A true boiling point gas liquid Chromatograph (GLC) has been designed to measure simply and conveniently GLC data for all types of petroleum streams, including crude oils and residual fuels which contain considerable portions of high-boiling materials. The instrument generates simultaneous carbon and sulfur boiling point profiles up to 538°C (C42). A quantitative measure of the nonvolatile organic portion of the sample is achieved by backflushing and combusting the material remaining in the inlet. Thus, identification of oil pollution samples is facilitated by obtaining data on the carbon and sulfur distribution and the amount of residue in a single, rapid analysis. Under certain circumstances, the total recovery capability also permits the extent of weathering of oil pollution samples to be determined directly from the chromatographic results.