ConFlo III - An interface for high precision delta C-13 and delta N-15 analysis with an extended dynamic range

A newly developed interface coupling a CHN combustion device (elemental ana lyser 'EA') to an isotope ratio mass spectrometer is described and evaluate d. The purpose of the device is to extend the dynamic range of delta(13)C a nd delta(15)N analysis from less than 2 orders of magnitude to more than 3 orders of magnitude. Carbon isotope ratio measurements of atropine as a mod el compound have been performed analysing between 1 mu g to 5 mg C with acc eptable to excellent precision (0.6 to 0.06 parts per thousand, delta-notat ion). The correction due to the blank signal is critical for sample amounts smaller than 4 mu g C. The maximum sample weight is determined by the comb ustion capacity of the EA, Larger sample amounts are measured using dilutio n of a small part of the EA effluent with helium. The dilution mechanism wo rks virtually free of isotope fractionation, Copyright (C) 1999 John Wiley & Sons, Ltd.