Liquid chromatographic identification of oils by separation of the methanol extractable fraction

Abstract

A liquid chromatographic oil spill identification technique employing dual ultraviolet detection was developed. The methanol-extractable fraction was removed from the oil samples and separated on a reverse-phase column using a water/methanol gradient. Ratios of the peak heights of two closely eluting bands (..cap alpha.. = 1.01; detector lambda = 254 nm), common to all oils studied, were reproducible to within +-3.0 percent. This ratio was used for screening improbable oil spill source samples. A series of intra-chromatographic peak-height ratios was then used to define a ''fingerprint'' region (detector lambda = 210 nm). The spill chromatogram was used as a standard to which all suspects were compared for matching purposes. This matching technique showed that, as an oil weathered, the standard error of the standard deviations between any two chromatograms (weathered and unweathered) increased proportionately to exposure time. This permitted the calculation of an estimated time of spillage (+-8 h) based on the linear increase of the standard error with time, for nine of the eleven oils tested.