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In this work the oxidation and reduction reactions of MnIII–Coproporphyrin-I (MnIII-CPI) have been studied and four forms of manganese–CPI complexes have been characterized. This complex was observed to be highly reactive (at basic pH) towards Mn(II), hypochlorite, hydrogen peroxide and oxone, forming [MnIV(O)CPI(OH)]− that was unstable and, after a short time, formed again [MnIIICPI(OH)2]−. With an excess of NaClO, a further oxidation of the complex [MnIV(O)CPI(OH)]−, provoked a significant spectral change for the [MnV(O)CPI(OH)] formation that showed, in the time, a partial polymerization. [MnIIICPI(OH)2]− was reduced by sodium dithionite to form the very unstable complex of [MnIICPI(OH)]− that successively degraded with Mn(II) release.

The aggregation of astaxanthin in hydrated methanol was kinetically studied in the temperature range from 10 degrees C to 50 degrees C, at different astaxanthin concentrations and solvent composition. A kinetic model for the formation and transformation of astaxanthin aggregated has been proposed. Spectrophotometric studies showed that monomeric astaxanthin decayed to H-aggregates that after-wards formed J-aggregates when water content was 50% and the temperature lower than 20 degrees C; at higher temperatures, very stable J-aggregates were formed directly. Monomer formed very stable H-aggregates when the water content was greater than 60%; in these conditions H-aggregates decayed into J-aggregates only when the temperature was at least 50 degrees C. Through these findings it was possible to establish that the aggregation reactions took place through a two steps consecutive reaction with first order kinetic constants and that the values of these depended on the solvent composition and temperature.

The coproporphyrin-I (CPI) behaves as a reducing agent for silver and gold metal ions and as stabilizing agent for the formed colloidal metallic nanoparticles. The peculiarity of silver and gold nanoparticles obtained in the reactions of monomeric form of CPI with their metal ions has been studied. The optical properties of the colloidal forms of these metals have been investigated by UV–Vis spectrophotometry, and their morphology by TEM and SEM measurements. The structures and the size distributions of Ag and Au particles have been characterized and determined by computerized TEM images.

The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) with the elements of 11 group have been studied. CPI is an anionic porphyrin that slowly reacts with copper ion to form Cu II CPI and with silver ions to form Ag II CPI, Ag III CPI complexes and colloidal silver. Gold ions do not form complexes with CPI, but, in the main, colloidal gold and some CPI- N -oxide. The kinetics of the reactions with copper and silver were spectrophotometerically studied and the rate constants were calculated. The identification and characterization of this water-soluble anionic porphyrin and its metal complexes have been performed by electrospray mass spectrometry (ESI-MS) that proved to be an excellent method for these determinations. The multiple charged parent ions for metal free ligand and their metal complexes were identified.

The chromatographic behavior of multiply charged analytes in ion interaction chromatography (IIC) was theoretically investigated. Practical equations that describe the relationship between the retention factor and the concentration of the ion interaction reagent (IIR) were developed. They can be used to model analyte retention as a function of both the mobile and stationary phase concentrations of the IIR. A comparison between the retention behaviour of singly and doubly charged analytes is given.

When dropping mercury electrode (DME) dipped in ultrapure water, thoroughly deaerated with pure hydrogen, is irradiated with UV light, we can observe a cathodic photocurrent in the non-faradaic region of the polarographic curve, in the absence of scavengers of hydrated electrons. Newly we have followed the effect on photocurrent of initial very small additions of alkali metal chlorides to pure water. By repeated experiments, we could show that first additions of the alkali metal halides increase the photocurrent and that the already known suppression of photocurrent by addition of halides begins only after the halide concentration exceeds ca 10-4 mol l-1. We could show for the first time that in ultrapure water and dilute electrolyte solutions, the photocurrent follows a modified seven-halves law. The extent of the positive effect of small additions of alkali metal halides on photocurrent depends on the nature of each alkali metal cation. The reason for this specificity is discussed.

The chromatographic behavior of zwitterions in Ion-interaction chromatography (IIC) is, investigated theoretically for the first time. The modification of the stationary phase in the presence of Ion-interaction reagent (IIR), and adsorption competition between test analytes and IIR for inner layer sites are shown theoretically to change the partition coefficient for zwitterions. Experimental results from the literature concerning retention behavior of zwitterions in IIC, were used to test the new thermodynamic theory. Very reasonable estimates of (i) ΔG o values for the IIR adsorption onto the stationary phase (II) total ligand concentration, and (iii) dipolar moments validate the present thermodynamic model for the IIC of zwitterionic analytes. Retention equations are compared to those which can be obtained, if the net charge of the analyte is zero, from the most important retention models in IIC. None of them is able to explain, even in a qualitative way, the retention behavior of zwitterions in IIC whereas, the present model is quantitatively able to do this.

