Quantification of Lambda (?) in multi-elemental compound-specific isotope analysis

In multi-elemental compound-specific isotope analysis the lambda (?) value expresses shift of one element versus a second element. dual-isotope plots, slope regression lines typical reveals footprint underlying effects allowing to distinguish degradation pathways an organic contaminant molecule in environment. While different conventions and fitting procedures are used literature determine ?, it remains unclear how they affect magnitude ?. Here we generate synthetic data for benzene ?2H ?13C with two enrichment factors ?H ?C using Rayleigh equation examine linear yield distinct Fitting error-free set graph plotting overestimates ? by 0.225%??H/?C, meaning that if ?H/?Cis larger than 22, is overestimated more 5%. The correct requires natural logarithmic transformation data. Using this transformation, ordinary (OLR), reduced major-axis (RMA) York methods find even large ?H/?C. dataset random errors let same conclusion positioned suitability each method. We conclude non-transformed ? values should be discontinued. validity most previous not compromised, although previously obtained ?H/?C could corrected our error estimation improve comparison.