This paper reports on the development and characterization of Prussian Blue-modified carbon paste electrodes. New methods of matrix modification with Prussian Blue are reported. Two different carbon pastes have been prepared, using mineral oil or solid paraffin, thus obtaining different types of sensors whose behavior toward the electrochemical reduction of hydrogen peroxide has been fully characterized. Results obtained with Prussian Bluemodified electrodes showed a long operational lifetime, an excellent stability in a wide range of pH (3-9), a high sensitivity, and a fast response time. In addition, the coupling of solid carbon paste modified with Prussian Blue and the enzymes glucose oxidase and choline oxidase led to the assembling of biosensors that showed an optimum working range at alkaline pH. Potassium iron(III)hexacyanoferrate(II) or Prussian Blue (PB)is an inorganic polycrystal with well-known electrochromic and electrocatalytical properties. Since it was deposited on solid electrodes by Neff, 1 it has been the subject of many studies: because of its changes in color (colorless when reduced to Prussian White, yellow when oxidized to Prussian Yellow), this compound has been employed in the development of electrochromic devices; 2,3 it can be used as a power source in rechargeable batteries, 4 and its electrocatalytical properties have been investigated by Itaya and co-workers, who first described an electrochemical method for growing PB films and their electrochemical behavior. 5,6 They showed that the reduced form of PB, the Prussian White, does have a catalytic activity for the reduction of O 2 and H 2 O 2 and also the oxidized form of PB shows a catalytic activity for the oxidation of H 2 O 2 . 6 Others PB analogues, as Cu, Co, Cr, and Ni hexacyanometalates, have been used as electrocatalysts for developing electrochemical sensors for the detection of H 2 O 2 7-9 and other compounds such as perborate, 10 persulfate, 11 hydrazine, 12,13 and cytocrome c. 14 In fact, these transition metal hexacyanometalates are able to reduce the overpotential necessary for nonmodified electrodes to reduce or to oxidize of the previous mentioned species. 13 The ability of PB in reducing H 2 O 2 has attracted the attention of the biosensor community, and recently, in some papers, 15-17 PB has been defined as an "artificial peroxidase" because of its analogy with the biological family of peroxidase enzymes, responsible in nature for reduction hydrogen peroxide. 18 This reduction, in fact, occurs at electrodes modified by PB in different ways at a potential range between -200 and 0 mV (vs Ag/AgCl), defined as the "range offering the most sensitive and interference-free detection" 18 for amperometric biosensors. In fact, this range is low enough to reduce the signal of the electrochemical interfering species often present in real matrixes. In addition, PB does not lack in long-term stability and relatively high costs which are often related to the use of biological components.Recently, a considerable number of pap...

Electropolymerisation of nonconducting polymer, poly-(1,2-diaminobenzene) on the top of Prussian Blue (PB) modified electrode led to significant improvement of resulting hydrogen peroxide transducer selectivity and operational stability. The reported transducer retained 100% of response during 20 h under the continuous flow of 0.1 mM H 2 O 2 , and thus improves the stability level in selective peroxide detection by one order of magnitude. The selectivity value of the PB -poly(1,2-DAB) based H 2 O 2 sensor in relation to ascorbate is approximately 600. No signals to acetaminophen and urate were investigated. PB -poly(1,2-diaminobenzene) modified electrode allows the detection of H 2 O 2 in the flow-injection mode down to 10 À 7 M with the sensitivity 0.3 A M À 1 cm À 2 , which is only two times lower compared to the uncovered PB based transducer. D

An approach to improve the analytical performance of a Prussian Blue (PB)-based hydrogen peroxide transducer is described. In support of this objective, both the stabilizing and anti-interferent properties of nonconducting films were used. Electropolymerization on the top surface of PB modified electrodes is possible due to the high oxidizing ability of Berlin Green, and the growth of nonconductive polymers may be independently monitored by investigating the redox activity of the inorganic polycrystal. The best performance characteristics, which are advantageous over existing H 2 O 2 sensors, were obtained for PB electrodes covered with electropolymerized o-phenylenediamine (1,2-diaminobenzene). The reported transducer remained at the 100% response state for more than 20 h under continuous flow of 0.1-mM hydrogen peroxide (flow rate 1 ml min 1 ), which improves the stability level among the selective H 2 O 2 sensors by one order of magnitude. The selectivity factor of the PB-poly (1,2-diaminobenzene) based transducer relative to ascorbate is nominally 600. PB-poly(1,2-diaminobenzene) modified electrode allows the detection hydrogen peroxide in the flow-injection mode down to 10 7 M with sensitivity of 0.3 A M 1 cm 2 , which is two times lower compared to the uncovered PB-based transducer.

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