The chromatographic behavior of neutral molecules in ion-interaction chromatography (IIC) is investigated theoretically. The physical and chemical modification of the stationary phase in the presence of ion interaction Reagent (IIR) in the eluent, and adsorption competition between test analytes and IIR for inner layer sites are shown theoretically to change the partition coefficient of neutral molecules.

The chromatographic behavior of neutral molecules in Ion Interaction Chromatography (IIC) was theoretically investigated. The use of a potential approximation to obtain a simplified retention equation was successfully tested. The most reliable experimental literature results, concerning the retention behavior of neutral molecules in IIC, were successfully fitted by the retention equation. The wide variability among them was elucidated on the basis of the developed retention equation. A new separation strategy, to improve the selectivity of the chromatographic method, for difficult to separate mixtures of neutral eluates was proposed.

The quantitation of 2,6-pyridinedicarboxylic acids (2,6-PDA) in fruit juice can be achieved rapidly utilizing High Pressure Liquid Chromatography (HPLC). The best chromatographic performance was obtained with an aqueous mobile phase containing 15 mM tetrabutylammonium phosphate and 2 mM EDTA; the pH was maintained at 7.2 by 10 mM phosphate buffer. The influence of the eluent parameters on retention of PDAs has been investigated in order to elucidate the separation mechanisms involved in the ion pair chromatography of these ionizable substances.

Oleic or linoleic acid supported on barium sulphate was used to remove atrazine and terbuthylazine in the range of 0.1–2.0 μg/L using spiked water samples. The sorption of atrazine depends on the stirring time and the best value is 150 min. Terbuthylazine is removed well with a stirring time of 60 min and its adsorption is about 90%. Detection of the residual pesticide in treated waters, after solid phase extraction (SPE), was carried out by GC‐MS operating in selected ion monitoring (SIM) using a calibration curve by direct injection of standard solutions of herbicide.

The chromatographic performance of metal chelating analytes on a C18 silica based stationary phase was studied. The influence of metal ions impurities on their peak shapes and the metal ions exchan...

The chromatographic behavior of aprotic neutral molecules in Ion Interaction Chromatography (IIC) was investigated both theoretically and experimentally on a styrene-divinylbenzene based C18 stationary phase. The chemical modification of the stationary phase in the presence of Ion Interaction Reagent (IIR) in the eluent, and adsorption competition between tested analytes and IIR for inner layer sites are theoretically shown to change the partition coefficient for neutral molecules. Experimental evidence confirms that their retention decreases with increasing ion-interaction reagent (IIR) concentration in the eluent. The influence of the mobile phase ionic strength on neutral molecules retention was investigated and the dependence of retention modulus on organic modifier concentration in the eluent was elucidated.

The retention behaviour of aprotic neutral molecules in Ion Interaction Chromatography was investigated. The study demonstrates that their retention, for an aqueous mobile phase (phosphate buffer pH 7.2-methanol, 85:15 v/v) containing the ion-interaction reagent (IIR) in the range 0–25 mM, decreases with increasing IIR concentration. Silanophilic interactions were accounted for by comparison of results obtained with either a silica based or a styrene-divinylbenzene based C18 stationary phase, under otherwise identical conditions. The retention behaviour of neutral molecules was elucidated on the basis of the exhaustive Ion Interaction retention model and evidence was obtained to support the proposition that the decreased retention is the result of an adsorption competition between tested analytes and ion-interaction reagent for inner layer sites on the stationary phase.

ABSTRACT The use of potassium tetrakis(1H-pyrazolyl)borate KB(Pz)4 as a mobile phase additive for reverse phase High Performance Liquid Chromatography of metal chelating compounds was investigated. The reason for its superiority over previously employed eluent modifiers is described.

The separation and quantitation of the six isomers of pyridinedicarboxylic acids (PDAs) can be achieved rapidly utilizing High Pressure Liquid Chromatography (HPLC). Optimal separation is accomplished using reverse phase chromatography with an aqueous mobile phase mantained at a pH of 7.3 by 153.2 mM phosphate buffer, containing 15 mM tetrabutylammonium phosphate as ion-pairing agent and 2 mM EDTA as mobile phase additive. The influence of the eluent parameters on retention of PDAs has been investigated in order to elucidate the separation mechanisms involved in the ion pair chromatography of these ionizable substances.

