Extraction-free techniques for sensitive detection of a petroleum marker on a paper-based platform

Abstract

Fuel adulteration and cross-contamination lead to low-quality fuel products and loss of taxes. It is essential to develop methods of marking, identifying and monitoring tax classification of petroleum products in the market. In this work, a method for sensitive and fast detection of gasoline marker using paper-based platform and a smartphone camera detection are developed. A common dye, phenolphthalein (PhP), is used as a colorless dye marker in commercial gasoline. The color was developed by the interaction of PhP with NaOH on filter paper strips and evaluated by CMYK color systems. The newly developed counter-flowing technique, in which a gasoline sample containing PhP and NaOH solution are allowed to travel on a filter paper strip from the opposite end, gives the naked eye detection of PhP as low as 1 ppm with the limit of detection for a smartphone camera of 0.31 ppm. The high sensitivity is attributed to the preconcentration derived from accumulation of PhP at the immiscible liquid interface. The counter-flowing method can thus be a new facile analytical technique for enhancing chemical detection sensitivity.