Mmol Dm Research Articles

Structural, optical and electrical properties of ZnTe thin films electrochemically deposited from a citric acid aqueous solution

ZnTe thin films were electrodeposited onto Au-coated Cu substrates from an electrolytic solution containing ZnSO4, TeO2, citric acid and sodium citrate, and the dependence of structure, composition and surface morphology on the solution's Zn concentration were investigated. Results of examinations for resistivity and optical absorption demonstrated, respectively, that as the Zn concentration in the electrolyte was reduced over the range of 5–50 mmol dm−3, the resistivity of the films obtained continuously decreased and their band gap increased. Quantative analysis of energy dispersive x-ray analysis and inductively coupled plasma results indicated that the composition ratio (Zn : Te) was approximately stoichiometric under all conditions in this study. X-ray diffraction results revealed that all the ZnTe thin films obtained showed a preferred (111) orientation with cubic structure. ZnTe thin films we transferred onto nonconductive epoxy resin also showed the same structure.

Application of Prussian Blue Based Composite Film with Functionalized Organic Polymer to Construction of Enzymatic Glucose Biosensor

AbstractWe describe and characterize an amperometric biosensor utilizing the electrocatalytic reduction of hydrogen peroxide at a glassy carbon electrode modified with a novel composite film of Prussian Blue and polypyrrole derivative, polymerized 4(pyrrole‐1‐yl) benzoic acid, overcoated with the covalently bound glucose oxidase enzyme. The addition of a functionalized organic component to Prussian Blue permits permanent attachment of an enzyme, exhibits an overall stabilizing effect, and it seems to support fast propagation of charge within the Prussian Blue based composite film. Preliminary diagnostic experiments have been done using cyclic voltammetry, chronocoulometry and rotating disk volatmmetry. The rate of hydrogen peroxide reduction at the composite film in the potassium containing phosphate buffer (pH 6) is expected to be very fast because the overall process is controlled by diffusion of hydrogen peroxide in solution. The fact that the reduction of enzymatically produced hydrogen peroxide proceeds at a fairly negative potential, 0 V (vs. SCE) (pH 6), makes the system largely free of common interferences (e.g., ascorbic acid or uric acid). The proposed biosensor permitted reproducible and reliable determinations of glucose in real (i.e., in pharmaceutical and food) samples also under the flow‐injection analysis conditions. The detection limit and sensitivity have been found to be on the level of 1×10−5 mol dm−3 and 0.7 μA/1 mmol dm−3 (2.5 μA/cm2/1 mmol dm−3), respectively.

Micelle formation of sodium chenodeoxycholate and solubilization into the micelles: comparison with other unconjugated bile salts

Micellization of sodium chenodeoxycholate (NaCDC) was studied for the critical micelle concentration (CMC), the micelle aggregation number, and the degree of counterion binding to micelle at 288.2, 298.2, 308.2, and 318.2 K. They were compared with those of three other unconjugated bile salts; sodium cholate (NaC), sodium deoxycholate (NaDC), and sodium ursodeoxycholate (NaUDC). The I 1/ I 3 ratio of pyrene fluorescence and the solubility dependence of solution pH were employed to determine the CMC values. As the results, a certain concentration range for the CMC and a stepwise molecular aggregation for micellization were found reasonable. Using a stepwise association model of the bile salt anions, the mean aggregation number ( n̄) of NaCDC micelles was found to increase with the total anion concentration, while the n̄ values decreased with increasing temperature; 9.1, 8.1, 7.4, and 6.3 at 288.2, 298.2, 308.2, and 318.2 K, respectively, at 50 mmol dm −3. The results from four unconjugated bile salts indicate that the number, location, and orientation of hydroxyl groups in the steroid nucleus are quite important for growth of the micelles. Activity of the counterion (Na +) was determined by a sodium ion selective electrode in order to confirm the low counterion binding to micelles. The solubilized amount of cholesterol into the aqueous bile salt solutions increased in the order of NaUDC<NaC<NaCDC<NaDC. The first stepwise association or solubilization constants ( K̄ 1) between a cholesterol monomer and a vacant micelle were evaluated at different bile salt concentrations. The constants were also determined for polycyclic aromatic compounds (benzene, naphthalene, anthracene, and pyrene). The corresponding Δ G 0 value was most negative for cholesterol among the solubilizates studied, which indicated that cholesterol was thermodynamically stabilized most by solubilization into the bile salt micelles.