A reproducible current-voltage curve of pure water, obtained with the dropping mercury electrode (DME), contains a 1-2 V wide region where no faradaic processes take place. This region consists of three distinct parts according to different orientations of water molecules and their interactions with the mercury surface. On irradiation of the DME by UV and visible light a cathodic photocurrent is produced in the negative part of the nonfaradaic region, which increases with increasing voltage. The photocurrent appears in water in the absence of scavengers of hydrated electrons, and its magnitude is of the same order as that of the current due to photoemission of electrons into solutions of electrolytes containing scavengers. Additions of electrolytes decrease and ultimately suppress this kind of photocurrent. We explain the photocurrent by the effect of an electric field of the extended electrode double layer on the return of hydrated electrons, generated by photoemission, back to the electrode. Re...

We synthesized the Cu(ii) and Zn(ii) complexes of the 2,7,12,17- tetrapropionic acid of 3,8,13,18-tetramethyl-21H,23H porphyrin (coproporphyrin-I) and successfully employed them as sensitizers in dye-sensitized solar cells. Copper(ii) coproporphyrin-I exhibits a power conversion efficiency of 3.8% measured under irradiation of AM 1.5G full sunlight (100 mW cm-2). © The Royal Society of Chemistry 2010.

The electrochemical behavior of 1-[(2S)-3-mercapto-2-methyl-1-oxopropyl]-L-Proline (Captopril) was studied by cyclic voltammetry (CV). The influence of pH on the diffusion waves and the parameters associated with them were studied. The diffusion waves exhibit a quasi-reversible mechanism at low pH (under pH = 6.5) and an irreversible electron transfer at higher pH values. Product adsorption waves (prepeaks) showing marked reversible behavior were observed and studied only at a pH of 2.20. Various parameters such as electron transfer rate (Ksh), maximum surface excess concentration (Γt), electron transfer coefficient (α), Frumkin's interaction parameter, (g) and diffusion coefficient (Dr) were calculated.

This study reports the results of the chemical analysis of the Longissimus thoracis and lumborum taken from 20 llama males, reared in the Andean highlands. The animals were slaughtered at 25 months and had a mean final body weight of 63 kg. Llama meat shows a low fat (3.51%) and cholesterol content (56.29 mg/100 g). The fatty acid composition in llama meat contains 50.34% saturated fatty acids, 42.48% monounsaturated fatty acids and 7.18% polyunsaturated fatty acids. Llama meat appears to be a healthy alternative red meat choice.

To assess the role of the container material on the quality of olive oil, 16 samples of selected extra-virgin olive oils (obtained in dark-green glass bottles as soon as they were produced) were stored in colorless polyethylene terephthalate (PET) bottles and in dark-green glass bottles for 2 months. For the very first time, room temperature and daylight storage were used to mimic the actual household storage conditions. Results clearly indicate that peroxide value increases rapidly above the threshold value; there was also an increase of free fatty acids and acidity and strong sensory quality loss upon storage in PET bottles. Influences of the technological operation adopted during oil extraction are discussed.

The fractional charge approach to Ion‐interaction chromatography (IIC) of zwitterions was used to quantitatively explain their retention behavior as a function of the Ion Interaction Reagent (H) concentration in the stationary phase and also to account for the influence of the zwitterion ionization degree, according to the mobile phase pH. The theory was validated using two Hs and two reversed phase columns. The good predictive abilities of the retention equations lend strong support to the hypotheses made by the fractional charge approach in the IIC of zwitterions. For the investigated homologous series the increase in retention upon H addition can be quantitatively related to the estimated fractional charge. The estimates of the operative charges and bonded phase coverages are very reasonable since they make sense physically. This way, they offer a cross validation of the fractional charge approach, since they compare well with those obtained from the fitting of parallel retention data, obtaine...

