Optimization of a HPLC procedure for simultaneous determination of cisplatin and the complex cis,cis,trans-diamminedichlorodihydroxoplatinum(IV) in aqueous solutions

A RP-HPLC procedure for the simultaneous determination of cisplatin and the complex cis,cis,trans-diamminedichlorodihydroxo-platinum(IV), was development. The developed procedure was validated in terms of linearity, accuracy, precision, limits of detection (LOD), limits of quantification (LOQ) and specificity. The limits of detection (LOD) were 0.47 x 10-4 and 0.53 x 10-4 mol L-1 and the limits of quantification (LOQ) were 1.57 x 10-4 and 1.75 x 10-4 mol L-1, for cisplatin and cis,cis,trans-diamminedichlorodihydroxopla-tinum(IV), respectively. The average recoveries of cisplatin and cis,cis,trans-diamminedichlorodihydroxoplatinum(IV) was 100.6% ± 1.4 and 101.2% ± 1.1, respectively. Intermediate (inter-day) precision, repeatability and specificity of the procedure for hydrolysis products of cisplatin were studied. The results of the study showed that the proposed RP-HPLC procedure is simple, rapid, precise, accurate and specific.

Copper electrodeposition on glassy carbon and highly oriented pyrolytic graphite substrates from perchlorate solutions

In present work, we analyzed the copper electrodeposition onto GCE (System I) and HOPGE (System II) from perchlorate solutions. The current density transients obtained from system I and II were well described through a kinetic mechanism that involves four different contributions: (a) a Langmuir type adsorption process, b) an electron transfer from Cu2+→Cu+, (c) a 3D nucleation limited by a mass transfer reaction and (d) a proton reduction process. It was observed that the values of the nucleation rate, the number of active nucleation sites were increased with the overpotential and they are bigger onto GCE in comparison with HOPGE.

Monitoring of praseodymium(III) ions in aqueous solutions, soil and sediment samples by a PVC membrane sensor based on a furan-triazole derivative

A furan-triazole derivative has been explored as an ionophore for preparation of a highly selective Pr(III) membrane sensor. The proposed sensor exhibits a Nernstian response for Pr(III) activity over a wide concentration range with a detection limit of 5.2×10-8 M. Its response is independent of pH of the solution in the range 3.0-8.8 and offers the advantages of fast response time. To investigate the analytical applicability of the sensor, it was applied successfully as an indicator electrode in potentiometric titration of Pr(III) solution and also in the direct and indirect determination of trace Pr(III) ions in some samples.

Time-series forecasting of pollutant concentration levels using particle swarm optimization and artificial neural networks

This study evaluates the application of an intelligent hybrid system for time-series forecasting of atmospheric pollutant concentration levels. The proposed method consists of an artificial neural network combined with a particle swarm optimization algorithm. The method not only searches relevant time lags for the correct characterization of the time series, but also determines the best neural network architecture. An experimental analysis is performed using four real time series and the results are shown in terms of six performance measures. The experimental results demonstrate that the proposed methodology achieves a fair prediction of the presented pollutant time series by using compact networks.

Kinetic modeling of the biosorption of Cd2+ ions from aqueous solutions onto Eichhornia crassipes roots using potentiometry: low-cost alternative to conventional methods

This work presents the use of potentiometric measurements for kinetic studies of biosorption of Cd2+ ions from aqueous solutions on Eichhornia crassipes roots. The open circuit potential of the Cd/Cd2+ electrode of the first kind was measured during the bioadsorption process. The amount of Cd2+ ions accumulated was determined in real time. The data were fit to different models, with the pseudo-second-order model proving to be the best in describing the data. The advantages and limitations of the methodology proposed relative to the traditional method are discussed.

