Photothermal detection of adulterants in automotive fuels

In this paper, we describe a new, simple, and fast photothermal method for detecting the presence of adulterants in commercial gasolines. The method consists essentially of measuring the time evolution of the gasoline vapor in an originarily air-filled closed cell using a pyroelectric sensor. The transient photothermal signal amplitude data fitting yields two parameters, namely, a saturation signal amplitude and the characteristic time for approaching saturation. From the values, two figures of merit are defined. The method was tested with a universe of 210 commercial samples collected in different gas stations. It is shown that the proposed method has an uncertainty of 5.7%. This good accuracy, together with its simplicity and fast response, may render it useful for developing a portable device for fast checking in field analysis.