The influence of organic modifier and ion interaction reagent (IIR) concentrations on analyte retention in ion interaction chromatography (IIC) was investigated via a bivariate approach. The system examined is as follows: ODS-Hypersils was used as stationary phase; the eluent was a variable mixture of a phosphate buffer pH 2.1 and methanol ranging 0%–40% (v/v). The organic modifier decreases both the analyte and the IIR free energy of adsorption hence their interaction is lower when the organic modifier concentration is higher. Retention equations describe how these two factors interact with each another. The estimated equilibrium constant for the IIR adsorption corresponds to ΔG° = −17.3 KJ mol−1. This value is reliable because it makes sense physically. The chi-squared ∑(k calc − k exp)2 is 1.11E + 00 and 2.85E-02, for octopamine and 2-naphthalenesulfonate, respectively. Retention equations were compared with those obtained from the outstanding retention models in IIC. For the modelled system, the extended thermodynamic approach is able to explain experimental evidence that cannot be rationalised by existing retention models: it proves superior for fitting experimental data and is also able to predict when the purely electrostatic approach may work properly. In the absence of IIR the present retention equation reduces, as expected, to the relationship that describes the influence of organic modifier on retention behaviour in reversed-phase liquid chromatography.

Analysis of melanins and melanosomes in eight hair and skin samples taken of adult pigmented Argentine llamas (Lama glama L.) has been carried out. In each sample, eumelanins, pheomelanins and alkali-soluble melanins were identified. The total amount of melanins and the amount of eumelanins both decreased from black to reddish brown colour, while pheomelanins were found to be present in small quantities in each sample. Eumelanosomes were round and oval-shaped, displaying transverse striations clearly visible at low magnification. Dark brown samples revealed all four melanosomes stages. Stages I and II melanosomes appeared as large, asymmetrical vacuoles containing numerous microvesicles randomly scattered within an amorphous proteinaceous material (vesiculo-globular bodies). Stage III melanosomes had microgranular melanin deposits in the microvesicles and in the matrix. The fully melanized melanosomes (stage IV) were primarily round-shaped, showing an irregular outline and the electron-dense pigment was arranged to form large clusters. In light brown melanocytes, numerous melanosomes at different maturation stages could be found. Premelanosomes appeared ovoid, containing amorphous proteinaceous material and spotty and microgranular deposits. Mature melanosomes were fully melanized, homogeneously electron-dense, ovoid granules.

Recent breakthroughs in the theory of ion interaction chromatography (IIC) permit new analyses of the dependence of retention on different interdependent factors. The influence of the ionic strength / on the surface potential, the Donnan effect, and salting effects are taken into account to model the chromatographic behaviour of charged analytes in IIC. The most reliable experimental results found in the literature were used to test the retention equations that were developed following both a monovariate (/ changes as the concentration of H, ion interaction reagent, changes) and a bivariate (/ changes because of the simultaneous variation of H and of the background electrolyte concentrations) approach. The present extended thermodynamic model builds on the sound intuition of the electrostatic approach and proves to provide the most successful and exhaustive quantitative explanation of experimental evidence. It is also able to rationalise the less extensive agreement between the pure electrostatic approach predictions and experimental results. The adequacy of the model is supported by physically reliable estimates of the adjustable constant (ion-pair constants, deltaG degrees). Moreover statistical practice demonstrates that all the adjustable parameters (three at most) are statistically significant. A linear, zero crossing function with unit slope is obtained when k(pred) is plotted against k(exp). The mean percent error between k(pred) and k(exp) is 4.5% at most. In the absence of H the present retention equation reduces, as expected, to the relationship that describes the influence of / on the retention behaviour in reversed-phase liquid chromatography.

The chromatographic behaviour of charged analytes in ion interaction chromatography (IIC) has been investigated theoretically. A potential approximation for high surface potential was used to obtain simplified retention equations that are able to model analyte retention as a function of both the mobile and stationary phase concentrations of the ion-interaction reagent (IIR). The main advantage of using this potential approximation is that it allows calculation of the surface potential, without needing detailed information on physical and chemical properties of the mobile phase.

The chromatographic behaviour of charged analytes in Ion Interaction Chromatography (IIC) was theoretically investigated. Simplified retention equations were obtained via the linearized potential expression. They can be used to model analyte retention as a function of both the mobile and stationary phase concentration of the Ion-Interaction reagent (IIR), if the surface potential is below 25 mV. Simplified retention equations were compared to those, which can be obtained from two of the most important retention models in IIC. They reduce to stoichiometric or electrostatic retention model equations if the surface potential or pairing equilibria are respectively neglected.

The chromatographic behavior of charged analytes in ion interaction chromatography (IIC) is theoretically investigated. The chemical modifications of the stationary and mobile phases in the presence of ion interaction reagent (IIR) are theoretically shown to change the partition coefficient for charged molecules. The most reliable literature experimental results concerning retention behavior of charged molecules in IIC were used to test the new theory. Retention equations are compared with those that can be obtained from the most important retention models in IIC. The present exhaustive retention model, which is well-founded in physical chemistry, goes further than the previous ones whose retention equations can be viewed as limiting cases of the present theory. The present extended thermodynamic approach reduces to stoichiometric or electrostatic retention models if the surface potential or pairing equilibria are respectively neglected. Moreover, it is able to quantitatively explain experimental evidences that cannot be rationalized by the existing retention models.

