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A method has been developed to determine the boiling point distribution of sulfur compounds in light cycle oils (LCO'S). The method chosen for this analysis was GC with a flame photometric detector (FPD) and pyrolyzer. Tests were carried out to evaluate the recovery efficiency, repeatability, and accuracy of the method. Repeatabilities within 2% were obtained. The recovery of benzothiophenes and dibenzothiophenes was close to 100%; this was important because these are the major sulfur components in LCO's. No hydrocarbon or solvent interferences were observed Gith the use of the pyrolyzer, even for a 95% solvent level. Comparison with results from other techniques showed that the method accurately determined the levels of sulfur compounds in the LCO boiling point range.

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not with cyclohexane. From these results, the desired properties of suitable secondary solvent seem to be the following: (i) the secondary solvent should have good affinity for the solutes of interest; (ii) a solvent having no affinity for the solutes is also effective if the latter have a good affinity for stationary phase.The secondary solvent technique is a very useful method for overcoming peak distortion. It is applicable to polar solutions and even for water-containing solutions.