Lignin peroxidase‐catalyzed polymerization and detoxification of toxic halogenated phenols

AbstractHalogenated phenols and bisphenols are recognized as being recalcitrant in conventional biological treatments. The current research evaluated lignin peroxidase‐catalyzed oxidation and polymerization as a potential alternative for their detoxification. Gel permeation–HPLC analysis demonstrated the formation of dimers, trimers and tetramers upon oxidation of the target substrates. Polymerization was accompanied by effective detoxification of the aqueous phase during oxidation of 2,4‐dibromophenol, the extent of which correlated with the extent of oxidation and polymerization. Steady state kinetic measurements at a saturating concentration of H2O2 revealed high Km values (270–1100 µmol dm−3) for the target substrates, reflecting the strong electron‐withdrawing properties of halogen substituents, which increase the oxidation potential of the phenols, resulting in thermodynamically less favorable reactions. However, kcat values were not dissimilar from non‐halogenated phenols and the rapid oxidation and polymerization suggests that low retention times could be expected in a continuous process for their treatment, in contrast to conventional biological methods. The operational stability of lignin peroxidase was significantly improved by inclusion of redox mediators, which resulted in enhanced oxidation and more rapid reaction rates. However, due to their inherent toxicity, the use of redox mediators impeded toxicity assays. The findings highlight the potential of lignin peroxidase as a possible alternative for the high‐rate treatment of industrial wastewater when conventional methods are ineffective. Copyright © 2003 Society of Chemical Industry

Decomposition of 2,4-dichlorophenoxyacetic acid by ozonation, ionizing radiation as well as ozonation combined with ionizing radiation

Electron beam (EB), ozone (O 3) and the combination EB/O 3 were used to study the oxidative decomposition of 2,4-dichlorophenoxyacetic acid (2,4-D) in local tap water. Using an EB treatment, a dose of 10 kGy was required for complete 2,4-D degradation, and a 90% conversion of organic chlorine into chloride ions. Using additionally 1.33 mmol dm −3 O 3 during irradiation, the same result was achieved with a dose of 2.7 kGy. The yields of products acetate and formate were almost doubled by the combined EB/O 3 treatment, compared to those obtained with the same dose by EB irradiation. Gamma radiolysis showed that the degradation dose was proportional to the initial concentration of 2,4-D in the range of 50–2260 μmol dm −3.

Decolourization and COD removal from reactive dye‐containing wastewater using sonophotocatalytic technology

AbstractDecolourization and COD removal from synthetic wastewater containing Reactive Brilliant Orange K‐R (RBOKR) dye using sonophotocatalytic technology was investigated. Experimental results showed that this hybrid technology could efficiently remove the colour and reduce COD from the synthetic dye‐containing wastewater, and that both processes followed pseudo first‐order kinetics. At the condition of 0.1 m3 h−1 airflow, 0.75 g dm−3 titanium dioxide and 0.5 mmol dm−3 RBOKR solution, the rate constants of decolourization and COD removal were 0.0750 and 0.0143 min−1 respectively for the sonophotocatalytic process; 0.0197 and 0.0046 min−1 respectively for the photocatalytic process and 0.0005 and 0.0001 min−1 respectively for the sonochemical process. The rate constants of sonophotocatalysis were greater than that of both the photocatalytic and sonochemical processes either in isolation or as a sum of the individual process, indicating an apparent synergetic effect between the photo‐ and sono‐processes. Copyright © 2003 Society of Chemical Industry

Dependence of the Electrochemical Response of Ferritin on the Number of Iron Atoms at the Ferritin Core

Abstract The well-defined redox reaction of ferritin was observed at an indium oxide electrode with a fully hydrophilic surface at a low concentration of ferritin solution (0–7 μmol dm−3). This was a diffusion-controlled electrode reaction process. Conversely, at a higher concentration of ferritin (7 μmol dm−3 &amp;lt;), ferritin was weakly adsorbed on the electrode surface. The electrochemical redox response of ferritin was strongly affected by the number of iron atoms at the core of the ferritin molecule.