Preparation and evaluation of magnetic chitosan particles modified with ethylenediamine and Fe(III) for the removal of Cr(VI) from aqueous solutions

The adsorption of Cr(VI) in aqueous solution by magnetic particles of crosslinked chitosan-ethylenediamine-Fe(III) (MPCh-EDA-FeCL) was studied in a batch system. Fe3+ in the MPCh-EDA-FeCL permitted that adsorption of Cr(VI) occurred with maximum efficiency between pH 3 and 11. The maximum adsorption capacity at pH 7.0 was 81.04 mg g-1 at 25 ºC. The adsorption kinetic process was described by the pseudo-second-order model. Thermodynamic parameters indicated spontaneous, exothermic and chemical adsorption nature. The adsorbent was successively regenerated using a 0.1 mol L-1 NaOH solution. Results were satisfactory for treatment of wastewater from the electroplating industry.

ANION-BINDING AND SENSING PROPERTIES OF NOVEL RECEPTORS BASED ON N-(INDOL-3-YLGLYOXYLYL)BENZYLAMINE

Indole-based receptors such as biindole, carbazole, and indolocarbazole are regarded as some of the most favorable anion receptors in molecular recognition. This is because indole groups possess N–H groups as hydrogen-bonding donors. The introduction of amide groups in the indole framework can induce strong binding properties and good water solubility. In this study, we designed and synthesized a series of N-(indol-3-ylglyoxylyl)benzylamine derivatives as novel and simple anion receptors. The receptors derived by aryl and aliphatic amines can selectively recognize F– based on a color change from colorless-to-yellow in DMSO. The receptors derived by hydrazine hydrate can recognize F–, AcO–, and H2PO4– by similar color changes in DMSO and can even enable the selective recognition of F– in a DMSO–H2O binary solution by the naked eye. Spectrographic data indicate that complexes are formed between receptors and anions through multiple hydrogen-bonding interactions in dual solutions.

SYNTHESIS AND BIOLOGICAL ACTIVITY OF NEW SERIES OF ORGANOTIN(IV) ESTERS WITH N,N-DIACETYLGLYCINE

A bioactive N,N-diacetylglycine (NNDAG) and new organotin(IV) complexes (OTCs) (1-7) were synthesized. Spectroscopic techniques were employed to characterize NNDAG and OTCs. FTIR was employed to verify N,N protection of glycine by acetyl groups. The disappearance of υ(OH) at 3000-2600 cm-1 showed de-protonation of free ligand. The Δυ 150<200 cm-1 of OTCs 4-7 verified bidentate coordination with tetrahedral geometry. The Δυ of OTCs1 and 3 was <200 cm-1 exhibitingtrans -octahedral geometry while OTC 2 dimer was assigned a unique sinusoidal view. The 1H NMR spectra of OTCs verified their synthesis by de-protonation of NNDAG and no chemical shift was found downfield for carboxylic acid proton. The 13C, 119Sn NMR and Mass spectrometric data also supported FTIR and 1H NMR descriptions. The OTCs 4, 5, 6 and7 (500 ppm) proved twice as active against Escherichia coli as the standard antibiotic enoxacin (1000 ppm). The promising property of the OTCs (4, 5, 6 and7) is clearly due to their tetrahedral. The OTCs 4and 5 exhibited excellent activity against M. minimum and good activity against T. castaneum.LD50 of all the compounds were determined and OTCs4, 5 and 7 were found to be active.

Regime Switching Models for Electricity Time Series that Capture Fat Tailed Distributions

In the power market, electricity prices play an important role at the economic level. The behavior of a price trend usually known as a structural break may change over time in terms of its mean value, its volatility, or it may change for a period of time before reverting back to its original behavior or switching to another style of behavior, and the latter is typically termed a regime shift or regime switch. Our task in this thesis is to develop an electricity price time series model that captures fat tailed distributions which can explain this behavior and analyze it for better understanding. For NordPool data used, the obtained Markov Regime-Switching model operates on two regimes: regular and non-regular. Three criteria have been considered price difference criterion, capacity/flow difference criterion and spikes in Finland criterion. The suitability of GARCH modeling to simulate multi-regime modeling is also studied.

