Showing papers in "Analytical Chemistry in 1979"

Sequential extraction procedure for the speciation of particulate trace metals

Abstract: An analytical procedure involving sequential chemicai extractions has been developed for the partitioning of particulate trace metals (Cd, Co, Cu, Ni, Pb, Zn, Fe, and Mn) into five fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter, and residual. Experimental results obtained on replicate samples of fluvial bottom sediments demonstrate that the relative standard deviation of the sequential extraction procedure Is generally better than =10%. The accuracy, evaluated by comparing total trace metal concentrations with the sum of the five Individual fractions, proved to be satisfactory. Complementary measurements were performed on the Individual leachates, and on the residual sediments following each extraction, to evaluate the selectivity of the various reagents toward specific geochemical phases. An application of the proposed method to river sediments is described, and the resulting trace metal speciation is discussed.

Calibration of methanol and ethylene glycol nuclear magnetic resonance thermometers

Abstract: A guadratic equation describing the difference in temperature of a methanol sample as a function of the separation (in H/sub 2/) between the OH proton and the CH/sub 3/ protons, and a linear relationship between temperature and separation of the OH protons and CH/sub 2/ protons of ethylene glycol performed at 220 MHz were reported. This data demonstrated that Van Geet's 60-MHz calibration equations may be confidently scaled up to 220 MHz, and the agreement suggests that scaling to even higher frequencies should not introduce appreciably larger errors. A Varion HR-220 spectrometer with pulse Fourier transform capability was used. Methanol or glycol was used in an open sample tube for thermocycle measurements. Experimental data was included. The relationship between chemical shift and temperature was reported in calibiaton curve of methanol and glycol at 220 MHz as a function of temperature. 1 table, 1 figure, (DR)

The Generalized Standard Addition Method.

Abstract: : The normal standard addition methods assumes that, for any one analyte in a sample there is an analytical sensor which responds to that analyte and no other unknown in the sample. When the analytical sensor is not completely selective, so-called interference effects results which can be a major source of error. The generalized standard addition method provides a means of accounting for the interference effects, to actually quantify the magnitude of the interferences, and simultaneously to determine the analyte concentrations. (Author)

Triple quadrupole mass spectrometry for direct mixture analysis and structure elucidation.

Abstract: : The triple quadrupole mass spectrometer is shown to be a simple and highly efficient system for the observation of the fragmentation pattern of selected ions. The instrument consists of, in series, a CI/EI ion source, a quadrupole mass filter, an RF-only quadrupole collision chamber, a second mass filter, and an electron multiplier. The high sensitivity of the MS/MS technique with quadrupoles depends particularly on the highly efficient low energy collision-induced dissociation process in the strong focusing RF quadrupole field. Detection limits for methane and nitrobenzene of 10 to the minus 15 mole are shown. Analysis of a mixture of six components, including two isomers and an isobaric compound is presented. Chemical noise is virtually eliminated by the selection of both parent and fragment ion. An application of the system for structure elucidation is also described. (Author)

Thin film deposition by the electrospray method for californium-252 plasma desorption studies of involatile molecules

Abstract: An electrospray system and procedure has been developed for the routine preparation of thin films of involatile molecules for analytical measurements. An anode-cathode design has been developed and conditions for reproducible performance have been established. Solvent systems for polar and nonpolar molecules have been investigated and electron microscopy measurements have been made on the microstructure of the deposits and fraction of surface coverage. The method does not appear to degrade thermally-labile molecules. 4 figures.

Neutron-capture prompt .gamma.-ray activation analysis for multielement determination in complex samples

Abstract: Gamma-ray spectra were taken up to 11 MeV from a wide range of samples and elemental standards while under neutron irradiation to determine the elements whose prompt ..gamma.. rays are observable and can be used for analytical measurement. Up to 17 elements from among the set H, B, C, N, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Mn, Fe, Cd, Nd, Sm, and Gd are measurable in samples of coal, fly ash, orchard leaves, and bovine liver by neutron-capture prompt ..gamma..-ray activation analysis (PGAA). The combination of PGAA and instrumental neutron activation analysis (which uses the same equipment) can be used to measure concentrations of 40 to 50 elements in individual samples of many types of material. Concentrations are reported for the elements measurable by PGAA in National Bureau of Standards Standard Reference Materials: coals (SRMs 1632, 1632a, 1635), fly ashes (1633, 1633a), orchard leaves (1571), and bovine liver (1577). 9 figures, 6 tables.

Determination of part-per-trillion concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin in fish.

Abstract: Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Determination of part-per-trillion concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin in fish L. L. Lamparski, T. J. Nestrick, and R. H. Stehl Anal. Chem., 1979, 51 (9), 1453-1458• DOI: 10.1021/ac50045a023 • Publication Date (Web): 01 May 2002 Downloaded from http://pubs.acs.org on February 16, 2009