Fuel Forensics Using ATR-FTIR Spectroscopy and Chemometric Approaches

As in most developed countries, the main petroleum products used for road transportation in India are gasoline and diesel fuel. Unfortunately, the adulteration of these products can be performed by the unscrupulous by using a variety of miscible substances, including (but not limited to) kerosene, turpentine, thinner, and ethanol. The Institute of Forensic Science and Criminology of Bundelkhand University (Jhansi, India) has used Fourier transform infrared spectroscopy (FT-IR) combined with principal component analysis (PCA) and partial least square regression (PLSR) to investigate adulteration in petroleum products and to design an adulterant profiling method. Spectroscopy spoke to the corresponding author of the resulting paper, Vijay Kumar Yadav, about their monitoring efforts.

How serious a problem is fuel adulteration? How does it affect the economy? How does it affect the environment?

This issue poses significant challenges with wide-ranging implications for the economy, ecology, and public health.

1. Economic Consequences: Adulterated fuel can cause significant harm to vehicle engines, resulting in increased maintenance expenses for vehicle owners and reduced lifespan of the vehicles.
2. Revenue Loss: Governments suffer significant revenue losses due to fuel adulteration, as contaminated fuels are often sold at lower rates outside of formal trade channels, thereby evading taxes. Market distortion occurs when suppliers of contaminated fuels gain an unfair edge over legitimate enterprises, disrupting market dynamics and creating an uneven playing field.
3. Rising operating costs: Escalating maintenance expenses and reduced fuel efficiency have resulted in higher operational expenditures for firms reliant on transportation.
4. Impacts on the Environment:

• Heightened Emissions: Unrefined or tainted gasoline typically leads to incomplete combustion, hence causing an escalation in the release of hazardous pollutants such as carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter.
• Air Quality Degradation: This refers to the deterioration of air quality caused by an increase in emissions, which has a negative impact on both human health and the environment.
• Soil and water contamination: This can occur when contaminated fuel is released during its handling and storage. This can lead to pollution of both soil and water systems, which can have negative effects on ecosystems and increase the likelihood of the contaminants entering the food chain.
• Climate change: This is mostly caused by the excessive release of greenhouse gases into the atmosphere due to the improper combustion of tainted fuel, which potentially increases global warming effects and various other negative consequences.

How is the fuel adulterated? Are there any adulterating agents that are better or worse than others?

Fuel adulteration is an illicit technique that involves mixing lower quality or substandard substances with fuel in order to increase its quantity and lower production costs. This behavior has the potential to result in substandard gasoline quality, which can cause damage to engines, negatively impact the environment, and have adverse effects on public health as a whole. This analysis examines the process of gasoline adulteration and several substances that cause contamination.

Common Adulterating Agents and Their Effects

Kerosene:

• How: Mixed with diesel and gasoline due to its lower price.
• Effects: Leads to incomplete combustion, increased smoke, higher particulate emissions, and potential damage to engine components like injectors and valves.

Solvents and Industrial Oils:

1. How: Blended with gasoline and diesel to increase volume.
2. Effects: Results in poor combustion, increased emissions, and potential fouling of engine parts.

Low-Grade Fuels:

1. How: Mixing lower-octane fuels with higher-octane fuels to sell at premium prices.
2. Effects: Results in engine knocking, reduced fuel efficiency, and potential engine damage.

Comparative Severity of Adulterating Agents

Kerosene: Their wide use increases the cost of engines and environment of engines due to the fact that they are commonly used impurities.

Solvents and Industrial Oils: They can cause a lot of pollution because they spoil engines badly.

Used Engine Oil – This is one of the worst impurities as it adds heavy metals and other contaminants into fuel which leads to long-term engine problems and environmental damage.

Low-Grade Fuels: These can lead to engine knocking and reduced efficiency but are generally less harmful than contaminants like used engine oil or industrial solvents.

What makes detection of the adulteration so difficult that spectroscopic analysis needs to be incorporated into the process?

Spectroscopic techniques offer a resolution to these difficulties by providing exceptional sensitivity, specificity, and expedited analysis capabilities. Here is an explanation of their functioning and the reasons behind their effectiveness—infrared spectroscopy is a technique that identifies and analyzes the unique vibrational patterns of chemical bonds, serving as a distinctive identifier for various compounds. The device has the capability to detect and measure adulterants, even at low levels, by identifying certain absorption bands. Spectroscopic analysis is crucial in detecting fuel adulteration due to the intricate and diverse nature of fuel compositions, as well as the requirement for precise and accurate detection. To summarize, spectroscopic analysis is a potent and flexible method for identifying fuel adulteration. It combines exceptional sensitivity and specificity with the ability to conduct quick and non-destructive tests. The ability of this asset to deliver precise, dependable, and uniform outcomes makes it an indispensable tool in guaranteeing the quality and authenticity of gasoline.

Why was attenuated total reflectance-Fourier transform infrared (ATR–FT-IR) spectroscopy your technique of choice in your analysis (1)?

ATR–FT-IR spectroscopy is a very effective and flexible method. The reasons for this include the generation of detailed molecular information, chemical fingerprinting, the utilization of non-destructive testing, and the minimal sample preparation and lower operational costs.

ATR–FT-IR spectroscopy is an excellent option for analyzing fuel adulteration. It is highly sensitive and specific, provides speedy results without causing damage, is versatile and easy to use, and is cost-effective. These benefits render it a sturdy and dependable instrument for ensuring the purity and authenticity of fuel in diverse environments.

