Spherical Particles of Zirconia-Titania of Hexagonal Structure from a Neutral Amine Route

Through the sol–gel process, using the so-called neutral amine route, spherical particles of 1:1 zirconia–titania were synthesized from zirconium(IV) and titanium(IV) butoxides as well as 1,12-diaminododecane as precursor species. The obtained product exhibited a hexagonal structure, as determinated by X-ray diffraction data. The obtained material was also characterized by thermogravimetry, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, and surface area measurements. Despite the release of template molecules on heating, the spherical morphology was retained up to about 1200°C, at which the disruption of the spheres took place.     

Effects of Adsorbed Polyaniline on Redox Process on MoO3 Surface

The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press.     

Some optical studies with the air-acetylene flame

The application of Schlieren and shadow techniques for the study of flame processes is discussed in relation to analytically useful premixed flames. The information obtained, particularly with shadowgraphs, may be correlated with the measured signals and signal noise in atomic-absorption and flame-emission spectrometry.     

Purification of glycogen phosphorylase isozymes by metal-affinity chromatography.

Mammalian phosphorylase isozymes from muscle, brain and liver were expressed in Escherichia coli and purified from the crude bacterial cell extracts in one step using a copper-loaded, metal-affinity matrix. Good chromatographic behavior, enzyme activity and protein stability were maintained by judicious choice of pH and buffer which contained 250 mM sodium chloride and 25 mM beta-glycerophosphate at pH 7.0. Small amounts of beta-mercaptoethanol and EDTA in the buffers further stabilized the enzymes, but stripped some of the metal from the column which, nonetheless, retained good chromatographic characteristics. Owing to the presence of multiple surface histidine residues in the phosphorylase dimers, good enzyme purities (90-98%) and recoveries (>90%) were routinely obtained from crude bacterial lysates after two passes through the copper column. Of the various metal ions which were investigated, Cu2+ gave the best chromatographic results. Imidazole gradients at constant pH were used to selectively desorb the phosphorylase from the metal column whose capacity for phosphorylase binding in the presence of bacterial proteins exceeded 30 mg enzyme per milliliter of matrix.     

Influence of water on conditions in the inductively coupled argon plasma

Aqueous media are used almost universally for sample introduction in both inductively coupled plasma atomic emission spectrometry (ICPAES) and in inductively coupled plasma/mass spectrometry (ICP/MS). In the process of aqueous sample introduction a substantial mass of water is introduced into the plasma as a combined aerosol/vapor mixture. In the present studies, the masses of water present as aerosol and vapor were controlled, in order to examine their separate influence on the key plasma properties of electron density n_e and ionization temperature T_ion. Water loading in the plasma was indeed found to have a major influence on n_e and T_ion, and plots of these parameters as a function of water loading are presented. Plasma viewing height and operating power were also found to be important variables in influencing the way in which water interacts with the plasma. The implications of water loading on background emission and noise level are also considered.     

Evaporation characteristics of organic solvent aerosols used in analytical atomic spectrometry

A simple theoretical approach has been used to calculate changes in aerosol droplet diameters caused by evaporation in a solvent-vapor saturated atmosphere. The results for a range of solvents likely to be encountered in analytical atomic spectrometry are discussed, with particular reference to their possible effects on nebulization and atomization efficiencies, and hence on sensitivities attainable in nebulizer-based atomic spectrometry. The importance of droplet solvent evaporation is also discussed with respect to the aspiration rates which may be usefully employed when organic solvents are aspirated into an inductively coupled plasma.     

Studies in atomic-fluorescence spectroscopy--VIII. Atomic fluorescence and atomic absorption of thallium and mercury with electrodeless discharge tubes as sources

Atomic-fluorescence measurements, with microwave-excited electrodeless discharge tubes as sources of excitation, are described for thallium and mercury. The limits of detection by atomic fluorescence are 0.12 ppm for thallium and 0.08 ppm for mercury; the corresponding limits by atomic absorption (using the same instrument and source) are 6 and 10 times as great. The preparation, operation and spectral characteristics of thallium and mercury discharge tubes are described and comparisons are made with a thallium hollow cathode lamp and thallium and mercury spectral discharge lamps.     

MAGIC-LC/FT-IR spectrometry

The FTIR spectra of uracil and thymine were studied at different concentrations in pure Ar matrices as well as in H₂O or HCl doped Ar matrices. The spectral results suggest the presence of open dimers in associated uracil and thymine. The structure of heterodimers of uracils with H₂O and HCl is discussed.     

Optimization of thermostated electrodeless discharge lamps for analytical atomic spectrometry

Thermostated and unthermostated electrodeless discharge lamps (EDL's) operated at 2450 MHz with either an A-antenna or a $\text{3}\text{4}$-wavelength Broida cavity have been critically studied with respect to the effect of type and pressure of fill gas, lamp temperature, microwave power and the form of element and/or compound within the lamp, upon the source radiant output, atomic absorption and atomic fluorescence signals of Zn-213·8 nm, Pb-283·3 nm, Mn-279·5 nm, Hg-253·7 nm and Tl-377·6 nm. Temperature control of electrodeless discharge lamps eliminates most of the problems which have previously plagued their operation. Also as a result of these studies, certain misconcepts in the operation and characteristics of electrodeless discharge lamps have been clarified; e.g., the ‘skin effect’ is present in many electrodeless discharge lamps, but all lamps also exhibit a homogeneous glow discharge; at high microwave powers and/or at high lamp temperatures, spectral lines apparently exhibit little self-absorption and self-reversal; and most important, control of lamp temperature is the most critical parameter controlling spectral output because atomization within the lamps is predominantly thermal in origin. Also, contrary to the conclusions reached by some workers evaluating the analytical usefulness of atomic fluorescence flame spectrometry, it is shown that detection limits one-to-three orders of magnitude lower result when thermostated EDL's are used in atomic fluorescence spectrometry with C₂H₂-air flames.