ORIGINAL PAPER Morphological characterization of ex situ prepared bismuth film electrodes and their application in electroanalytical determination of the biomolecules Nives Vladislavić 1 & Marijo Buzuk 1 & Slobodan Brinić 1 & Maša Buljac 2 & Marija Bralić 2 Received: 4 March 2016 /Revised: 26 April 2016 /Accepted: 29 April 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract A study on the preparation and characterization of the potentiostatically prepared bismuth films (BiFs), in order to obtain satisfactory electroanalytical tool, is presented. BiFs formed on glassy carbon were characterized by electrochem- ical impedance spectroscopy (EIS) and scanning electron mi- croscopy (SEM). The dependence of the BiFs properties upon electrolytes composition and electrochemical parameters are discussed and diagnostic criteria that allow estimation of the BiF morphology are proposed. Analytical performance data of the formed BiF electrodes were obtained by their application to the determination of glutathione (GSH) and folic acid (FA) using square-wave cathodic stripping voltammetry. The de- pendence of the analytical performance of the formed BiFs on their specific surface areas, along with their different mor- phology, is discussed. Adequate method and parameters for the electrochemical formation of optimal BiF, in order to ful- fill the analytical requirements, are proposed. The best analyt- ical performance was obtained with films formed from acetic buffer solution spiked with EDTA, as a consequence of the improved surface coverage and most arranged homogenous structure of the film. This electrode displays a linear response range toward GSH with estimated detection limit of 0.005 μM and sensitivity of 3.28 μA μM −1 for linear range of 0.01 to 0.1 μM. Also, the utilization of the BiF electrode for the determination of FA was demonstrated by direct electroreduction of FA. Keywords Bismuth film electrodes . Film morphology . Biomolecule . Electroanalytical Introduction In the last 15 years, bismuth has become an attractive and promising material for electroanalytical application due to its low toxicity and good operating cathodic potentials (thus ex- cluding oxygen interference and hydrogen evolution over electroanalytical potential window). The electrodeposition of bismuth, on various substrates, has become the most com- monly used electrode construction method, owing to the prep- aration protocol simplicity and electroanalytical performance of the electrodes prepared by this method (when compared to the mercury electrodes). However, the electroanalytical prop- erties of bismuth film (BiF) are strongly influenced by its nature (structure, morphology, adherence, etc.) and this rela- tionship has been described by several authors. A significantly improved bismuth film was formed from the acid solution of Bi(III), in the presence of bromide ions. By using this method, Krolicka et al. [1] formed an adhesive bismuth film on GC, characterized with large, lumpy, perpendicular crystallites, which showed good performance in the determination of Co 2+ . Moreover, in the presence of the same anion, Hutton et al. [2] prepared a uniformly and thoroughly coated bismuth film on a carbon fiber surface. Authors demonstrated a high long-term functional stability, as morphology and structure of the bismuth film remained unchanged even after 40 consecu- tive determinations of Co 2+ . Other additives were also used to obtain satisfactory Bi films. Therefore, Nunes et al. [3] per- formed the bismuth electrodeposition from hydrochloric acid, * Marijo Buzuk buzuk@ktf-split.hr 1 Department of General and Inorganic Chemistry, Faculty of Chemistry and Technology, University of Split, R. Boškovića 35, 21000 Split, Croatia 2 Department of Environmental Chemistry, Faculty of Chemistry and Technology, University of Split, R. Boškovića 35, 21000 Split, Croatia J Solid State Electrochem DOI 10.1007/s10008-016-3234-3