This method is for determining primary, secondary and tertiary mercaptans (thiols) in kerosines up to several thousand mass-ppm, based on the procedure previously suggested by E. Rafii, et al. (1,2). The lower limit of detection by 119Sn {H} decoupled, refocused Insensitive Nucleus Enhancement by Polarization Transfer (INEPT) Nuclear Magnetic Resonance (NMR) spectroscopy without preconcentration is 40 mass-ppm per mercaptan type in the kerosine. Lower concentrations can be determined using a specified distillation procedure. The only known interferences are thiophenols and branched alcohols, such as isopropyl and butyl alcohols (see NOTE). The method relies upon the quantitative preparation of soluble tri-n-butyl tin derivatives of all of the thiols present.