Determination of nanogram levels of silver in suspended materials of streams retained by a membrane filter with the "sampling-boat" technique
No abstract available.
Analytica Chimica Acta↗
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Determination of nanogram amounts of bismuth in rocks by substoichiometric isotope dilution analysis
A rapid procedure suitable for the routine determination of 1–10 ng of bismuth in a silicate rock matrix is described. Results for the U.S. Geological Survey standard rocks are presented. Rocks and minerals are dissolved in hydrofluoric-perchloric acid in the presence of 207 Bi tracer and the silica is removed by evaporation. The perchloric acid residue is taken up in water and bismuth iodide is extracted into methyl isobutyl ketone. After three acid-iodide washes, the bismuth is stripped into water and reacted with a substoichiometric amount of EDTA. Excess of bismuth is extracted as the iodide and the specific activity of the bismuth-EDTA complex is determined.
Analytica Chimica Acta↗
Microcoulometric measurement of water in minerals
A DuPont Moisture Analyzer is used in a microcoulometric method for determining water in minerals. Certain modifications, which include the heating of the sample outside the instrument, protect the system from acid gases and insure the conversion of all hydrogen to water vapor. Moisture analyzer data are compared to concurrent data obtained by a modified Penfield method. In general, there is a positive bias of from 0.1 to 0.2% in the moisture analyzer results and a similarity of bias in minerals of the same kind. Inhomogeneity, sample size, and moisture pick-up are invoked to explain deviations. The method is particularly applicable to small samples.
Analytica Chimica Acta↗
Rapid determination of nanogram amounts of tellurium in silicate rocks
A hydride-generation flameless atomic-absorption technique is used to determine as little as 5 ng g -1 tellurium in 0.25 g of silicate rock. After acid decomposition of the sample, tellurium hydride is generated with sodium borohydride and the vapor passed directly to a resistance-heated quartz cell mounted in an atomic-absorption spectrophotometer. Analyses of 11 U.S. Geological Survey standard rocks are presented.
Analytica Chimica Acta↗
Instrumental activation analysis of coal and fly ash with thermal and epithermal neutrons and short-lived nuclides
Instrumental neutron activation analysis is applied to the determination of about 25 elements in coals and fly ash by means of nuclides with half-lives of less than 48 h ; thermal and epithermal irradiations are used. The results indicate that epithermal activation is preferable for twelve of the elements (Ga, As, Br, Sr, In, Cs, Ba, La, Sm, Ho, W and U). Data for SRM 1632 (coal) and SRM 1633 (fly ash) compare favorably with the results obtained by other investigators.
Analytica Chimica Acta↗
The determination of vanadium in brines by atomic absorption spectroscopy
A standard addition method is described for the determination of vanadium in brines by atomic absorption spectroscopy with a nitrous oxide-acetylene flame. Sample pH is adjusted to 1.0 with concentrated hydrochloric acid and the vanadium is directly extracted with 5% cupferron in methyl isobutyl ketone (MIBK). The ketone layer is then aspirated into the flame and the recorded absorption values are plotted as a function of the concentration of the added metal. As little as 2.5 μg l −1 of vanadium can be detected under the conditions of the procedure. Tungsten and tin interfere when present in excess of 5 and 10 μg ml −1 , respectively. The concentrations of the two interfering ions normally found in brines are well below interference levels.
Analytica Chimica Acta↗
Atomic absorption spectrometric determination of copper, zinc, and lead in geological materials
An atomic absorption spectrometric method is described for the determination of copper, zinc, and lead in geological materials. The sample is digested with HF—HCl—H 2 O 2 ; the final solution for analysis is in 10 % (v/v) HCl. Copper and zinc are determined directly by aspirating the solution into an air—acetylene flame. A separate aliquot of the solution is used for determination of lead; lead is extracted into TOPO-MIBK from the acidic solution in the presence of iodide and ascorbic acid. For a 0.50-g sample, the limits of determination are 10–2000 p.p.m. for Cu and Zn, and 5–5000 p.p.m. for Pb. As much as 40 % Fe or Ca. and 10 % Al, Mg, or Mn in the sample do not interfere. The proposed method can be applied to the determination of copper, zinc, and lead in a wide range of geological materials including iron- and manganese-rich, calcareous and carbonate samples.
