Estimation of nitrogen-to-carbon ratios of organics and carbon materials at the submicrometer scale

Precisely estimating nitrogen-to-carbon (N/C) ratios of carbonaceous materials at the submicrometer scale is a challenge in both natural and material sciences. Following recent attempts reported in the literature, the present paper discusses two methods of quantification of the N/C ratio of organics and carbon materials at the submicrometer scale using nanoscale secondary ion mass spectrometry (NanoSIMS) and X-ray absorption spectroscopy (XAS). The present contribution highlights the need to use at least two standards to build a calibration line in order to precisely and accurately (±0.009–95% confidence level) estimate N/C values of unknown carbon samples using NanoSIMS. As shown here using a set of reference compounds, STXM-based XAS allows directly estimating N/C ratios of organics without using any standard with errors as low as 0.007.