Many laboratories routinely analyze plant, animal and soil samples with elemental analyzers coupled to isotope ratio mass spectrometers, obtaining rapid results for nitrogen (%N, d15N) and carbon (%C, d13C) from the same sample. The coupled N and C measurements are possible because of a gas chromatography (GC) separation of N2 and CO2 gases produced in elemental analysis. Adding a second GC column allows additional measurement of sulfur (%S, d34S) from the same sample, so that combined N, C and S information is obtained routinely. Samples are 1-15?mg, and replicates generally differ by less than 0.1頦or d15N, d13C or d34S. An example application shows that the N, C, and S measurement system allows a three-dimensional view of element dynamics in estuarine systems that are undergoing pollution inputs from upstream watersheds. Extension of these GC principles should allow coupled H, C, N, and S isotope measurements in future work. Copyright 頲007 John Wiley & Sons, Ltd.