Novel solid-phase extraction and preconcentration technique coupled with ICP-AES for the determination of Cr(III), Ni(II), and Zn(II) in various water samples

Newly synthesized 2-propylpiperidine-1-carbodithioate (2-PPC) was used for the extraction of Cr(III), Ni(II), and Zn(II) from various water samples. In the present investigation, the use of a syringe loaded with sorbent for the separation and enrichment of Cr(III), Ni(II), and Zn(II) prior to their determination by inductively coupled plasma-atomic emission spectrometry (ICP-AES) was proposed to substitute the batch and column techniques. The described method was compared with the column technique with respect to fastness, simplicity, recovery, and risk of contamination. The syringe was loaded with 1.0 g of sorbent in order to retain the analyte elements. Next, 7.0 mL of sample solution (pH 5.0 ± 0.2) was drawn into the syringe in 15 s and discharged over 15 s. Then, an eluent (3.0 M HCl) was drawn into the syringe and ejected back to desorb the analyte elements. At the optimum conditions, the percentage recoveries of Cr(III), Ni(II), and Zn(II) were in the range of 94.50 to 99.62% with a standard deviation (S.D.) of 0.03%. The elements could be concentrated by drawing and discharging several portions of sample successively and eluting only one time. The detailed study of various interferences proved the method to be highly selective. The risk of contamination is less than that with the column technique. The method was successfully applied to the determination of Cr(III), Ni(II), and Zn(II) in spiked and natural water samples. The results obtained are in good agreement with those obtained by the reported methods at the 95% confidence level. The text was submitted by the authors in English.     

Cyclic voltammetric studies on gallium film electrodes in alkaline media

Using cyclic voltammetric techniques the electrochemical behaviour of gallium in alkali media has been investigated. Three anodic peaks, one cathodic peak, and a secondary anodic peak—an observation hitherto unreported—are obtained. Detailed analyses of these various stages of oxidation and reduction based on their peak potential and peak current characteristics have revealed the nature of the underlying electrochemical reactions.     

Turbulent time-events in channel with rough walls

This brief communication quantifies the time-events that contribute to the dynamics of wall-bounded flows with rough walls. Lumley’s Proper Orthogonal Decomposition (POD) methodology has been used to extract the energetic modes of the flow. We have used the concept of entropy, a representation of lack of organization in the flow, to represent the extent of spread of turbulent kinetic energy to higher modes. The rough-wall dynamics is dominated by fast activity (short time period) propagating modes and slow activity (long time period) roll modes. A single dominant timescale has been captured for all the propagating modes in flows over smooth walls; multiple dominant timescales representing various vortex shedding events are captured for rough walls. Variable-interval time averaging technique has been used to obtain the bursting frequency. The bursting frequency of rough-wall turbulence is higher compared to smooth-wall turbulence, suggesting that roughness enhances turbulence production activity. Another insightful observation for rough walls revealed by our study is that the vortex shedding frequency of roughness elements is much higher compared to the bursting frequency of rough-wall turbulence. POD provides a straightforward method to extract the natural frequency of shed vortices due to roughness, an important dynamical activity in rough-wall turbulent boundary layers.     

Coherent States and Modified de Broglie-Bohm Complex Quantum Trajectories

This paper examines the nature of classical correspondence in the case of coherent states at the level of quantum trajectories. We first show that for a harmonic oscillator, the coherent state complex quantum trajectories and the complex classical trajectories are identical to each other. This congruence in the complex plane, not restricted to high quantum numbers alone, illustrates that the harmonic oscillator in a coherent state executes classical motion. The quantum trajectories we consider are those conceived in a modified de Broglie-Bohm scheme. Though quantum trajectory representations are widely discussed in recent years, identical classical and quantum trajectories for coherent states are obtained only in the present approach. We may note that this result for standard harmonic oscillator coherent states is not totally unexpected because of their holomorphic nature. The study is extended to coherent states of a particle in an infinite potential well and that in a symmetric Poschl-Teller potential by solving for the trajectories numerically. For the Gazeau-Klauder coherent state of the infinite potential well, almost identical classical and quantum trajectories are obtained whereas for the Poschl-Teller potential, though classical trajectories are not regained, a periodic motion results as t→∞. Similar features were found for the SUSY quantum mechanics-based coherent states of the Poschl-Teller potential too, but this time the pattern of complex trajectories is quite different from that of the previous case. Thus we find that the method is a potential tool in analyzing the properties of generalized coherent states.     

