Toward the Development of Raman Spectroscopy as a Nonperturbative Online Monitoring Tool for Gasoline Adulteration (original) (raw)

2013, Analytical Chemistry

There is a critical need for a real-time, nonperturbative probe for monitoring the adulteration of automotive gasoline. Running on adulterated fuel leads to a substantive increase in air pollution, because of increased tailpipe emissions of harmful pollutants, as well as a reduction in engine performance. Consequently, both classification of the gasoline type and quantification of the adulteration content are of great significance for quality control. Gasoline adulteration detection is currently carried out in the laboratory with gas chromatography, which is time-consuming and costly. Here, we propose the application of Raman spectroscopic measurements for on-site rapid detection of gasoline adulteration. In this proof-of-principle report, we demonstrate the effectiveness of Raman spectra, in conjunction with multivariate analysis methods, in classifying the base oil types and simultaneously detecting the adulteration content in a wide range of commercial gasoline mixtures, both in their native states and spiked with different adulterants. In particular, we show that Raman spectra acquired with an inexpensive noncooled detector provides adequate specificity to clearly discriminate between the gasoline samples and simultaneously characterize the specific adulterant content with a limit of detection below 5%. Our promising results in this study illustrate, for the first time, the capability and the potential of Raman spectroscopy, together with multivariate analysis, as a low-cost, powerful tool for on-site rapid detection of gasoline adulteration and opens substantive avenues for applications in related fields of quality control in the oil industry. A utomotive gasoline or petrol is a complex organic compound, composed of volatile liquid hydrocarbons and a variety of additives, obtained through fractional distillation of crude petroleum oil. 1 The octane rating, which is also known as the octane number, is a standard measure of the performance of the automotive fuel, where, typically, gasoline with a higher octane rating is used in high-compression engines that have higher performance. Because of the financial incentives arising from differential taxes, automotive gasoline and diesel is often adulterated to maximize profits. 2−4 In particular, it has been reported that a diverse array of chemicals, ranging from kerosene and industrial solvents to used lubricants, are blended with the gasoline. 4 In addition, the adulteration of gasoline could also involve the blending of higher-grade gasoline with a lower-grade one. In order to avoid detection, the added adulterant has been observed to be typically limited to within 10%−20% by volume. 3 Clearly, this represents a particularly undesirable situation, as automotive engines are designed and manufactured to run on a specified grade of fuel. Therefore, running the same engines on adulterated fuel is likely to increase the air pollution, because of increased tailpipe emissions of harmful pollutants (including hydrocarbons, carbon monoxide, and particulate matter) and