Cellulose based macromolecular chelator having pyrocatechol as an anchored ligand: synthesis and applications as metal extractant prior to their determination by flame atomic absorption spectrometry

Pyrocatechol is immobilized on cellulose via NHCH 2CH 2NHSO 2C 6H 4NN linker and the resulting macromolecular chelator characterized by IR, TGA, CPMAS 13C NMR and elemental analyses. It has been used for enrichment of Cu(II), Zn(II), Fe(III), Ni(II), Co(II), Cd(II) and Pb(II) prior to their determination by flame atomic absorption spectrometry (FAAS). The pH ranges for quantitative sorption (98.0–99.4%) are 4.0–7.0, 5.0–6.0, 3.0–4.0, 5.0–7.0, 5.0–8.0, 7.0–8.0 and 4.0–5.0, respectively. The desorption was found quantitative with 0.5 mol dm −3 HCl/HNO 3 (for Pb). The sorption capacity of the matrix for the seven metal ions has been found in the range 85.3–186.2 μmol g −1. The optimum flow rate of metal ion solution for quantitative sorption of metal onto pyrocatechol functionalized cellulose as determined by column method, is 2–6 cm 3 min −1, whereas for desorption it is 2–4 cm 3 min −1. The tolerance limits for NaCl, NaBr, NaI, NaNO 3, Na 2SO 4, Na 3PO 4, humic acid, EDTA, ascorbic acid, citric acid, sodium tartrate, Ca(II) and Mg(II) in the sorption of all the seven metal ions are reported. Ascorbic acid is tolerable up to 0.8 mmol dm −3 with Cu and Pb where as sodium tartrate does not interfere up to 0.6 mmol dm −3 with Pb. There is no interference of NaBr, NaCl and NaNO 3 up to a concentration of 0.5 mol dm −3, in the sorption of Cu(II), Cd(II) and Fe(III) on to the chelating cellulose matrix The preconcentration factors are between 75 and 300 and t 1/2 values ≤5 min for all the metal ions. Simultaneous sorption of Cu, Zn, Ni and Co is possible at pH 5.0 if their total concentration does not exceed lowest sorption capacity. The present matrix coupled with FAAS has been used to enrich and determine the seven metal ions in river and tap water samples (relative standard deviation (R.S.D.) 1.05–7.20%) and synthetic certified water sample SLRS-4 (NRC, Canada) with R.S.D. ∼2.03%. The cobalt present in pharmaceutical vitamin tablets was also preconcentrated on the modified cellulose and determined by FAAS (R.S.D. ∼1.87%).

First steps in radiation-induced hydrogel synthesis: radical formation and oligomerization in dilute aqueous N-isopropylacrylamide solutions

The reactions of hydroxyl radical, hydrogen atom and hydrated electron intermediates of water radiolysis with N-isopropylacrylamide (NIPAAm) were studied by pulse radiolysis in dilute aqueous solutions. OH, H and e aq − react with NIPAAm with rate coefficient of (6.9±1.2)×10 9, (6.6±1)×10 9, and (1.0±0.2)×10 10 mol −1 dm 3 s −1. In OH and H radical addition to the double bond mainly α-carboxyalkyl type radicals form, (OHCH 2CH C(N- i-C 3H 7)O and CH 3CH C(N- i-C 3H 7)O). In reaction of e aq − oxygen atom centered radical anion is produced (CH 2CHC (N- i-C 3H 7)O − ), the anion undergoes reversible protonation with p K a=8.7. There is also an irreversible protonation on the β-carbon atom that produces the same radical as forms in H atom reaction (CH 3CH C(N- i-C 3H 7)O). The α-carboxyalkyl type radicals at low NIPAAm concentration (0.1–1 mmol dm −3) mainly disappear in self-termination reactions, 2 k t,m=8.4×10 8 mol −1 dm 3 s −1. At higher concentrations the decay curves reflect the competition of the self-termination and radical addition to monomer (propagation). The termination rate coefficient of oligomer radicals containing a few monomer units is 2 k t≈2×10 8 mol −1 dm 3 s 1.

Comparative biosorption of mercuric ions from aquatic systems by immobilized live and heat-inactivated Trametes versicolor and Pleurotus sajur-caju

