Wide Variety Of Sample Types Research Articles

Determination of radium-226 in ores, nuclear wastes and environmental samples by high-resolution alpha spectrometry

Management of radioactive wastes requires sensitive, accurate and reliable analytical procedures by which the radionuclides of interest can be determined in a wide variety of sample types. The determination of radium-226 by alpha spectrometry has been investigated critically to determine the exact experimental conditions necessary to achieve these objectives. Refractory solids such as soils, ores, and tailings from uranium mills are dissolved completely by fusion with potassium fluoride in the presence of barium-133 tracer. The fluoride cake is then transposed with sulfuric acid to a pyrosulfate fusion with simultaneous volatilization of all silica and fluoride. Radium is precipitated with barium already present in the sample by addition of lead perchlorate to a dilute hydrochloric acid solution of the pyrosulfate cake. The resulting insoluble sulfates are dissolved in an alkaline solution of diethylenetriaminepentaacetic acid, and the radium and barium sulfates are reprecipitated with acetic acid in the presence of a seeding suspension to produce very small crystals to minimize self-absorption of the alpha particles in getting out of the crystal lattice. The precipitate is mounted on a membrane filter with 0.1-micrometer pores and analyzed by alpha spectrometry. Resolution is about 60 keV full-width-half-maximum which is much better than has been achieved previously from barium sulfate and is as good as is obtained with actinides electrodeposited on polished steel plates. Recovery is over 95% and accuracy is generally as good as the counting statistics obtained will permit. Inaccuracies caused by the differences between radium and the barium tracer and the severe contamination of the detector caused by recoil and volatilization of polonium-210 have been virtually eliminated. Some data on radium-226 in wastes and environmental samples and methods for its removal are presented.

A microanalytical protein assay using laser densitometry

Protein content of a wide variety of sample types may be determined by adsorption of microliter samples onto nitrocellulose, followed by amido black staining and laser densitometry. The method is quite rapid, sensitive, and selective, and dispenses with precipitation and transfer steps.

Volatilization of Sulfur in Fusion Techniques for Preparation of Discs for X-Ray Fluorescence Analysis

The fusion technique for sample preparation for x-ray fluorescence analysis has been proven very successful for a wide variety of sample types. An inherent problem in the fusion technique has been the loss of sulfur during the fusion process. To extend our quantitative major element analysis method for geologic materials we have examined the problem of sulfur volatilization and have tested a variety of fluxes to determine their suitability to quantitatively retain sulfur during fusion, to produce a homogeneous glass disc that is suitable for presentation to an x-ray spectrometer with no additional sample preparation, and to help protect platinumware from attack by sulfide minerals.Highly oxidizing conditions are necessary both to retain sulfur and to protect platinumware from sulfide attack. Previous researchers have shown that sulfur may be lost under reducing conditions. All of the fusions in this study were performed in an oxidizing environment, using a muffle furnace.

Circular differential photoacoustic spectroscopy

A theoretical analysis of left/right circular-polarization modulated photoacoustic spectra is presented. The amplitude of the photoacoustic (PA) signal generated by exciting an absorbing sample alternately with left- and right-circularly polarized light is shown to be proportional to sample circular dichroism, Δα=αL−αR (where αL and αR are sample absorptivities for left and right circularly polarized light, respectively). Expressions appropriate for analyzing photoacoustically detected circular dichroism (referred to as PACD) are developed within the general framework of the Rosencwaig-Gersho model [J. Appl. Phys. 47, 64 (1976)] for the photoacoustic effect in solids and liquids. Extensive calculations based on these expressions are carried out for a number of parameter sets reflecting sample properties, sample cell/detector characteristics, and excitation properties. The results of these calculations indicate that PACD signal strengths for a wide variety of sample types should exceed detectability thresholds, and that PACD should be readily observable for many sample types whose circular dichroism cannot be measured using the conventional transmission techniques. Among this latter class of samples are optically opaque solids and highly scattering suspensions. The expressions for PACD signal strengths are shown to take on particularly simple forms for certain sets of sample properties and excitation modulation frequencies.

Combined headspace and extraction technique for profile analysis by capillary gas chromatography

A method is described whereby a transevaporatoer is used for sampling 60–100 μl of aqueous sample. Volatiles are stripped from the sample either by a stream of helium and collected on a porous polymer, Tenax, or by 0.8 ml of 2-chloropropane and collected on glass beads. The volatiles are thermally desorbed into a precolumn which is connected to a capillary gas chromatographic column for analysis. The technique is shown to be reproducible and suitable for determining chromatographic profiles for a wide variety of sample types.

A Modification to Improve the Performance of Small One Stroke Micropipets

Flameless atomic absorption techniques have greatly extended the capabilities of analytical chemists to determine metallic elements in a wide variety of sample types. However, regardless of the technical excellence of the particular commercially available or homemade atomizer used, the reliability of the analytical work depends upon how well the tiny volumes of sample and standard solutions can be pipetted. Generally the most accepted method of solution handling has been the use of spring-loaded micropipets used with disposable plastic tips. This author has had experience with three examples of these pipets. Two of these utilized two-stage plungers (i.e., the plunger is depressed to the first level for aspiration of a measured amount of solution and pressed to another stop to express and blow out the pipet) and were satisfactory. The third type, a popular, inexpensive, single stroke system was found to be unsatisfactory as received for use in flameless atomic absorption atomizer applications. The reasons for this and a suggested cure for these problems are discussed in this communication.

A Simplified Method for the Determination of Labeled Alkane Hydrocarbons in Mammalian Tissue and Blood After Exposure to Radiolabeled Cigarette Smoke

Abstract A simplified procedure for the determination of 14C- labeled alkanes in mammalian tissue and blood is proposed. A portion of the ethanolic-KOH digest of the sample is counted in a standard toluene scintillator solution; consequently no secondary scintillator solvent or special tissue solubilizer is required. A wide variety of sample types and sizes, including whole organs, can be handled without homogenization or drying. Accuracy and precision are good. Sensitivity is generally inversely related to sample size.

Paper chromatographic separation of multi-component antibiotic mixtures: The acetylated oleandomycins

A paper chromatographic procedure has been described which has proved to be a powerful tool for separating the solvent-soluble antibiotics such as the macrolides and the quinocyclines. The method is rapid, versatile and capable of handling a wide variety of sample types. It has proven extremely valuable in following the synthesis of the several acetylated derivatives of oleandomycin and their appearance and interconversions in biological fluids.