In this paper, a fast, simple and new alternative method for determination of water content (moisture) in biodiesel using electrochemical impedance spectroscopy (EIS) is developed. The method is based on the sensitive variation of the charge transfer resistance (R) of the biodiesel medium in the presence of different quantities of water. To obtain an accurate analytical measurement, a pre-treatment based on a simple dilution by acetonitrile is employed. The two identical Pt electrodes are used in the measurement cell filled with sample solution. The experiment conditions are also optimized for the measurements. The obtained analytical linear curve between the water content and EIS impedance is the basis for the water content analysis in biodesiel fuel. The EIS method is then successfully applied to both real and certified samples, and the results confirm that the method is reliable with high sensitivity, precision and accuracy. The comparison of EIS method with the official standard method is also made through the Student test t, demonstrating that both methods are statistically consistent and similars. The validation of such an EIS method confirms that the method presented for the fist time in this paper can be succesessfully applied to determining the water content of biodiesel fuel.

No abstract

1IntroductionBiodiesel, mainly producedu sing basic liquid catalysts (KOH or NaOH)f or triglyceridest ransesterification [1,2] is one of the main biofuels used in the world, which can be mixed with petroleum diesel to form an alternative automobile fuel [3][4][5].Due to the biodiesel being one of the renewable fuels, the first reasonb ehindt he biofuels program is to reduce oil dependencyand increase the use of renewable,besides the warranty of increasing of energys ecurity.Biodiesel can be used in its pure form (B100) [6][7][8][9] or in many differentc oncentrations [10][11][12],b eing the most common, B20 (20 %b iodiesel, 80 %p etroleum diesel), B5 (5 %b iodiesel, 95% petroleum diesel) and B2 (2 % biodiesel, 98 %p etroleum diesel) [13].B 20 and lowerlevel blends usually do not require enginem odifications [14][15].B esides the positive environmental aspects, the presence of biodiesel in the blendsw ith diesel, could act as alubricity additive [12,13,16,17].Several alternativem ethodsf or quantitative determination of biodiesel contenti nd iesel-biodiesel blends have been reported in literature [18][19][20][21][22][23][24][25][26][27][28][29][30],s uch as x-ray spectroscopy [18],l iquid and gas chromatography [19][20][21], near infrared spectroscopy [22,23],f ouriert ransform mid-infrared spectroscopy (FT-IR) [25,26],u ltraviolet absorptions pectroscopy [27],f luorescence spectroscopy [30],a sw ell as electrochemical impedance spectroscopy (EIS) [31][32][33].Although some of these methodsare effective,m ajor drawbacks have been observed in the analysis.Theu se of electroanalyticalm ethods [34][35],i ncluding the method EIS [36-37]h as been as ubject of great interest in the last decade in many areas. Them ethod EIS, which uses the dielectric properties to measure the content of biodiesel, seems to be quite promising.Actually,t he application of EIS to study low conductivity media such as oil products,e thanol,a nd biodiesel have been reported in literature [10,11,37,38,39,40],a nd the high ohmic drop seemed to be not ac oncern [41,42]. One of the EIS advantages for biodiesel content measurements is its efficiency being able to obtain, in as ingle experiment, all informationa bout the solution, the interface and the electrodes urface,t hrough the measured parameters, such as resistance,c apacitance,a nd inductance, Abstract:T he blending ratio of biodiesel in petroleum diesel has become one of the most important parameters to ensuret he quality of diesel/biodieselb lend. This paper presents af ast and simple method based on electrochemical impedance spectroscopy to determinet he biodiesel contenti nd ieself uel. Differentf rom the methodr eported in the literature, using ap air of two identicals creen printed carbon pastee lectrodes,i nt he present work we used two electrodes made from 304 stainless steel with dimensions of 0.8 0.3 cm for the EIS measurements.I mproved results were obtained in terms of sensitivity,s tability of measurements,e lectrode reuse,a nd cost. In this procedure the charge transfer resista...

No abstract