Analysis of Patterns in Electricity Spot Market Time Series

Due to its non-storability, electricity must be produced at the same time that it is consumed, as a result prices are determined on an hourly basis and thus analysis becomes more challenging. Moreover, the seasonal fluctuations in demand and supply lead to a seasonal behavior of electricity spot prices. The purpose of this thesis is to seek and remove all causal effects from electricity spot prices and remain with pure prices for modeling purposes. To achieve this we use Qlucore Omics Explorer (QOE) for the visualization and the exploration of the data set and Time Series Decomposition method to estimate and extract the deterministic components from the series. To obtain the target series we use regression based on the background variables (water reservoir and temperature). The result obtained is three price series (for Sweden, Norway and System prices) with no apparent pattern.

Thermal decomposition and stability in a series of heterobimetallic carbonyl compounds of the type [Fe(CO)4(HgX)2] (X=Cl, Br, I)

Heterobimetallic carbonyl compounds of the type [Fe(CO)4(HgX)2] (X= Cl, Br, I), which have metal-metal bonds, have been prepared in order to study their thermal stabilities as a function of the halogen coordinated to mercury atoms. The characterization of the above complexes was carried out by elemental analysis, IR and NMR spectroscopies. Their thermal behaviour has been investigated and the final product was identified by IR spectroscopy and by X-ray powder diffractogram.

About the kinetics and mechanism of the reactions of 4-(2-pyridylazo)-resorcinol, with Zn2+, Cu2+ and Zn2++Cu2+ equimolar mixtures, in aqueous solutions

The kinetics and mechanism of the reactions between 4(2pyridylazo)-resorcinol and Zn2+, Cu2+ and Zn2++Cu2+ equimolar mixtures were studied. The reactions were performed in aqueous solution (pH = 8.5, borate buffer) and monitored spectrophotometrically at 500 nm using stopped-flow technique. Spectral and kinetic data indicate that the Zn2++Cu2+ equimolar mixture behaves as an unique species and it can be attributed to the interactions of Zn2+ and of Cu2+ with water molecules in the aqueous solution. A mechanism is proposed and the rate constants are calculated.

A fluorescence probe study of gemini surfactants in aqueous solution: a comparison between n-2-n and n-6-n series of the alkanediyl-a,w-bis (dimethylalkylammonium bromides)

Two series of alkanediyl-a,w-bis (dimethylalkylammonium bromide (n-2-n and n-6-n; n=8, 10,12, and 16) have been synthesized and their micelles properties studied in aqueous solution using pyrene, pyrenecarboxaldehyde (PCA) and 1,8 anilinonaphtalene sulfonic acid sodium salt (ANS) as fluorescent probes. The micelles from these surfactants have been characterized on the basis of the information provided by micelle-solubilized fluorescent probes. The obtained results indicated that the surfactant concentration at which a marked decrease in l max parameter of pyrenecarboxaldehyde (PCA) occurs corresponds to the CMC determined by conductimetric measurements. Changes in the emission spectra of ANS and PCA observed in the submicellar range for both surfactants series (n-2-n and n-6-n) were interpreted as formation of pre-aggregates. It was found that the dimeric surfactants with long spacer (s= 6) form more hydrated aggregates when compared with those formed by the n-2-n and CnTAB surfactants series. This was attributed to a more difficult packing of n-6-n surfactant molecules to form micelles.

Bound state solutions of schrödinger equation for a more general exponential screened coulomb potential via Nikiforov-Uvarov method

The arbitrary angular momentum solutions of the Schrödinger equation for a diatomic molecule with the general exponential screened coulomb potential of the form V(r) = (- a / r){1+ (1+ b )e-2b } has been presented. The energy eigenvalues and the corresponding eigenfunctions are calculated analytically by the use of Nikiforov-Uvarov (NU) method which is related to the solutions in terms of Jacobi polynomials. The bounded state eigenvalues are calculated numerically for the 1s state of N2 CO and NO