Nano-sized polyaniline (50–150 nm) has been prepared by polymerization of aniline on the surface of the commercial polyester fiber. A method for determination of adulteration in lemon juice samples was developed. Solid-phase microextraction (SPME) by polyester-polyaniline fiber to extract volatile organic compounds (VOCs) and analysis of gas chromatography (GC) profile were used. The effects of industrial lemon juice (ILJ) percent, organic lemon juice (OLJ) percent, and storage time of lemon juice as tree variable factors on the gas