Determination of rhodium in water samples using cloud point extraction (CPE) coupled with flame atomic absorption spectrometry (FAAS)

Cloud point extraction was applied as a method for preconcentration of rhodium after formation of a complex with 2-propylpiperidine-1-carbodithioate (2-PPC), and later determined by flame atomic absorption spectrometry using TritonX-114 as surfactant. Rhodium was complexed with 2-PPC in an aqueous phase and kept for 15 min in a thermostatted bath at 40 °C. Separation of the two phases was accomplished by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud point extraction were optimized and successfully applied to rhodium determination in various water samples. Under optimized conditions, the preconcentration system (100 mL sample) permitted an enhancement factor of 50. The detection limits obtained under optimal conditions was 0.052 ng mL⁻¹. The extraction efficiency was investigated at different rhodium concentrations (7.0–42.0 μg mL⁻¹), and good recoveries (96.42–99.14%) were obtained using this method. It has been applied to the determination of rhodium in water and was compared with reported methods in terms of Student’s ‘t’-test and variance ratio ‘f’-test.     

Oxidation of L-lysine by diperiodatocuprate (III) in aqueous alkaline medium by the stopped flow technique

The kinetics of oxidation of L-lysine by diperiodatocuprate (III) (DPC) in alkaline medium at a constant ionic strength of 0.15 mol/dm³ was studied spectrophotometrically. The reaction between DPC and L-lysine in an alkaline medium had a 1: 2 stoichiometry (L-lysine: DPC). The reaction was first order in [DPC] and less than first order in [L-lysine] and [alkali]. The addition of periodate had no effect on the rate of the reaction. The intervention of free radicals was observed in the reaction. The oxidation reaction in alkaline medium was shown to proceed via a DPC-L-lysine complex. The main products were identified by spot test and spectral studies. The reaction constants involved in different steps of the mechanism were calculated. The activation parameters with respect to the slow step of the mechanism were computed and discussed, and thermodynamic values were also determined. The article is published in the original.     

Temperature-dependent photoelectron spectroscopy of methyl benzoate anions: observation of steric effect in o-methyl benzoate

Temperature-dependent photoelectron spectra of benzoate anion (C6H5CO2(-)) and its three methyl-substituted isomers (o-, m-, p-CH3C6H4CO2(-)) have been obtained using a newly developed low-temperature photoelectron spectroscopy apparatus that features an electrospray source and a cryogenically controlled ion trap. Detachment channels due to removing electrons from the carboxylate group and benzene ring pi electrons were distinctly observed. Well-resolved vibrational structures were obtained in the lower binding energy region due to the OCO bending modes, except for o-CH3C6H4CO2(-), which yielded broad spectra even at the lowest ion trap temperature (18 K). Theoretical calculations revealed a large geometry change in the OCO angles between the anion and neutral ground states, consistent with the broad ground-state bands observed for all species. A strong steric effect was observed between the carboxylate and the methyl group in o-CH3C6H4CO2(-), such that the -CO2(-) group is pushed out of the plane of the benzene ring by approximately 25 degrees and its internal rotational barrier is significantly reduced. The low rotational barrier in o-CH3C6H4CO2(-), which makes it very difficult to be cooled vibrationally, and the strong coupling between the OCO bending and CO2 torsional modes yielded the broad PES spectra for this isomer. It is shown that there is no C-H...O hydrogen bond in o-CH3C6H4CO2(-), and the interaction between the carboxylate and methyl groups in this anion is found to be repulsive in nature.     

Excess volumes of ternary mixtures of N,N-dimethylformamide-diethyl ketone-1-alkanols at 303.15K

Volume changes on mixing of ternary liquid mixtures of N,N-dimethylformamide and diethyl ketone with 1-alkanols have been measured as a function of composition at 303.15 K. The alkanols include 1-propanol, 1-butanol, 1-pentanol and 1-hexanol. The measured V^E values are negative in the mixtures of N,N-dimethylformamide, diethyl ketone and 1-propanol, or 1-butanol. The V^E data exhibits an inversion in sign in the mixture containing 1-pentanol and positive excess volumes are observed in the mixture containing 1-hexanol. The measured data are compared with predicted values based upon empirical relations. The excess volume for the binary mixture of N,N-dimethylformamide with diethyl ketone has been measured over the entire range of composition at 303.15 K. The V^E values are negative for the binary mixture.     

Influence of optical constants in carbon-based dispersions for enhanced solar evaporation

Journal of Thermal Analysis and Calorimetry - Carbon-based nano- and microfluid dispersions show promise as effective media for solar-assisted desalination. They act as strong solar absorbers in...