Matrix Solid-Phase Dispersion Extraction and UPLC Determination of Sudan Dyes in Chili Powder

A new method involving matrix solid-phase dispersion (MSPD) extraction and UPLC in conjunction with photodiode array detection was developed for the rapid and simple determination of Sudan dyes in chili powder. Separation of Sudan I, Sudan II, Sudan III, and Sudan IV was achieved within 2 min on the 1.7 μm Acquity UPLC BEH C18 column by using gradient elution with a mobile phase consisting of acetonitrile–water at a flow rate of 0.5 mL min^?1. Optimization of MSPD extraction parameters, such as type of solid sorbent and elution solvent were carried out. Optimal conditions selected for MSPD extraction were 0.25 g of sample, 0.5 g of silica gel as solid sorbent, and 7 mL of acetonitrile–methanol (9:1, v/v) as eluting solvent. Limits of detection ranged between 0.25 and 0.30 mg kg^?1 depending on the dye involved. All analytes provided average recoveries from spiked (at 1, 1.5, and 2 mg kg^?1) chili powder samples ranging from 81 to 106%. The method was applied to the analysis of chili powder samples obtained from different countries.     

Ion-pair chromatographic monitoring of photographic effluents

Ion-pair chromatographic technique was developed for the rapid and simple determination of the main contaminants (bromide, iodide, sulphite, thiosulphate, thiocyanate, iron(III)-EDTA chelate, free EDTA, hydroquinone and phenidone) in spent photographic solutions. Free EDTA was converted into stable Ni(II)-EDTA chelate prior to analysis. The optimal mobile phase conditions were established by varying the concentrations of tetrabutylammonium (TBA) phosphate and acetonitrile, pH and ionic strength. Separation of five inorganic anions, two metal chelates and two neutral compounds was accomplished in about 30 min using a mobile phase containing 7.5 mmol/L TBA-phosphate, 10 mmol/L NaCl (pH 6.5) and 20% (v/v) acetonitrile. The detection limits (UV detection at 210 nm) ranged from 0.4 μmol/L for phenidone to 8 μmol/L for sulphite with a linearity of 2–2.5 orders of magnitude. The method was applied to the rapid monitoring of spent photographic solutions before and after decomposition. The recovery tests established for two samples were within the range 95–103%.      

Cu(II) Ion Complexation by Excess of β-cyclodextrin in Aqueous Alkaline Solutions

Polarographic investigations of Cu(II) complexation in aqueous alkaline solutions containing an excess of β-cyclodextrin (β-CD) show that the complex formation begins at pH > 11, the concentration of free (uncomplexed) Cu(II) ions being in the range from ca. 10^-12 to ca. 10^-19 M, depending on β-CD concentration and pH. The formation of copper(II) 1:1 hydroxy-complex with β-cyclodextrin anion (CD^2-) was observed at pH 11–14. The logarithm of the stability constant of CuCD(OH)^2- ₂ complex is 19.7 ± 0.2 (20 °C, ionic strength 1.0), the values of the molar extinction coefficient and of the diffusion coefficient of this complex are 50 M^-1 cm^-1 (λ_max = 660 nm) and 1.0 × 10^-6 cm² s^-1, respectively.     

Peculiarities of Electrochemical Bismuth Film Formation in the Presence of Bromide and Heavy Metal Ions

Bi films were deposited on glassy carbon electrode from solutions with and without KBr. The morphology of both types of the films was characterized by scanning electron microscopy (SEM), and their electrochemical behavior was studied by square wave (SWV) and cyclic voltammetry (CV). Bi films were also co‐deposited with common analyte‐heavy‐metals in the presence of KBr and these films also were characterized by SEM, SWV and CV in order to understand the formation of the mixed metal films. All films studied had a different morphology. Bromide addition made the Bi films more compact and uniform, whereas Pb catalyzed Bi film deposition.     

Aqueous sol–gel synthesis,thermoanalytical study and luminescent properties of M0.05Eu0.05Ca0.9MoO4 (M=Li,Na, K,Rb, Cs) nanocrystallites

Nano-sized M_0.05Eu_0.05Ca_0.9MoO₄ (M=Li, Na, K, Rb, Cs) ceramics have been successfully synthesized by an aqueous sol–gel synthesis method using a tartaric acid as a ligand. In order to reveal the influence of the peculiarities of the nature of dopants effect into the crystallization of CaMoO₄ double oxide, the thermal analysis of the as-prepared gels was performed. In addition, infrared spectroscopy was used in order to identify the functional groups from the characteristic stretching vibrations in the M–Eu–Ca–Mo–O tartrate gel precursors. Besides, to confirm the dynamics of growing crystallites in the final ceramics and to reveal the morphological changes on the surface, the x-ray diffraction and scanning electron microscopy were applied. Finally, photoluminescence measurements were used to estimate the optical properties of europium oxide as a dopant in the samples according to the nature of alkali metal. Therefore, according to the obtained results, it was estimated that luminescence intensity of Eu³⁺ ions is mainly affected by the chemical reaction, which takes place at about 973 K of temperature. This effect was partly confirmed from the results of the thermal decomposition of M–Eu–Ca–Mo–O tartrate gel precursors with an endothermic behaviour in the DSC curve, which indicates the crystallization mechanism of the CaMoO₄ double oxide.