The electrochemical reactions of dipicolinic acid (pyridine-2,6-dicarboxylic acid, DPA) in acidic and neutral solutions have been studied in order to determine the global electrochemical process. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate its behaviour in aqueous solution and clarify many unknown aspects of the reduction mechanism. A general scheme, in accordance with Laviron's theories, was proposed to explain the DPA electrochemical pathway, and the thermodynamic adsorption constant, K ads , was evaluated.

This communication suggests how the S/N ratio in the electrochemical determination of Captopril in urine samples can be simply improved. The proposed method involves unselective degradation of the proteins present in urine samples by refrigerating them down to −196°C. The separation is accomplished via ultracentrifugation at room temperature in such a way that very little manipulation of the sample occurs. This physical method is a useful tool for reducing background noise due to adsorbable products and for handling the sample as little as possible.

This paper clarifies the adsorption mechanism of 1-[(2S)-3-mercapto-2-methyl-1-oxopropyl]-L-proline (CPT) on DME. Some characteristic features of CPT adsorption, previously followed by cyclic voltammetry (CV), have been investigated to give more precise information about some electrochemical constants by alternating current polarography (ACP). The first harmonic ACP was considered a suitable tool for obtaining electrochemical parameters of surface-confined reactions. The entity and sign of the molecular interaction parameter (g), the thermodynamic constant of adsorption (Kads), the extrapolated apparent electron rate constant (Kextsh), the saturation concentration (Co), maximum surface density (Γt)etc. have been determined. The values of some of these electrochemical parameters, found in a previous paper, were confirmed.

The chromatographic behavior of zwitterions in ion-interaction chromatography (IIC) was investigated theoretically, on the basis of the following picture of the retention mechanism. The zwitterionic analyte is considered to interact with the charged stationary phase via an effective fractional charge, opposite to the surface one. Adsorption competitions between analytes and the ion interaction reagent (H) concur to explain the retention factor of zwitterions. The present model is quantitatively able to explain the retention behavior of zwitterions in IIC and also to account for the influence of the zwitterion ionization degree, according to the mobile phase pH, on the course of retention as a function of the H concentration. The approach we used is simple and epistemologically interesting because the retention equation for zwitterions may also be obtained from the general retention equation of our extended thermodynamic approach to IIC. Estimated magnitudes of the effective charges are very reasonable and show the same trend as that of the molecular dipole moments, as expected; the total ligand concentration compares well with the bonded phase coverage of the two columns used. For the homologous series from 4-aminobutyric-, to 8-aminocaprylic acid, the estimated effective charge always increases with increasing chain length and this results in parallel growth of the analyte retention increase upon H addition, so that the retention increase for the highest member of the series compares with that of a positively charged analyte. The estimated dipole for this analyte compares excellently to the estimate obtained via a quantum mechanics calculation. The influence of the mobile phase pH on retention was taken into account for the very first time. The good predictive abilities of the retention equations, and the reliability of the estimated constants that make sense physically confirm that retention modeling is able, at the thermodynamic level, to disclose the complexity of the IIC system.

New photosensitive materials can be obtained by electrochemical oxidation of thiocyanate and selenocyanate salts. Using (K,Na)SCN eutectic melt, the formation of an electrodic deposit, with photoelectrochemical properties, has already been reported by us. To improve the photoelectrochemical characteristics of the deposit, futher investigations were carried out in the following sistems: selenocyanate ammoniate, KSCH-Acetamide eutectic mixture and KSCN ethylene carbonate solution:. Attempts to obtain a massive deposit in the ammoniate solution were unsuccessful due to ammonia oxidation. Measurements performed on the other KSCN systems show that temperature is a parameter of remarkable importance. In fact, lowering the temperature one obtains a decrease on formation of parathiocyanogen on behalf of the polytrithiocyanogen, the species that gives rise to the photoeffect.

Sulphur and sulphide ions react in (K,Na)SCN eutectic melt with the formation of polysulphide. The electrolytic oxidation of SCN(-) at 155 degrees forms S(4) which gives S(2-)(5) with S(2-); at 165 degrees the sulphur electrogenerated is S(2) that reacts according to S(2) + S(2-) = S(2-)(3). The equilibrium constants of these reactions have been obtained by voltammetric measurements. The formation of S(2) at 155 degrees by irradiation from a xenon lamp was confirmed. The S(2) reacts with S(2-) to give S(2-)(3), and the equilibrium constant for this reaction is the same as that found for the reaction at 165 degrees .