Trametes versicolor and Pleurotus sajur-caju mycelia immobilized in Ca-alginate beads were used for the removal of mercuric ions from aqueous solutions. The sorption of Hg(II) ions by alginate beads and both immobilized live and heat-killed fungal mycelia of T. versicolor and P. sajur-caju was studied in the concentration range of 0.150–3.00 mmol dm −3. The biosorption of Hg(II) increased as the initial concentration of Hg(II) ions increased in the medium. Maximum biosorption capacities for plain alginate beads were 0.144 ± 0.005 mmol Hg(II)/g; for immobilized live and heat-killed fungal mycelia of T. versicolor were 0.171 ± 0.007 mmol Hg(II)/g and 0.383 ± 0.012 mmol Hg(II)/g respectively; whereas for live and heat-killed P. sajur-caju, the values were 0.450 ± 0.014 mmol Hg(II)/g and 0.660 ± 0.019 mmol Hg(II)/g respectively. Biosorption equilibrium was established in about 1 h and the equilibrium adsorption was well described by Langmuir and Freundlich adsorption isotherms. Between 15 and 45 °C the biosorption capacity was not affected and maximum adsorption was observed between pH 4.0 and 6.0. The alginate-fungus beads could be regenerated using 10 mmol dm −3 HCl solution, with up to 97% recovery. The biosorbents were reused in five biosorption–desorption cycles without a significant loss in biosorption capacity. Heat-killed T. versicolor and P. sajur-caju removed 73% and 81% of the Hg(II) ions, respectively, from synthetic wastewater samples.

The different phases in the precipitation of dicalcium phosphate dihydrate

Abstract The precipitation of dicalcium phosphate dihydrate, brushite, by mixing a calcium hydroxide suspension and an orthophosphoric acid solution in equimolar quantities, has been investigated in a batch system at 25°C. The concentration of calcium hydroxide and orthophosphoric acid, before mixing, ranged from 50 to 300 mmol dm−3. The phase first precipitated is Ca5OH(PO4)3, hydroxyapatite. The precipitation process of brushite is divided into five stages and is similar for all initial experimental conditions. The extension of each stage varies with the initial reagents’ concentrations. These stages are discussed individually as a function of pH and reagents’ concentrations. The precipitate was analysed by scanning electron microscopy and X-ray diffraction. The solubility of brushite was determined at 25°C, 30°C and 35°C, and in the pH range 4.5–8.

Synthesis, structure and properties of an imidazolate-bridged dicopper complex of a novel macrocycle with two alcohol-pendants as an active site model of Cu,Zn-SOD

The imidazolate-bridged dicopper complex of a macrocyclic ligand with two hydroxyethyl pendants L, L=3,6,9,17,20,23-hexaza-6,20-bis(2-hydroxyethyl)-tricyclo[23.3.1.1. 11,15]triaconta-1(29),11(30),12,14,25,27-hexaene, has been synthesized as a possible model for Cu,Zn-SOD. Single-crystal X-ray analysis revealed the geometry of the imidazolate-bridged CuCu center, and the distance between the two Cu(II) ions is 5.8135(9) Å. The two metals are each pentacoordinated with geometries between trigonal-bipyramid (TBP) and tetragonal-pyramid (TP). Magnetic measurement of the imidazolate-bridged dicopper complex exhibited the presence of an antiferromagnetic exchange interaction with a coupling constant of −2 J=72.8 cm −1. Investigation on the pH-dependent ESR of the complex in frozen 50% aqueous DMSO solution at 110 K revealed the existence of the imidazolate-bridged dicopper structure in solution mainly in the range 5.5≤pH≤12. The SOD activity of the complex has been evaluated by the nitro blue tetrazolium assay and the complex catalyzed the dismutation of superoxide at pH 7.8 with an IC 50 value of 0.36 μmol dm −3.

Electrochemical polymerization of azure A and properties of poly(azure A)

The electrochemical polymerization of azure A has been carried out using repeated potential cycling. The scan potential is set between −0.2 and 1.3 V (vs. Ag/AgCl). The electrolytic solution consisted of 5 mmol dm−3 azure A and 0.5 mol dm−3 Na2SO4 with pH 6.0. The temperature for polymerization was controlled at 50°C. An anodic peak and a cathodic peak appear at 0.38 and 0.23 V, respectively, on the cyclic voltammogram of poly(azure A) in 0.5 mol dm−3 Na2SO4 solution of pH 1.0. Their peak potentials shift toward the negative direction as pH value increases from 1.0 to 4.0. Poly(azure A) has good electrochemical activity and stability in the aqueous solution at the above pH range. The UV-visible spectrum and FTIR spectrum of poly(azure A) are different from those of azure A. The FTIR spectrum of poly(azure A) indicates that no anions were doped into the oxidation form of poly(azure A). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1218–1224, 2003

The interaction of glass-ionomer cements containing vinylphosphonic acid with water and aqueous lactic acid.

