We present an efficient, easy-to-use chromatographic method to separate reactive and nonreactive sulfur compounds in crude oil for subsequent quantitative analysis and molecular characterization. Sulfur compounds in petroleum samples are separated by ligand exchange chromatography (LEC) on a silver-modified strong-cation exchange (SCX) solid-phase extraction (SPE) cartridge. LEC separation takes advantage of the bonding affinity of different sulfur types with silver-cations. The elution of a particular sulfur type (reactive or nonreactive) depends on the "strength" of the solvent used. One solvent mixture elutes nonreactive sulfur compounds (thiophenics and diaryl sulfides) into the first fraction. A second solvent mixture elutes reactive S-compounds (sulfides and disulfides) into the second fraction. A third reactive sulfur class (thiols) irreversibly reacts with the impregnated silver-ion to form silver thiolates that are insoluble in the solvent mixtures employed. The distribution of reactive and nonreactive sulfur in a sample can be determined by measurement of sulfur content in separated fractions. The isolated fractions are also well-suited for molecular characterization by a variety of techniques including gas-chromatography-based methods (e.g., GC or GC x GC-SCD, GC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), both of which are demonstrated herein.