Gelatin films with very high surface hardness

Microhardness (H) of gelatin dry cast films was measured in the 100–250°C range. A strong H increase with temperature from 330 MPa up to 450 MPa was observed in the first cycle. The H values reached in the subsequent cycles are higher than those obtained in the preceding ones, surpassing the hardness of all commercial synthetic polymers and soft metals. Results are discussed in terms of crosslinking between side-chain reactive groups.     

Application of high-surface-area ZrO2 in preconcentration and determination of 18 elements by on-line flow injection with inductively coupled plasma atomic emission spectrometry

A flow-injection analysis (FIA) system incorporating a micro-column of ZrO₂ has been used for the development of an on-line multi-element method for the simultaneous preconcentration and determination of Al, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Mo, Ni, Pb, Tl, V, Sb, Sn, and Zn by inductively coupled plasma atomic emission spectrometry (ICP–AES). The conditions for quantitative and reproducible preconcentration, elution, and subsequent on-line ICP–AES determination were established. A sample (pH 8) is pumped through the column at 3 mL min^–1 and sequentially eluted directly into the ICP–AES with 3 mol L^–1 HNO₃. With a sample volume of 100 mL and an elution volume of 1 mL signal enhancement 100 times better than for conventional continuous aspirating systems was obtained for the elements studied. The reproducibility (RSD %) of the method at the 10 ng mL^–1 level in the eluate is acceptable – less than 8% for five replicates. Recoveries between 95.4% and 99.9% were obtained for the elements analysed. ZrO₂, with a specific surface area of 57 m² g^–1 and a capacity of approximately 5 mg g^–1 for the elements studied, was synthesized by hydrolysis of ZrCl₄. The preconcentration system was evaluated for several simple synthetic matrices, standard water samples and synthetic seawater. The effect of foreign ions on the efficiency of preconcentration of the elements studied was investigated. The application of a micro-column filled with high-surface-area ZrO₂ and flow injection inductively coupled plasma atomic emission spectrometry enables preconcentration and simultaneous determination of 18 elements at low concentrations (ng L^–1) in different water samples.     

Sorption of Co(II), Ni(II), Ag(I) and Au(III) on pyrazolone-containing inorganic sorbents

The sorption capacity of 3-methyl-1-phenyl-pyrazolone-5 (HMPP)- modified inorganic sorbents has been investigated. The new sorbents are suitable for simultaneous concentration of the 3d elements being investigated over a wide pH range. Choosing appropriate pH values for the corresponding elements, it is possible to achieve their separate extraction.     

Discussion of parameters associated with the determination of arsenic by electrothermal atomic absorption spectrometry in slurried environmental samples

A slurry sampling-fast program procedure has been developed for the determination of arsenic in plants, soils and sediments by electrothermal atomic absorption spectrometry. Efficiencies of various single and mixed modifiers for thermal stabilization of arsenic and for a better removal of the matrix during pyrolysis step were compared. The influence of the slurry concentration, amounts of modifier and parameters of the pyrolysis step on the As integrated absorbance signals have been studied and a comparison between fast and conventional furnace programs was also made. The ultrasonic agitation of the slurry followed by a fast electrothermal program using an Ir/Mg modifier provides the most consistent performance in terms of precision and accuracy. The reliability of the whole procedure has been compared with results obtained after application of a wet digestion method with an HF step and validated by analyzing eleven certified reference materials. Arsenic detection and quantitation limits expressed on dry sample matter were about 30 and 100 micrograms kg-1, respectively.     

Synthesis and structural characterization of neutral higher-coordinate silicon(IV) complexes with tridentate dianionic chelate ligands

The neutral pentacoordinate silicon(IV) complexes 8 and 9 with an SiO2N3 skeleton and the neutral hexacoordinate silicon(IV) complex 10.1/2 CH3CN with an SiO4N2 skeleton were synthesized, starting from tetra(cyanato-N)silane or tetra(thiocyanato-N)silane. Compounds 8 and 9 contain one tridentate dianionic ligand derived from 4-[(2-hydroxyphenyl)amino]pent-3-en-2-one and two monodentate singly charged cyanato-N or thiocyanato-N ligands bound to the silicon(IV) coordination center, whereas the silicon(IV) center of 10 is coordinated by two of these tridentate dianionic ligands. All compounds were characterized by single-crystal X-ray diffraction and solid-state and solution NMR spectroscopy. To get more information about the stereochemistry of the compounds studied, the experimental investigations were complemented by computational studies.     

Spirocyclic zwitterionic lambda5Si-silicates with two bidentate ligands derived from alpha-amino acids or alpha-hydroxycarboxylic acids: synthesis, structure, and stereodynamics

A series of zwitterionic lambda(5)Si-silicates with a (2,2,6,6-tetramethylpiperidinio)methyl group and two identical bidentate ligands derived from glycine, (S)-alanine, (S)-phenylalanine, glycolic acid, (S)-lactic acid, (S)-3-phenyllactic acid, or (S)-mandelic acid were synthesized and structurally characterized (solution and solid-state NMR spectroscopy; single-crystal X-ray diffraction). The chiral lambda(5)Si-silicates with ligands derived from optically active alpha-amino acids or alpha-hydroxycarboxylic acids were isolated as enantiomerically and diastereomerically pure compounds that undergo a (Lambda)/(Delta)-epimerization in solution.     

Spektrophotometrische Untersuchung der Eisen(III)-Komplexe mit o-Methylbenzamidoxim

The complex formation of Fe³⁺ with o-methyl benzamide oxime was studied spectrophotometrically in methanol solution. The stepwise process gives complexes 1∶1, 1∶2 and 1∶3. The formation constants are lgK ₁ = lg β₁ = 1,88 ± 0,12, lgK ₂ = 3,53 ± 0,2, lgK ₃ = 4,96 ± 0,2, lg β₂ = 1,65 ± 0,32 and lg β₃ = 1,43 ± 0,4, whereK ₃ = β₁ · β₂ · β₃. All measurements were carried out at 25°C and an ionic strength μ=1.     

A participatory improvement activity of the EC-JRC to improve metrology in chemistry in EU candidate countries

In 2000, the European Commission-Joint Research Centre, Institute for Reference Materials and Measurements (EC-JRC-IRMM) set up a project to improve the scientific basis for metrology in chemistry (MiC) in EU candidate countries. Several activities were initiated (training, fellowships, sponsoring seminars, conferences and participation in the International Measurement Evaluation Programme – IMEP). A particular initiative, discussed here, was to assist each of the national measurement institutes of these countries to write a status report on MiC. Most importantly, the report was intended to be the end-product of a process to document the current status of MiC. Intentionally, this process involved not only the providers of services in MiC but all the major stakeholders in this activity (e.g. major field laboratories, accreditation bodies, regulatory bodies, educators, professional bodies). The status reports are intended to be the first step of the future improvement process. In those countries where writing of the status reports has been started (Slovenia, Poland, Bulgaria and Estonia) the first signs are that this process leads to better co-operation and particularly a better understanding of what the future role and activities of each of these stakeholders should be. Correspondence to N. Majcen