This paper describes a method for the determination of carbon content of all grades of steel, utilizing a modern direct reading emission spectrometer and a single calibration curve. The normal errors present when applying steels such as Hadfield's manganese steel and chromium bearing stainless steels to a curve prepared from plain carbon low alloy standard, were investigated and found to be entirely dependent upon the manganese and chromium contents of the sample. The coefficient of variation, after correction for manganese and chromium, was found to be 2% at the 2.0% carbon level increasing to 3.7% at the 0.030% carbon level in extra low carbon stainless steels.
Kelvin A. Clarke, "Determination of Carbon in Steels Using a Direct Reading Spectrometer and a Single Calibration Curve," Appl. Spectrosc. 24, 229-234 (1970)