Annali di chimica最新文献

2-Hydroxy-3-methoxy benzaldehyde thiosemicarbazone (HMBATSC) has been synthesized and its analytical applications are investigated. A rapid, simple, sensitive and selective spectrophotometric method is developed for the determination of palladium (II) in aqueous dimethyl formamide (DMF). Palladium (II) forms a yellowish M₂L₃ complex with 2-hydroxy-3-methoxy-benzaldehyde green coloured thiosemicarbazone in the pH range 1.0-7.0 at room temperature. The complex shows absorption maximum at 380nm with molar absorptivity and Sandell's sensitivity of 2.198 × 10⁴ l mol^-1 cm^-1 and 0.049μg cm^-2 respectively. Beer's law is obeyed in the range of 0.426 to 4.257 μg ml^-1 of Pd (II). A second order derivative spectrophotometric ethod for the determination of palladium (II) has also been proposed. Interference of various diverse ions has been studied. The proposed method is successfully applied for the determination of palladium in alloy steels and in hydrogenation catalysts.

A highly sensitive solid phase microextraction – high performance liquid chromatographic method has been developed for the determination of copper(II) using morpholine-4-carbodithioate (MDTC) as an analytical reagent. The MDTC formed yellowish- brown species of copper(II) at a pH range of 2-9 and complex was sorbed onto PDMS fiber. The Cu(II)-MDTC complex shows maximum absorbance at 430 nm and can be separated on C18 column by using acetonitrile : water (80 : 20) at a flow rate of 1.0 ml min^-1.The detection limit of method was found to be 0.51 μg L^-1. The interference due to common metal ions were studied. The repeatability of the method was checked by finding the relative standard deviation. The developed method was successfully employed for the determination of copper(II) in different alloy samples and the results were compared with existing methods.

Simple and novel spectrophotometric method is described for simultaneous determination of aluminum and iron. The method is based on the colored complexes formed by aluminum and iron with hematoxylin in the presence of cetyltrimethylammonium bromide as a surfactant at pH 5.8. All factors affecting the sensitivity were optimized and the linear dynamic range for determination of aluminum and iron was found. The simultaneous determination of aluminum and iron mixtures by using spectrophotometric methods is a difficult problem, due to spectral interferences. By multivariate calibration methods such as partial least squares (PLS), it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction (OSC) is a preprocessing technique used for removing the unrelated information and is a suitable preprocessing method for PLS calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 360-620 nm range for 25 different mixtures of aluminum and iron. Calibration matrices contained 0.06-21.00 and 0.03-15.00 μg mL^-1 of aluminum and iron, respectively. The RMSEP for aluminum and iron with OSC and without OSC were 0.06, 0.08 and 0.24, 0.27, respectively. The proposed method has been applied to the simultaneous determination of aluminum and iron in plant and water samples.

A sensitive, simple and rapid spectrophotometric method for the determination of mercury (II) based on its catalytic effect on the abstraction of coordinated cyanide from hexacyanoferrate (II) by pyrazine has been developed using fixed time procedure. The extent of the reaction is monitored spectrophotometrically by measuring the increase in absorbance at λ_max=440 nm of the yellow colored complex, [Fe(CN)₅Pz]³⁻ under the reaction conditions; [Fe(CN)₆]⁴⁻=7.2×10⁻³ mol L⁻¹, [P_z]=3.75×10⁻⁴ mol L⁻¹, temperature=25.0±0.1 °C, pH= 2.50±0.02 and I=0.1 mol L⁻¹(KNO₃). The experimental rate data under the conditions used in the present study exhibited a linear dependence between absorbance and [Hg²⁺] catalyst in the range 5.065–50.15 ng mL⁻¹. The detection limit is found to be 4.01 ng mL⁻¹. The maximum relative standard deviations and percentage errors for mercury(II) determination are found to be 2.2 and 3 % respectively. The percentage recoveries are found to be in the range of 99–102 %. Analytical data fordetermination of mercury(II) is presented together with the application of proposed method in water spiked synthetic mixtures. The validity of the proposed method is tested by comparing the results obtained by present method with atomic absorption spectrometry.

A potentiometric thiocyanate-selective sensor based on copper(II) bis(benzoylacetone)propylenediimine complex as a new neutral carrier for a thiocyanate-selective electrode is reported. The response mechanism is discussed in view of the UV spectroscopy technique. The sensor displays a near Nernestian slope of -57.4 ± 0.5 mV per decade. The working concentration range of the electrode is 8.0×10^-7-1.0×10^-1 M with a detection limit of 7.4×10^-7 M. The response time of the sensor in the all concentration ranges is very short (5-10 s). The response of the sensor is independent of pH, in the pH range of 1.7–11.5. The best performance was obtained with a membrane composition of 32.69 % PVC, 57.34 % dibutyl phthalate, 6.82 % complex and 3.15 % methyltrioctylammonium chloride (MTOAC) as additive. The proposed electrode is more selective than other proposed methods for determination of thiocyanate ion over a wide variety of common inorganic and organic anions and it was successfully applied to direct determination of thiocyanate in the presence of other anions in biological, water and waste water samples.

A poly(calconcarboxylic acid) film was prepared originally via electrochemically depositing calconcarboxylic acid (CCA) on a glassy carbon electrode (GCE) by cyclic voltammetry (CV). The polymer showed excellent electrocatalytic activity to the oxidation of norepinephrine and could detect separately ascorbic acid (AA), norepinephrine (NE) and uric acid (UA) in their mixture. Separations of the oxidation peak potentials of NE-AA and UA-AA were 160 and 150 mV, respectively. Using differential pulse voltammetry (DPV), the peak current of NE was linearly dependent on its concentration within the range of 10–300 μmol L^-1. No interference was produced for the determination of NE in the presence of AA and UA. Owing to its good selectivity and robustness, the poly(CCA)-modified GCE was used for the determination of NE in injections with satisfactory results.

Measurements of gaseous organic compounds were carried out near Ny-Alesund, in the Norwegian Arctic, during September 2004. Twenty alkanes, alkenes and aromatic hydrocarbons from ethane to toluene and six aldehydes and ketones from formaldehyde to butanal, were identified and quantified in air samples. Hydrocarbons showed a quite uniform distribution, with ethane being by far the most abundant component (>1 ppb), followed by propane (>0.4 ppb) and butanes (>0.3 ppb), while for unsaturated homologues, except ethene, concentrations never exceeding 0.05 ppb were observed. This distribution confirmed that hydrocarbon depletion during the transport time from Europe into the Arctic was depending upon their atmospheric lifetimes, calculated relatively to the OH reactivity scale. The presence of short lived hydrocarbons could be associated to local sources of anthropogenic and/or biogenic origin. Although the local air photochemistry played a primary role in the production of lower aldehydes in late summer, the observed mixing ratios of formaldehyde (in the 0.25 – 0.50 ppb range) could not be fully explained by known gas-phase chemistry. In this case additional sources, such as fluxes of formaldehyde from snow pack to the atmosphere and/or local anthropogenic activities, were to be taken into consideration. The possible influences of these sources on HCHO mixing ratios were analysed by means of a backward-trajectory circulation model.