Liquid-phase microextraction in a microfluidic-chip – High enrichment and sample clean-up from small sample volumes based on three-phase extraction

In this work, a microfluidic-chip based system for liquid-phase microextraction (LPME-chip) was developed. Sample solutions were pumped into the LPME-chip with a micro-syringe pump at a flow rate of 3–4 μL min⁻¹. Inside the LPME chip, the sample was in direct contact with a supported liquid membrane (SLM) composed of 0.2 μL dodecyl acetate immobilized in the pores of a flat membrane of polypropylene (25 μm thickness). On the other side of the SLM, the acceptor phase was present. The acceptor phase was either pumped at 1 μL min⁻¹ during extraction or kept stagnant (stop-flow). Amitriptyline, methadone, haloperidol, loperamide, and pethidine were selected as model analytes, and they were extracted from alkaline sample solution, through the SLM, and into 10 mM HCl or 100 mM HCOOH functioning as acceptor phase. Subsequently, the acceptor phase was either analyzed off-line by capillary electrophoresis for exact quantification, or on-line by UV detection or electrospray ionization mass spectrometry for time profiling of concentrations. The LPME-chip was found to be highly effective, and extraction efficiencies were in the range of 52–91%. When the flow of acceptor phase was turned off during extraction (stop-flow), analyte enrichment increased linearly with the extraction time. After 10 min as an example, amitriptyline was enriched by a factor of 42 from only 30 μL sample solution, and after 120 min amitriptyline was enriched by a factor of 500 from 320 μL sample solution. This suggested that the LPME-chip has great potentials for very efficient analyte enrichments from limited sample volumes in the future.     

A Mössbauer spectroscopy study of chemically prepared ultrafine particles of amorphous (Fe1-xCox)60B40

Ultrafine amorphous alloy particles of (Fe_1-x Co_x)₆₀B₄₀ with x=0.1, 0.3, 0.5, 0.7, and 0.9 have been prepared by reduction of the metal ions using KBH₄ in aqueous solution. electron microscopy shows that the particle size is of the order of 20 nm. Mössbauer spectroscopy has been used to elucidate the magnetic properties of the particles.     

The ferric/ferrous ratio in basalt melts at different oxygen pressures

Samples of two types of natural basalt were equilibrated over a range of oxygen pressures at four different temperatures, and then quenched to room temperature. Except at the lowest temperature, where magnetic crystals formed under the most oxidizing conditions, totally amorphous samples were obtained. The Mössbauer spectra of 45 samples of the quenched basaltic melts were measured at room temperature. The relationship obtained between the oxidation state and oxygen fugacity differs to some extent from those relations previously described in the literature, in not yielding a linear relationship between log(farric/ferrous) and log(fo₂). This might indicate a more involved redox process than that described by a simple reaction between oxides and/or the influence of the cation composition in the process of glass formation. An investigation was made of the kinetics of the redox process. For the experimental setup used, redox equilibrium would be reached within three hours. Finally, three naturally quenched basalt glasses were analyzed for comparison; two showed lower oxidation states than previously found in Icelandic rocks.     

Degradation of blood in the human digestive tract

Samples of human faeces from patients suffering from intestinal bleeding have been studied by use of Mössbauer spectroscopy. It is shown that it is possible to follow the degradation of blood in the digestive tract.     

A study of the sump beaver's dental enamel

The nature of the iron-containing phase in the dental enamel of sump beaver incisors has been studied by use of Mössbauer spectroscopy. All iron atoms are found to be trivalent and to be present in particles exhibiting superparamagnetic relaxation. The iron-containing phase has Mössbauer parameters similar to those of ferritin.     

Immobilization of aryl and alkynyl groups onto glassy carbon surfaces by electrochemical reduction of iodonium salts

A new versatile method has been developed for the electrochemically assisted grafting of carbon materials. The approach is based on the reduction of iodonium salts and allows the immobilization not only of aryl groups, such as phenyl or nitrophenyl, but also of alkynyl groups under mild conditions. In particular, the immobilization of alkynyl groups is important because such grafting cannot be accomplished using any other known reductive procedure. The electrochemical properties of the grafted surfaces with estimated coverages of (4-6) x 10(-)(10) mol cm(-)(2) are investigated against the ferrocene and Fe(CN)(6)(3)(-) solution probes. The analysis of the surfaces is carried out by means of cyclic voltammetry and X-ray photoelectron spectroscopy.     

Site of gas-phase methylation of l-phenyl-2-aminopropane

The regioselectivity of methyl cation transfer from (CH₃)₂F⁺, (CH₃)₂Cl⁺ and (CH₃)₃O⁺ to 1-phenyl-2-aminopropane was studied by Fourier transform ion cyclotron resonance in combination with collision-induced dissociation and neutralization-reionization mass spectrometry of the stable [M + CH₃]⁺ ions formed in a chemical ionization source. The (CH₃)₂F⁺ ion transfers a methyl cation to the NH₂ group and the phenyl ring with almost equal probability. Predominant CH₃⁺ transfer to the NH₂ group is observed for the (CH₃)₂Cl⁺ ion whereas the (CH₃)₃O⁺ ion reacts almost exclusively at the amino group. The preference for methylation at NH₂ is discussed in terms of a lower methyl cation affinity of the phenyl ring than of the amino group and the existence of an energy barrier for methylation of the phenyl moiety.