X-ray investigation of the role of the mixed emulsifier in the structure formation in o/w creams

The aim of this research work was to clarify the role of the mixed emulsifier in the structure formation and water binding mode in the case of o/w creams prepared with different surfactants. The swelling behavior of mixed emulsifiers was examined by means of direct investigation methods such as transmission electron microscopy (TEM) and X-ray diffraction. The detailed structure image of the creams was created with the help of the latter. The influence of the structure of the hydrophilic gel phase, and the structural changes during storage were studied with rheological methods. On the basis of the results, it can be stated that the investigated creams had different structures from those mentioned in the literature: surfactant did not create a mixed bilayer with the structure to furnish fatty amphiphile; instead, micelles were formed. These results correlated well with the results of the rheological tests.     

Simultaneous determination of Cd(II), Cu(II) and Pb(II) in surface waters by solid phase extraction and flow injection analysis with spectrophotometric detection

A method for heavy metal monitoring using spectrophotometric detection is presented. Traces of Cu(II), Pb(II) and Cd(II) at the low microg l(-1) level can be determined simultaneously after both selective removal of metal interferences and preconcentration using 'extraction chromatographic resins'. Lewatit TP807'84, which contains di(2,4,4-trimethylpentyl)phosphinic acid as active component, was used as solid adsorbent. Two minicolumns containing this resin were used: one at pH 3.2 for the removal of interferences, such as Zn(II) and Fe(III), and the other at pH 5.5 for the selective preconcentration of the target analytes. Spectrophotometric determination used FIA methodology with sulfarsazene as chromogenic reagent and partial least-squares multivariate calibration. The method was successfully applied to the analysis of surface waters from the Llobregat river and ground water samples from wells in the Guadiamar basin. Accuracy, expressed in terms of recoveries, was in the range 80-120% and relative standard deviations were below 10%.     

Determination of the Lipophilicity of Xanthines by Reversed-Phase Liquid Chromatography

JPC – Journal of Planar Chromatography – Modern TLC -     

Molecular structure of 4,4′-sulfandiyl-bis-thiophenol from electron diffraction

The molecular structure of 4,4′-sulfanidyl-bis-thiophenol (C₁₂H₁₀S₃) has been determined by gas electron diffraction. Assuming identical geometry and D_2h local symmetry for ---SC₆H₄S--- moieties, the following bond lengths (r_g) and bond angles were obtained: C---H = 1.101 ± 0.005, S---H = 1.388 ± 0.019, (C---C)_mean = 1.400 ± 0.003, (S---C)_mean = 1.778 ± 0.004 Å, C_ar---S---C_ar = 103.5 ± 1.3, C---C(S)---C = 120.4 ± 0.3, C(H)---C(H)---H = 119.1 ± 0.9 and C---S---H = 94.6 ± 3.1°. Two ratational forms were found to reproduce the experimental data, characterized by dihedral angles of the benzene rings with respect to the C_arSC_ar plane; ₁ = 67.8 ± 2.0°, ₂ = 4.5 ± 7.2°, and ₁ = 69.4 ± 2.0δ, ₂ = −26.6 ± 7.1°. Identical signs of ₁ and ₂ indicate that the two benzene rings are rotated in the same direction about the respective S_central---C axes.     

Headspace single-drop microextration for the detection of organotin compounds

The performance of single-drop microextraction (SDME), coupled with gas chromatography/mass spectrometry, was assessed for the determination of tributyltin compounds in water and solid samples. Experimental parameters impacting the performance of SDME, such as microextraction solvent and sampling and stirring time, were investigated. Analytical results obtained by SDME were compared with those generated by conventional solid phase microextraction (SPME) and liquid-liquid extraction (LLE) for the determination of TBT in PACS-2 sediment certified reference material (CRM).     

Synthesis of (E)- and (Z)-fluoro-olefin analogues of potent dipeptidyl peptidase IV inhibitors

(E)- and (Z)-fluoro-olefin analogues of potent dipeptidyl peptidase IV inhibitors were synthesized. A Wadsworth-Horner-Emmons reaction, followed by amide formation and reduction of the amide were used for the construction of the α-fluoro-α,β-unsaturated amine functionality.     

The existence of ferrous ferricyanide

Evidence in the literature on the synthesis of ferrous ferricyanide is critically discussed. Pyrolysis and pressure effects on Prussian Blue lead to ferrous ferrocyanide together with decomposition by-products, and not to ferrous ferricyanide. The latter compound could be a precursor in the formation of Turnbull's Blue or an excited state of Prussian Blue, but it is not a stable chemical species.