Feature Article Investigation of the Effect of Different Glassy Carbon Materials on the Performance of Prussian Blue Based Sensors for Hydrogen Peroxide Francesco Ricci, a Giuseppe Palleschi, a Yirgalem Yigzaw , b Lo Gorton*, b TautgirdasRuzgas , b Arkady Karyakin c a Dipartimento di Scienze e Tecnologie Chimiche, Universita ¡ di Roma Tor Vergata, Via della Ricerca Scientifica, 00133 Roma, Italy b Department of Analytical Chemistry, Lund University P.O. Box 124, SE-221 00 Lund, Sweden; e-mail: Lo.Gorton@analykem.lu.se c Faculty of Chemistry, M.V. Lomonosov Moscow University State University, 119899, Moscow, Russia Received: April 2, 2002 Final version: June 18, 2002 Abstract Three different kinds of glassy carbon (GC-R, GC-K, GC-G) were equally pretreated, further modified with electrochemically deposited Prussian Blue and used as sensors for hydrogen peroxide at an applied potential of  50 mV (vs. Ag j AgCl). Their performance was evaluated with respect to the following parameters: the coverage and electrochemistry of the electrodeposited Prussian Blue, the sensitivity and the lower limit of detection for hydrogen peroxide, and the operational stability of the sensors. GC-R showed the best behavior concerning the surface coverage and the operational stability of the electrodeposited Prussian Blue. For this electrode the sensitivity for hydrogen peroxide (10 mM) was 0.25 A/M cm 2 and the detection limit was 0.1 mM. Scanning electron microscopy was used to study the surfaces of the three electrodes before and after the electrodeposition of Prussian Blue and to search for the reason for the three different behaviors between the different glassy carbon materials. The Prussian Blue modified GC-R was also used for the construction of a glucose biosensor based on immobilizing glucose oxidase in Nafion membranes on top of electrodeposited Prussian Blue layer. The operational stability of the glucose biosensors was studied in the flow injection mode at an applied potential of  50 mV (vs. Ag j AgCl) and alternatively injecting standard solutions of hydrogen peroxide (10 mM) and glucose (1 mM) for 3 h. For the GC-R based biosensor a 2.8% decrease of the initial glucose response was observed. Keywords: Glassy carbon, Prussian Blue, Hydrogen peroxide, Glucose, Nafion 1. Introduction Sinceitwasannouncedalmost25yearsago[1],thatPrussian Blue or ferric ferrocyanide, electrodeposited onto an electrode surface, could act as an electrocatalyst for hydro- gen peroxide reduction, many attempts were made to achieve a suitable catalytic surface for the amperometric determination of hydrogen peroxide [2, 3]. Both the electrodes material (Pt [4], Au [5], graphite [5±7], carbon paste [8], glassy carbon [9, 10]) and the techniques of immobilization of Prussian Blue (mechanical immobiliza- tion, electrodeposition [11, 12] etc.) were tested. The main advantage of electrodeposited Prussian Blue relies on the fact that hydrogen peroxide can be detected selectively through electrocatalytic reduction in the pres- ence of molecular oxygen [13], at a low electrode potential ( 0.05 V vs. SCE), where the influence of the so-called reductants (ascorbate, urate, acetaminophen) on the elec- trochemicalresponsecanbelargelyavoided[14±16],which is always a common problem for systems based on the electrochemicaloxidationofhydrogenperoxide.Moreover, it is known that the detection of hydrogen peroxide plays a very important role for the construction of many electro- chemical biosensors [15 ± 18], since the hydrogen peroxide producing oxidases such as, glucose, lactate, alcohol, gluta- mate oxidase, etc., commonly used for biosensor construc- tion,intheirreactionsequencestartingwiththeoxidationof their substrate produce hydrogen peroxide as an end product that in turn is measured. A glucose biosensor, using glassy carbon as basic electrode material, can thus be obtained by initially electrodepositing Prussian Blue fol- lowed by immobilizing glucose oxidase. These kind of glucose biosensors have been found exhibiting high sen- sitivity and linear behavior in a broad concentration range [2, 19, 20]. Similarly ethanol, glutamate, oxalate, choline, d-alanine, and l-lactate biosensors have been produced [2, 3]. The aim of this work was to investigate and compare the effects of different glassy carbon materials on the sensor performance. The reason for focusing on glassy carbon is that it is a cheaper electrode material than the noble metals and it has lower background current and noise levels than other carbon materials, e.g., graphite, and compared with both platinum and graphite it is less prone to catalyze possibleinterferingelectrochemicalreactions.Additionally, previous reports on Prussian Blue modified glassy carbon electrodes reveal promising properties as selective sensors for hydrogen peroxide. Three different kinds of glassy carbon were used for the construction of Prussian Blue modified glucose biosensors. The electrodeposition of 175 Electroanalysis 2003, 15, No. 3 ¹ 2003 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim 1040-0397/03/0302-0175 $ 17.50+.50/0