SPME–GC determination of methanol as a hydrate inhibitor in crude oil

This work focused on the quantitation of methanol as a hydrate inhibitor in the crude oil. The novelty is microextraction of a polar compound from a complex non-polar matrix and selection of proper fiber with maximum selectivity, loading percent, and lifetime. This approach not only does not require specific instrumentation, such as multiple columns, and selective detectors, but also has eliminated the use of organic solvent and avoids the insertion of water inside the GC columns. The objective is optimization of extraction conditions, GC adjustments and data processing. Experiments were conducted on the real sample of Iranian offshore crude oil by a carboxen/PDMS fiber via a GC equipped with a cross-linked polyethylene glycol column and FID. The results revealed that this fiber adsorbed the alcohols among other light non-polar compounds of crude oil. Moreover, the interference effects of ethanol were solved by proper selection of thermal program. The LOD, LOQ and linear range of this approach were determined to be 3.9, 12.9 and 14–229 mg L−1 for methanol, respectively. Moreover, the sensitivity was 30 area-counts per mg L−1. Using the standard calibration and the standard addition methods, the relative errors of 1.6–7.2 and 5.3–14.0% were determined, respectively.