAT 251)

Abstract

An on-line method for the determination of ¹⁵N and ¹³C with a gas isotope mass spectrometer (Finnigan, MAT 251) was developed to improve the sensitivity and to reduce measurements time and the cost of the sample analysis. For this purpose an elemental analyser (Carlo Erba, NA 1500) was coupled to the mass spectrometer using parts of the capillary system of a trapping box (Finnigan, type CN). For the determination of samples with natural concentrations of ¹⁵N and ¹³C the uncertainty of the delta value is less than 0.2 δ‰. The detection limit is in the order of 10 μg (total N or total C) and 7 samples can be analysed per hour.

Key Words:

• Carbon 13
• elemental analyser
• mass spectrometry
• nitrogen 15
• on-line measurement