Analytica Chimica Acta↗
Determination of dissolved boron in fresh, estuarine, and geothermal waters by d.c. argon-plasma emission spectrometry
A d.c. argon-plasma emission spectrometer is used to determine dissolved boron in natural (fresh and estuarine) water samples. Concentrations ranged from 0.02 to 250 mg l -1 . The emission—concentration function is linear from 0.02 to 1000 mg l -1 . Achievement of a relative standard deviation of ⩽ 3% requires frequent restandardization to offset sensitivity changes. Dilution may be necessary to overcome high and variable electron density caused by differences in alkali-metal content and to avoid quenching of the plasma by high solute concentrations of sodium and other easily ionized elements. The proposed method was tested against a reference method and found to be more sensitive, equally or more precise and accurate, less subject to interferences, with a wider linear analytical range than the carmine method. Analyses of standard reference samples yielded results in all cases within one standard deviation of the means.
Analytica Chimica Acta↗
An automated procedure for the simultaneous determination of specific conductance and pH in natural water samples
An automated, continuous-flow system is utilized to determine specific conductance and pH simultaneously in natural waters. A direct electrometric procedure is used to determine values in the range pH 4–9. The specific conductance measurements are made with an electronically modified, commercially available conductivity meter interfaced to a separate module containing the readout control devices and printer. The system is designed to switch ranges automatically to accommodate optimum analysis of widely varying conductances ranging from a few μmhos cm -1 to 15,000 μmho cm -1 . Thirty samples per hour can be analyzed. Comparison of manual and automated procedures for 40 samples showed that the average differences were 1.3% for specific conductance and 0.07 units for pH. The relative standard deviation for 25 replicate values for each of five samples was significantly less than 1% for the specific conductance determination; the standard deviation for the pH determination was ⩽ 0.06 pH units.
Analytica Chimica Acta↗
Flame and flameless atomic-absorption determination of tellurium in geological materials
The sample is digested with a solution of hydrobromic acid and bromine and the excess of bromine is expelled. After dilution of the solution to approximately 3 M in hydrobromic acid, ascorbic acid is added to reduce iron(III) before extraction of tellurium into methyl isobutyl ketone (MIBK). An oxidizing air-acetylene flame is used to determine tellurium in the 0.1–20 ppm range. For samples containing 4–200 ppb of tellurium, a carbon-rod atomizer is used after the MIBK extract has been washed with 0.5 M hydrobromic acid to remove the residual iron. The flame procedure is useful for rapid preliminary monitoring, and the flameless procedure can determine tellurium at very low concentrations.
Analytica Chimica Acta↗
Atomic-absorption spectrometric determination of cobalt, nickel, and copper in geological materials with matrix masking and chelation-extraction
An atomic-absorption spectrometric method is reported for the determination of cobalt, nickel, and copper in a variety of geological materials including iron- and manganese-rich, and calcareous samples. The sample is decomposed with HP-HNO 3 and the residue is dissolved in hydrochloric acid. Ammonium fluoride is added to mask iron and 'aluminum. After adjustment to pH 6, cobalt, nickel, and copper are chelated with sodium diethyl-dithiocarbamate and extracted into methyl isobutyl ketone. The sample is set aside for 24 h before analysis to remove interferences from manganese. For a 0.200-g sample, the limits of determination are 5–1000 ppm for Co, Ni, and Cu. As much as 50% Fe, 25% Mn or Ca, 20% Al and 10% Na, K, or Mg in the sample either individually or in various combinations do not interfere. Results obtained on five U.S. Geological Survey rock standards are in general agreement with values reported in the literature.
