Synthesis of 3-Aminopyrocatechol via Lithiated Intermediates

We report the synthesis of 3-aminopyrocatechol (7) through electrophilic amination of lithiated pyrocatechol, protected in the form of a ketal. For this purpose the lithiation reaction of protected pyrocatechol (1) was studied. The synthesis of compounds (3) was achieved by the reaction of organolithium derivative (2) and a series of electrophilic reagents. Lithium-t-butyl-N-tosyloxycarbamate (5) was used as the electrophilic aminating reagent. With the cupro derivative (4) the protecting groups in compound (6) are removed in an acid medium by heating in ethanol-HCl solution (4:1).     

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.     

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     

Fragmentation and erosion of two-dimensional aggregates in shear flow

We consider single two-dimensional aggregates containing glass particles trapped at a water/oil or water/air interface. Two modes for aggregate break-up are observed: break-up by fragmentation into a few parts and break-up by erosion of single particles. We have studied the critical shear rate for these modes as a function of the aggregate size. Two different particle sizes were used. The smaller particles, with a radius of 65 microm, form aggregates that break up predominantly by erosion at a shear rate between 0.5 and 0.7 s(-1). This value hardly depends on the size of the aggregates. The larger particles, with a radius of 115 microm, form aggregates that break by erosion or by fragmentation. In both modes, the critical shear rate again depends only weakly on the size of the aggregates and ranges between 1.6 and 2.2 s(-1). Also the structural changes inside the aggregate before break-up were studied. The aggregate behavior at the water/air and water/oil interfaces is quite similar. The critical shear rate for break up was also modeled. The model shows in both modes a weak dependence of the critical shear rate on the aggregate size, which is consistent with the experimental observations. The kinetics of the erosion process was also modeled and compared with the experimentally obtained time dependence of the aggregate size. The differences in the large and small particle systems can be attributed to the occurrence of friction forces between the particles, which one expects to be much larger for the large particle system, due to the stronger two-particle interaction.     

Cadmium determination in natural waters at the limit imposed by European legislation by isotope dilution and TiO<Subscript>2</Subscript> solid-phase extraction

The cadmium content in surface water is regulated by the last European Water Framework Directive to a maximum between 0.08 and 0.25 μg L⁻¹ depending on the water type and hardness. Direct measurement of cadmium at this low level is not straightforward in real samples, and we hereby propose a validated method capable of addressing cadmium content below μg L⁻¹ level in natural water. It is based on solid-phase extraction using TiO₂ nanoparticles as solid sorbent (0.05 g packed in mini-columns) to allow the separation and preconcentration of cadmium from the sample, combined to direct isotope dilution and detection by inductively coupled plasma mass spectrometry (ID-ICP-MS). The extraction setup is miniaturised and semi-automated to reduce risks of sample contamination and improve reproducibility. Procedural blanks for the whole measurement process were 5.3 ± 2.8 ng kg⁻¹ (1 s) for 50 g of ultrapure water preconcentrated ten times. Experimental conditions influencing the separation (including loading pH, sample flow rates, and acid concentration in the eluent) were evaluated. With isotope dilution the Cd recovery rate does not have to be evaluated carefully. Moreover, the mathematical model associated to IDMS is known, and provides transparency for the uncertainty propagation. Our validation protocol was in agreement with guidelines of the ISO/IEC 17025 standard (chapter 5.4.5). Firstly, we assessed the experimental factors influencing the final result. Secondly, we compared the isotope ratios measured after our separation procedure to the reference values obtained with a different protocol for the digested test material IMEP-111 (mineral feed). Thirdly, we analysed the certified reference material BCR-609 (groundwater). Finally, combined uncertainties associated to our results were estimated according to ISO-GUM guidelines (typically, 3–4% k = 2 for a cadmium content of around 100 ng kg⁻¹). We applied the developed method to the groundwater and wastewater samples ERM-CA615 and BCR-713, respectively, and results agreed with certificate values within uncertainty statements.