Summary The electrodic oxidation of thiocyanate melt with different platinum electrodes giving different products is discussed. The formation of (SCN)3− species and the complicated electrodic reduction is reported. The cyclic voltammetry study of sulphide gives evidence of a coupled electrodic reaction at 155 and 165°C. The behaviour of the polysulphide has been studied by means of the same technique at 155°C.

Titrations of silver by chloride, bromide and iodide ions are carried out on molten acetamide solvent at temperature of 87°C; by these data the solubility products of silver halides have been computed. The presence of the complex species AgI, AgI2− and AgI32− has been found in the reaction between silver and iodide; the relative complexation constants have been calculated by graphical and numerical methods.

The electrochemical oxidation of selenocyanate in ammoniate solution was studied by potentiostatic, voltammetric, and galvanostatic measurements on Pt electrodes. The formation of both an anodic deposit, possibly a (SeCN) x matrix with trapped (SeCN) − 3 , and a soluble species, (SeCN) − 3 , was observed at current densities below 0.3 mA cm −2 . At higher current densities only deposit formation was observed. A theoretical treatment and experimental evidence are given for the kinetic mechanism of deposit formation. The mechanism explains the impossibility experienced in both obtaining a massive deposit and enhancing its photoelectrochemical properties.

Summary The solubility and the electrochemical behaviour of water at bright platinum microelectrodes have been studied in (Na,K) acetates (46.3 mol % CH3COONa) eutectic melt in the temperature range 250–290°C. The Henry's law constant has been found to be K=1.21×10−3 mol kg−1 Torr−1 at 250°C while the enthalpy of the process is −10.2±0.3 kcal mol−1. The water reduction (H2O+ea1/2H2+OH−) has been found to be a diffusion controlled process proceeding reversibly at bright platinum electrodes. By means of chronopotentiometry the water diffusion coefficient is DH2O=1.34×10−5 cm2 s−1 at 250°C while the Arrhenius activation energy for diffusion is +9.5±0.5 kcal mol−1.

Nitrite is converted completely to nitrogen by sulfamic acid, the excess of which is determined after conversion to ammonia by acid hydrolysis. Equal aliquots of sample are treated with increasing amounts of sulfamic acid, and potentials are measured after the hydrolysis. Nitrite in the range 1.5 × 10 -5 –2 × 10 -2 mol l -1 can be determined with errors less than 2%.

The voltammetric behavior of Pb(II), Cd(II), Tl(I) and Ni(II) in fused acetamide at 87°Chas been studied. The measurements have been carried out using normal polarography and cyclic voltammetry either with mercury or platinum electrodes. Only Tl(I) reduction occurs reversibly while all the other cations show some degree of irreversibility.

A voltammetric method for the determination of 3-mercapto-D-2-methylpropanoyl-L-proline, a hypotensive drug whose pharmaceutical name is Captopril (CPT), in the concentration range from 9.0×10 −10 M to 3×10 −6 M , is described. In this range the peak current increases linearly with drug concentration even when different collection periods are used. A self-cleaning Hanging Mercury Drop Electrode (HMDE) was used and a negative Differential Pulse potential (DP) was applied to the indicator electrode. The stripping peak of CPT splits into two peaks as soon as the concentration is increased over about 10 −5 M ; in the oxidation DP scan, instead, this splitting is observed at a concentration of 2.0×10 −4 M . Some attempts were made to verify the suitability of other techniques such as Alternating Current polarography (AC) and the use of a different electrode, the Wax-Impregnated Graphite Electrode (WIGE).

The feasibility of the titration of some cations in molten sodium thiocyanate-potassium thiocyanate mixture with electrolytically generated sulphide ions has been tested at 443 K. Quantitative data are given for the titration of cadmium, mercury and zinc ions.

Summary Potentiometric and biamperometric titrations of halide and silver ions have been carried out in molten hydrated sodium acetate at 360 K. Halide and silver ions were generated coulometrically. The titration error was always less than 2%. The solubility products of the silver halides were determined from the potentiometric data.

The anodic deposit on platinum electrodes in thiocyanate melts is a complex mixture of species which, depending on experimental conditions, undergoes various chemical reactions terminated by complete polymerisation.