Forced Hydrolysis of Fe3+ Ions in NH4Fe(SO4)2 Solutions Containing Urotropin

The effects of urotropin on the hydrolysis of Fe3+ ions in NH4Fe(SO4)2 Solutions at 90 °C were investigated using X-ray powder diffraction, 57Fe Mössbauer spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Three concentrations of NH4Fe(SO4)2 Solutions, 0.03, 0.1 and 0.5 M, with varying initial amounts of urotropin were used in the experiments. Chemical and structural properties of the precipitates strongly depended on the concentrations of the reactants and the time of hydrolysis. In the early stages of Fe3+ hydrolysis, samples were dominantly amorphous. α-FeOOH, α-Fe2O3 and NH4Fe3(OH)6(SO4)2 were crystalline phases detected in the precipitates; however, the specific phase composition of each precipitate depended on the experimental conditions. The possible formation of schwertmannite was not proven in the precipitates. It was suggested that the particles of amorphous fraction, as well as α-FeOOH particles, contained significant amounts of sulphates on external and internal surfaces due to the specific adsorption. Regularity in the phase composition of the precipitates, as a function of the experimental conditions, was found. Crystallite sizes of oxides were estimated on the basis of the broadening of diffraction lines. Mossbauer spectroscopy indicated super-paramagnetic behavior of a-FeOOH particles. Formation of α-FeOOH particles of colloidal dimensions was proven by transmission electron microscopy

Molecular Transport between Two Phases in a Microchannel.

Today, microfabricated devices (microchips) have attracted considerable attention because of their vast applicability and versatility. Most published reports utilizing microchips to separate and detect analysis of interest have concentrated on using electrokinetically driven separation schemes. Investigations from a different standpoint have been few in number. However, microchips offer advantages concerning the scale merits of microspace, such as a short diffusion distance and the high interface-to-volume ratio, the specific interface area; we thus considered that they are an ideal tool to study molecular transport between two different phases, i.e., solvent extraction. In the present paper, we report on the first demonstration using a microchip to study molecular between two phases

Integration of Flow Injection Analysis and Zeptomole-Level Detection of the Fe(II)-<i>o</i>-Phenanthroline Complex

Microchannels having a 150×100 µm cross section were fabricated in a quartz glass chip as a component in an integrated flow injection analysis (FIA) system. They were put to use for flow, mixing, reaction, and detection. The reaction system was a chelating reaction of divalent iron ion with o-phenanthroline (o-phen), and a photothermal microscope was applied for the ultra-sensitive detection of the non-fluorescent reaction product. Nano liter levels of solutions were introduced and transported by capillary action and mixed by molecular diffusion. Zeptomole levels of the reaction product were detected quantitatively. This was the first demonstration of an on-chip chemical determination device which integrates the primitive FIA system without using electroosmotic liquid control or fluorometric determination

Sub-Zeptomole Detection in a Microfabricated Glass Channel by Thermal-Lens Microscopy.

A thermal-lens microscope which we developed was applied to an ultramicro quantity determination of a dye in an aque-ous solution filling a microchannel (150 µm wide and 100 µm deep) fabricated in a quartz glass substrate. The detection volume, which corresponded to the confocal volume, was estimated to be 1.3 fl. The detection limit of the dye molecules was 160 ymol, and the calibration line showed good linearity in the sub-zmol-to-zmol region. This detection sensitivity is equivalent to that of laser-induced fluorometry. The thermal-lens signal measured in the microchannel was more stable than that measured in a liquid micro space between a slide glass and a cover glass, which was much wider than the microchannel. This may have been due to a suppression of convection in the microchannel. The thermal lens method can be applied to non-fluorescent chemical species, and is thus very suitable detection method for integrated chemistry sys-tems