Detection of motor gasoline adulteration by preliminary examination and FTIR spectroscopy

Fuel adulteration poses significant economic, environmental, and forensic challenges, particularly in developing countries. This study investigates motor gasoline adulteration using a tiered analytical approach combining preliminary screening tests with Fourier Transform Infrared (FTIR) spectroscopy. Thirty commercial gasoline samples (87 octane) were collected from major retail fuel stations across Kerala, India. Initial qualitative assessments included visual colour inspection and a filter paper spot test to identify the presence of high-boiling adulterants. Confirmatory analysis was performed using ATR-FTIR spectroscopy to obtain molecular fingerprints and detect compositional anomalies relative to certified reference gasoline. Preliminary tests indicated potential adulteration in several samples; however, FTIR spectroscopy conclusively identified six samples showing missing characteristic gasoline peaks and the appearance of extraneous bands associated with solvents or oxygenated compounds. The results demonstrate that while simple field tests are useful for rapid screening, they lack specificity. The integrated use of preliminary examinations and FTIR spectroscopy provides a reliable, rapid, and practical methodology for forensic fuel quality assessment and regulatory enforcement.