A glass-ionomer cement containing an acrylic acid/vinyl phosphonic acid copolymer, has been investigated for its interaction with water and with aqueous lactic acid and the results compared with those from conventional glass-ionomers based on polyacrylic acid. Cylindrical specimens (12 mm high x 6 mm diameter) were placed in 8 cm3 of aqueous lactic acid (20 mmol dm(-3); pH 2.7) for 1 week, at the end of which the pH was determined. Each specimen was then placed in a fresh 8 cm3 volume of lactic acid and the pH determined after a further week. This procedure was continued for a total of 13 weeks for each specimen. Experiments were also carried out on similar specimens exposed to 8 cm3 of water for 1 week only. Further experiments were carried out in which discs of cement were exposed to thin films (0.15 mm) of lactic acid at pH 4.5, with pH values determined at 30 s, 1, 2, 5 and 10 min. After 1 week, cements had changed the pH of the lactic acid to a mean value of 3.63 (SD 0.08) while in weeks 2-13 they changed it to a mean value of 3.31 (SD 0.11). After 1 week in aqueous lactic acid the cements had gained mass by a mean of 1.26% (SD 0.59%) compared with 1.22% (SD 0.14%) in water. After 13 weeks in lactic acid, cements had lost a mean of 2.83% (SD 0.74%) in mass. Thin films of aqueous lactic acid changed from pH 4.5-5.1 at 30 s and to a steady value of 5.6 (SD 0.3) between 2 and 10 min. These results were similar to those for conventional glass-ionomer cements based on carboxylic acid polymers. Hence, it was concluded that the presence of the vinylphosphonic acid units made no significant difference to the interaction of cements with aqueous solutions.

Inorganic plasma with physiological CO 2/HCO 3− buffer

The substitution of tris/HCl buffer by CO 2/HCO 3 − buffer in inorganic plasma was studied. An appropriate gas mixture of CO 2/N 2 was continuously bubbled in Kokubo's SBF solution prepared without addition of Tris/HCl. This method enables buffering the solution within the 7.3–7.4 pH interval and, at the same time, reaching a HCO 3 − concentration between 24 and 27 mmol dm −3, which are the normal concentrations reported for blood plasma. Mineralisation studies on calcium phosphate ceramics using this solution showed that, in the presence of such hydrogencarbonate concentrations, the formation of a mineralisation layer on the ceramic occurs via a carbonated octacalcium phosphate, that evolves to carbonated hydroxyapatite. The results suggest that mineralisation studies in this new carbonate-containing simulated inorganic plasma mimic biomineralisation more closely than traditional SBF.

Tris (2,2′-bipyridil) copper (II) chloride complex: a biomimetic tyrosinase catalyst in the amperometric sensor construction

The use of tris (2,2′-bipyridil) copper (II) chloride complex, [Cu(bipy) 3]Cl 2·6H 2O, as a biomimetic catalyst, is reported in the construction of an amperometric sensor for dopamine. The sensor was prepared modifying a glassy carbon electrode with a Nafion® membrane doped with the complex. The optimized conditions for the sensor response were obtained in 0.25 mol dm −3 Pipes buffer (pH 7.0) containing 150 μmol dm −3 H 2O 2, with an applied potential of −50 mV versus saturated calomel electrode (SCE). In these conditions, a linear response range between 9 and 230 μmol dm −3, with a sensitivity of 1.43±0.01 nA dm 3 μmol −1 cm −2 and a detection limit of 4.8 μmol dm −3 were observed for dopamine. The response time for this sensor was about 1 s, presenting the same response for at least 150 successive measurements, with a good repeatability (4.8%) expressed as relative standard deviation for n=13. After its construction, this sensor can be used after 180 days without loss of sensitivity, kept at room temperature. The difference of the sensor response between four preparations was 4.2%. A detailed investigation about the sensor response for other eighteen phenolic compounds and five interfering species was performed. The sensor was applied for dopamine determination in pharmaceutical preparation with success.

Selective determination of beryllium(II) ion at picomole per decimeter cubed levels by kinetic differentiation mode reversed-phase high-performance liquid chromatography with fluorometric detection using 2-(2'-hydroxyphenyl)-10-hydroxybenzo[H]quinoline as precolumn chelating reagent.

