Development of a cobalt(II) phthalocyanine- MWCNT modified carbon paste electrode for the detection of polyunsaturated fatty acids

In this work the development of an electrochemical sensor for the determination of polyunsaturated fatty acids (PUFAs), in particular linoleic acid, in commercially available safflower oil as complex matrix is described. The sensor consists of a carbon paste electrode with cobalt(II) phthalocyanine, Co(II)Pc, as mediator and multiwalled carbon-nanotubes (MWCNT) as nanomaterial. As carrier medium a sodium borate buffer (0.1 M, pH 9) was used. PUFAs were detected at a working voltage of 0.35-0.45 V (vs. Ag/AgCl). The sensor development was carried out in a batch system with differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Sensor specification was tested by using various fatty acids (stearic acid, oleic acid, linoleic acid, linolenic acid and arachidonic acid) as well as esterified fatty acids, resulting in a specific applicability towards PUFAs, especially linoleic acid (LAH). The optimized sensor was applied in a flow injection analysis system (FIA) for the analysis of PUFAs in complex matrix. Linoleic acid was used as standard substrate to determine the analytical parameters. The linearity ranges between 7.5 and 200 μg mL^-1 LAH, while the limit of detection was determined to be 2.5 μg mL^-1 and the limit of quantification is approximately 7.5 μg mL^-1 LAH. The LAH content was successfully detected in commercially available safflower oil via standard addition method and the results could be confirmed by a reference method. The PUFA content was calculated as LAH-equivalent.