Determination of Lemon Juice Adulteration by Analysis of Gas Chromatography Profile of Volatile Organic Compounds Extracted with Nano-Sized Polyester-Polyaniline Fiber Mohammad Alizadeh 1 & Sajad Pirsa 1 & Nasrin Faraji 1 Received: 6 September 2016 /Accepted: 6 December 2016 # Springer Science+Business Media New York 2016 Abstract Nano-sized polyaniline (50–150 nm) has been pre- pared by polymerization of aniline on the surface of the com- mercial polyester fiber. A method for determination of adul- teration in lemon juice samples was developed. Solid-phase microextraction (SPME) by polyester-polyaniline fiber to ex- tract volatile organic compounds (VOCs) and analysis of gas chromatography (GC) profile were used. The effects of indus- trial lemon juice (ILJ) percent, organic lemon juice (OLJ) percent, and storage time of lemon juice as tree variable fac- tors on the gas chromatography profile were studied. D- optimal combined design (DOCD) was applied to design the experiments that study the gas chromatography profile. For this purpose, the recorded chromatograms of VOCs were di- vided into four-time sections (0–5, 5–10, 10–15, and 15– 20 min) and the peak number, total peak height, and total peak area in the four divided time sections were analyzed. The results were analyzed, and statistical test of correlation and linear regression was used. Results showed that there is good relation between industrial lemon juice percent, organic lemon juice percent, and storage time and peak characters (peak numbers, total peak height, and total peak area) in the divided time sections of each chromatogram. So, the presented meth- od is a good method to find adulteration in organic lemon juice by gas chromatography profile analysis. Keywords Lemon juice . Adulteration . Polyaniline . Nano-sized . Volatile compound . Gas chromatography profile Introduction For many years, polymers containing conjugated p- electron systems such as polypyrrole, polythiophene, and polyaniline have been well known. Polyaniline (PANI) attracted considerable attention because of its good envi- ronmental stability and high application potentials (Fabrizio et al. 1992; Cooper and Hall 1993; Ting et al. 1994). It can be obtained by chemical or electrochemical polymerization of aniline in the form of powder or a film. In situ chemical polymerization of aniline and pyrrole on the surface of textiles (nylon6 or 66, poly(ethylene tere- phthalate) (PET), and quartz) in aqueous solution was reported. Such conducting composites showed high flexi- bility and strength and many potential applications, such as absorbent, filtering system, the dissipation of electro- static charge, heating elements, and conducting materials (Ansari 2006; Bhadra and Khastgir 2008; Yang et al. 2007). Solid-phase microextraction (SPME) is a solid- phase extraction sampling technique that involves the use of a fiber coated with an extracting phase, which can be a solid (sorbent)-like polyaniline, which extracts different kinds of analytes (volatile or non-volatile or in- cluding both of them) from different kinds of media, which can be in liquid or gas phase (Jordan et al. 2001; Jia et al. 1988; Shaw and Wilson 1982; Steffen and Pawliszyn 1996; Kovats 1958; Yang and Peppard 1994). The quantity of analyte extracted by the fiber is propor- tional to its concentration in the sample as long as equi- librium is reached or, in the case of short time pre-equi- librium, with the help of convection or agitation. The analysis of volatile organic compounds (VOCs) using SPME coupled with headspace has received attention from many researchers. In headspace SPME (HS-SPME) analyses, a fiber is placed in the headspace above an * Mohammad Alizadeh m.alizadeh@urmia.ac.ir 1 Department of Food Science and Technology Faculty of Agriculture, Urmia University, P. O. Box, Urmia 5756151818, Iran Food Anal. Methods DOI 10.1007/s12161-016-0747-4