A highly sensitive and selective method for the determination of the Be(II) ion has been developed by the use of reversed-phase high-performance liquid chromatography (HPLC) with fluorometric detection using 2-(2'-hydroxyphenyl)-10-hydroxybenzo[h]quinoline (HPHBQ) as a precolumn (off-line) chelating reagent. The reagent HPHBQ has been designed to form the kinetically inert Be chelate compatible with high fluorescence yield, which is appropriate to the HPLC-fluorometric detection system. The Be-HPHBQ chelate is efficiently separated on a LiChrospher 100 RP-18(e) column with a methanol (58.3 wt %)-water eluent containing 20 mmol kg(-1) of tartaric acid and is fluorometrically detected at 520 nm with the excitation at 420 nm. Under the conditions used, the concentration range of 20-8,000 pmol dm(-3) of Be(II) ion can be determined without interferences from 10 micromol dm(-3) each of common metal ions, typically Al(III), Cu(II), Fe(III), and Zn(II), and still more coexistence of Ca(II) and Mg(II) ions at 0.50 mmol dm(-3) and 5.0 mmol dm(-3), respectively, is tolerated. The detection limit (3a baseline fluctuation) is 4.3 pmol dm(-3) (39 fg cm(-3)). The extraordinarily high sensitivity with toughness toward the matrix influence was demonstrated with the successful application to environmental Be analyses, such as determination of Be in rainwater and tap water.

Effects of Chloride and Bromide Ions on Sequential Oscillations in the Uncatalyzed Bromate Oscillator

The uncatalyzed system BrO3--phenol-H2SO4 exhibits an astonishing variety of dynamic behaviour, including sequential oscillations in a closed, stirred batch reactor. The effect of initial addition of chloride and bromide ions on a sequential oscillating system has been studied. Various results were obtained, depending on the initial chloride and bromide concentrations. Increasing the concentration of chloride ions (from 5 × 10-5 to 6 × 10-4 mol dm-3), the parameters of sequential oscillations changed. The number of first oscillations increased from 4 to 21 and their amplitude decreased. The duration of the non-oscillatory period and the number of second oscillations decreased from 96 to 26 min and from 8 to 1, respectively. In the concentration range 3.5 mmol dm-3 &lt; [Br-]o &lt; 8.0 mmol dm-3, the system displays a dual-frequency, dual-amplitude and aperiodic oscillations with a transition period between high- and low-frequency oscillations. The induced oscillations were also observed when the system was perturbed by chloride or bromide ions. The oxidation of pyrocatechol with bromate is an autocatalytic reaction; the rate constants corresponding to the uncatalyzed and catalyzed reactions were evaluated and used in numerical simulations.

Enzymatic Oxidative Polymerization of 4-Chloroguaiacol by Laccase

The kinetics of enzymatic oxidative polymerization of 4-chloroguaiacol by laccase was studied. 4-Chloroguaiacol, a model compound of the chloroguaiacols formed in the bleaching process in the pulp industry, was oxidized by laccase from Trametes sp. Ha1 to eliminate chloroguaiacols from pulp wastewater by polymerization and precipitation. On the basis of the reaction rate obtained from the decrease in the 4-chloroguaiacol concentration, the optimum pH of the reaction was 4–5 and the apparent Michaelis constant Km for the reaction was more than 5 mmol dm–3. However, the value of Km obtained from the dependence of oxygen consumption rate on the concentration of 4-chloroguaiacol was 0.092 mmol dm–3. The reaction rate was expressed as the sum of the enzymatic oxidation rate of 4-chloroguaiacol and the polymerization rate of the radical formed in the enzymatic oxidation. The kinetics of the enzymatic oxidative polymerization shown in this study will be useful to understand those of the enzymatic oxidation of other phenolic compounds.

Characteristics of pyridine adsorption on Au(111) and Au(210) by EIS parameters fitting procedure

Some aspects of the application of electrochemical impedance spectroscopy to studies of solid electrode / solution interface, in the absence of faradaic processes, are analysed. In order to perform this analysis, gold electrodes with (111) and (210) crystallographic orientations in an aqueous solution containing 10 mmol dm-3 KF, as supporting electrolyte, and a pyridine concentration varying from 0.01 to 4.6 mmol dm-3, were used. The experimental data was analysed by using EQUIVCRT software, which utilises non-linear least squares routines, attributing to the solid electrode / solution interface behaviour described by an equivalent circuit with a resistance in series with a constant phase element. The results of this fitting procedure were analysed by the dependence on the electrode potential on two parameters: the pre-exponential factor, Y0, and the exponent n f, related with the phase angle shift. By this analysis it was possible to observe that the pyridine adsorption is strongly affected by the crystallographic orientation of the electrode surface and that the extent of deviation from ideal capacitive behaviour is mainly of interfacial origin.