Multicommutation Fourier transform infrared determination of benzene in gasoline

A fully mechanized method to determine benzene in motor gasolines has been developed based on the use of Fourier transform infrared spectroscopy (FT-IR) and multicommutation. The flow network comprised a set of three-way solenoid valves and was controlled by means of a microcomputer furnished with an electronic interface and running by a software written in QUICK BASIC 4.5. The flow network and control software were designed to implement the multicommutation approach providing facilities to handle sample and reagent solutions, so that, sample dilution, external calibration and standard addition could be easily performed online. The method permits the direct determination of benzene without any pre-treatment of samples, with a limit of detection of 0.004% (v/v) and a variation coefficient of 1.2% (for 10 independent analysis of a gasoline sample containing 3% (v/v) benzene). Advantageous features of the method were a linear response ranging until to 3.75% (v/v), a solvent consumption of 1.2 ml per determination and an analytical throughput of 81 samples per hour. So, the described method is a fast and sustainable alternative to the previous methods for benzene determination in gasolines.