Why did you select principal component analysis (PCA) and partial least square regression (PLSR) for your data analysis approaches?

PCA and PLSR are robust statistical methods commonly employed in chemometrics and data processing, specifically in intricate situations such as fuel adulteration detection. Data simplification, visualization, signal clarity enhancement, and efficient data handling are all aspects of complex data processing.

PCA and PLSR are selected for fuel adulteration investigation because they provide complimentary capabilities in reducing data dimensions, reducing signal noise, constructing predictive models, and managing complicated multivariate data. When used in combination, these techniques offer a robust foundation for precisely identifying and measuring fuel contaminants.

Briefly state your findings in this study.

The combination of ATR–FT-IR spectroscopy and chemometrics has demonstrated its efficacy as a straightforward, valuable, and easily understandable method for identifying and detecting adulteration in gasoline and diesel fuels. Both PCA and PLSR models are suitable for distinguishing various types of contaminated fuels based on spectroscopic data. The PCA models successfully classified samples based on the type of adulterant employed, achieving a variance of 98% for both diesel and gasoline fuels, respectively. These findings correlate what we have hypothesized.

Was there anything particularly unexpected that stands out from your perspective?

No, there wasn't anything particularly unexpected that stands out from my perspective.

Were there any limitations or challenges you encountered in your work?

No significant challenges were found in this work. One of the most significant challenges faced is the limited availability of standardized petroleum samples.

What best practices can you recommend in this type of analysis for both instrument parameters and data analysis?

Some recommended methods for both instrument parameters and data analysis include selecting the appropriate instrument, preparing the sample, calibrating and validating the instrument, assessing sensitivity and specificity, and considering environmental conditions.

Can you please summarize the feedback that you have received from others regarding this work?

The research work on gasoline adulteration analysis utilizing ATR–FT-IR and chemometrics is a praiseworthy contribution to the discipline. The combination of ATR–FT-IR spectroscopy and sophisticated chemometric techniques is highly unique, providing a reliable method for identifying and measuring adulterants in fuel samples. The methodology is thoroughly described, ensuring the ability to replicate and understand the experimental processes with precision. The findings are presented accurately, backed by thorough statistical analysis, and the discussion effectively connects these results to previous literature, emphasizing the importance of the study. Nevertheless, the work would be enhanced by a more thorough examination of the study's constraints and the tangible ramifications of the results for practical use in real-life scenarios. Furthermore, incorporating new progressions in the literature review would offer a more up-to-date framework for the study. In general, the study exhibits a well-organized structure and articulate writing, demonstrating evident promise for practical implementation in the field of fuel quality monitoring.

What are the next steps in this research and are you planning to be involved in improving this technology?

Subsequent stages of this research will focus on improving the ATR–FT-IR and chemometric techniques to increase the accuracy and precision in identifying a broader spectrum of contaminants at lower levels of concentration. This involves the advancement of chemometric models and algorithms to enhance the accuracy of data analysis and the investigation of incorporating additional complementary analytical techniques to offer a more thorough evaluation. Field trials and real-world application testing are essential for validating laboratory findings and adapting technologies for practical usage in the fuel sector. Furthermore, it will be crucial to examine the economic and operational viability of implementing this technology on a significant scale. I am enthusiastic about participating in these breakthroughs, making contributions to both the technical enhancements and the larger implementation methods to ensure that this technology can effectively prevent gasoline adulteration in many scenarios.

References

(1) Babu, B. K.; Manohar Yadav, M.; Singh, S.; Kumar Yadav, V. Fuel Forensics: Recent Advancements in Profiling of Adulterated Fuels by ATR-FTIR Spectroscopy and Chemometric Approaches. Spectrochim. Acta A Mol. Biomol. Spectrosc. 2024, 312, DOI: 10.1016/j.saa.2024.124049

Vijay Kumar Yadav is currently providing his services to the Dr. A.P.J. Abdul Kalam Institute of Forensic Science and Criminology, Bundelkhand University, Jhansi, Uttar Pradesh, as an Assistant Professor. He received his Master’s degree and PhD at Bundelkhand University, Jhansi, and joined the faculty at Bundelkhand University, Jhansi, where he has been teaching since 2011. From 2018 to 2021, he served as Coordinator/Head of Department. He has more than 13 years’ experience teaching UG and PG Students of Forensic Science at Bundelkhand University. He has been a member and convener of the Board of Studies Committee on Forensic Science Subjects since 2015. He has been a member of the University Proctorial Board as an assistant proctor. He has actively participated in various extracurricular activities organized by Bundelkhand University, Jhansi. During his 13-year journey, he has published more than 30 research papers and several book chapters in different journals of national and international repute. Yadav has supervised the dissertations of more than 90 postgraduate students. In addition to this, two research scholars are currently pursuing their doctoral theses under his supervision. He has organized various national and international conferences, seminars, and workshops at Bundelkhand University, Jhansi. He has visited or been invited to various forensic science laboratories and forensic science institutions for training and research, talks, and lectures. Specifically, he worked in the field of forensic chemistry and material science, with research interests focused on different aspects of adulteration in materials and arson analysis. Yadav is associated with different universities as a member of the Board of Studies Committee and examiner panel. He is a prestigious life time member of the Indian Science Congress Society. He is also serving as a reviewer for various national and international journals. Photo courtesy of Vijay Kumar Yadav.