Probe-based spectrophotometric quantification of petrol-ethanol fuel blends for field-able applications

•Easy & precise quantification of ethanol-petrol blends using probe-based absorption spectroscopy.•Selection and introduction of probing molecule in a simple and legitimate manner using a biodegradable hydrogel.•Generalized method for the accurate quantification of blends with fuel sample of different origin.•Possibility of devising a low-cost, portable, layman-friendly and fieldable tool for fuel blend composition.•Two modes of quantification: Hyperchromic enhancement monitoring and Sample-independent ratiometric analysis using band pass excitation. Blending a cleaner, less expensive fuel like ethanol to petrol is a low-hanging fruit to address fuel crisis. However, blending bioethanol beyond the permissible limit can eventually corrode engine parts and cause fuel tank swelling. As a result, ensuring the quality of fuel blends is a critical step for consumers. We propose an inexpensive method for the precise quantification of fuel blend composition using a probing technique that exploits the structural switching and consequent change in transition probability of the probe molecule in polar and non-polar media. The UV-visible absorption spectrum of the probe is capable of exhibiting a hyperchromic shift with increasing ethanol composition in the blend. Two calibration models have been constructed based on the data - the hyperchromic shift-based model yielded excellent analytical figures of merit with LOD, LOQ and RMSEP values of 0.02,0.08 and 0.23%, respectively. Calibration using ratiometric analysis showed LOD, LOQ and RMSEP values of 0.01, 0.04 and 0.13%, respectively. The approach provided a simpler and sample-independent method that can be easily integrated into a LED-spectrophotometer for commercial and in-situ applications. A novel, biodegradable- hydrogel based probe delivery is illustrated and optimized. An analysis of real samples has been carried out using our method and the results discussed. [Display omitted] A portable LED spectrophotometer- 'ethano-meter' for quantifying ethanol in fuel blends using an external probe molecule is proposed for in-situ fuel quality control.