Analytica Chimica Acta↗
Matrix modification with silver for the electrothermal atomization of arsenic and selenium
Silver as a matrix modifier is shown to improve the carbon-rod atomization of both arsenic and selenium for atomic absorption spectrometry. Compared to nickel, the efficiency of silver is greater for arsenic and about the same for selenium. Silver fulfils two functions in its reaction, namely stabilization during the ashing stage and enhancement of absorbance in the final atomization.
Analytica Chimica Acta↗
Application of capillary gas chromatography mass spectrometry/computer techniques to synoptic survey of organic material in bed sediment
A bed sediment sample taken from an area impacted by heavy industrial activity was analyzed for organic compounds of environmental significance. Extraction was effected on a Soxhlet apparatus using a freeze-dried sample. The Soxhlet extract was fractionated by silica gel micro-column adsorption chromatography. Separation and identification of the organic compounds was accomplished by capillary gas chromatography/mass spectrometry techniques. More than 50 compounds were identified; these include saturated hydrocarbons, olefins, aromatic hydrocarbons, alkylated polycyclic aromatic hydrocarbons, and oxygenated compounds such as aldehydes and ketones. The role of bed sediments as a source or sink for organic pollutants is discussed.
Analytica Chimica Acta↗
Automated standardization technique for an inductively-coupled plasma emission spectrometer
The manifold assembly subsystem described permits real-time computer-controlled standardization and quality control of a commercial inductively-coupled plasma atomic emission spectrometer. The manifold assembly consists of a branch-structured glass manifold, a series of microcomputer-controlled solenoid valves, and a reservoir for each standard. Automated standardization involves selective actuation of each solenoid valve that permits a specific mixed standard solution to be pumped to the nebulizer of the spectrometer. Quality control is based on the evaluation of results obtained for a mixed standard containing 17 analytes, that is measured periodically with unknown samples. An inaccurate standard evaluation triggers restandardization of the instrument according to a predetermined protocol. Interaction of the computer-controlled manifold assembly hardware with the spectrometer system is outlined. Evaluation of the automated standardization system with respect to reliability, simplicity, flexibility, and efficiency is compared to the manual procedure.
Analytica Chimica Acta↗
The determination of silver in silicate rocks by electrothermal atomic absorption spectrometry
Silver is extracted from a 20% tartaric acid solution by using butyl acetate and diphenylthiourea, and the organic layer is analyzed directly by the graphite-furnace technique. The precisions is ca. 8% as estimated from multiple analysis of 13 standard rocks; there are no systematic errors. The detection limit is 2.4 ppb for 250-mg samples.
Analytica Chimica Acta↗
Extraction spectrophotometric determination of niobium in rocks with sulfochlorophenol S
After acid decomposition and potassium pyrosulfate fusion, niobium (1—26 ppm) is separated from interfering elements by extraction into methyl isobutyl ketone from 6 M H 2 SO 4 —2 M HF and back-extracted into water. The niobium—sulfochloro-phenol S complex is extracted into amyl alcohol.
Analytica Chimica Acta↗
X-ray fluorescence determination of titanium in geological materials
No abstract available.
Analytica Chimica Acta↗
Determination of trace amounts of tin in geological materials by atomic absorption spectrometry
An atomic absorption method is described for the determination of traces of tin in rocks, soils, and stream sediments. A dried mixture of the sample and ammonium iodide is heated to volatilize tin tetraiodide -which is then dissolved in 5 % hydrochloric acid, extracted into TOPO-MIBK, and aspirated into a nitrous oxide-acetylene flame. The limit of determination is 2 p.p.m. tin and the relative standard deviation ranges from 2 to 14 %. Up to 20 % iron and 1000 p.p.m. Cu, Pb, Zn, Mn, Hg, Mo, V, or W in the sample do not interfere. As many as 50 samples can be easily analyzed per man-day.
Analytica Chimica Acta↗