Applied Spectroscopy

Omenetto, N.; Hart, L. P.; Winefordner, J. D.

doi: 10.1366/0003702844554945pmid: N/A

It is shown that the technique of intermodulated fluorescence can effectively correct for scattering problems in analytical flame fluorescence spectroscopy. When two laser beams, amplitude-modulated at different frequencies f1 and f2 and counterpropagated colinearly throughout an atomizer, are tuned to the absorption transition of the element of interest, non-linear mixing of the fluorescence signal results, due to saturation effects. By extraction of the signal at the sum or difference frequency, f2 ± f2, the linear scattering component of the spectrum can be essentially eliminated. This has been demonstrated for a sodium solution nebulized in a premixed, laminar, argon-oxygen-hydrogen flame. Because the modulation signal can be observed only at the intersection volume between the two beams, this technique constitutes a powerful tool for spatially resolved combustion diagnostics.

Anderson, T. A.; Parsons, M. L.

doi: 10.1366/0003702844554846pmid: N/A

The spectra of the group IIIA elements observed in an ICP have been tabulated in the wavelength range from 1995 to 6005 Å These spectra have been compared to a list of those analytical lines most commonly used for the 71 elements analyzed for by an ICP The results of these comparisons have been used to develop spectral interference tables which predict those spectral interferences due to the group IIIA elements in ICP spectroscopy In addition, the spectral interferences due to the alkaline earth elements have been included

Mianzhi, Zhuang; Barnes, Ramon M.

doi: 10.1366/0003702844554855pmid: N/A

A procedure is described for the inductively coupled plasma emission spectroscopic determination of Cd, Co, Cu, Fe, Mo, V, and Zn in < 1 mL of serum after digestion in nitric and perchloric acids and preconcentration with a poly(dithiocarbamate) resin Recoveries are 91 to 106% The determination of As and Se in serum by hydride generation and ICP-AES is performed after the interference of Cu on Se hydride generation was reduced by complexation of the Cu with poly(acrylamidoxime) resin Verification with NBS-SRMs as well as with human sera samples is reported

Fox, Roberta L.

doi: 10.1366/0003702844554909pmid: N/A

Direct-current plasma emission spectrometric analysis of platinum group metals in solutions from automobile catalyst shows significant enhancement of analyte values Addition of a lithium buffer does not remove the interference The only matrix constituents in these solutions were aluminum and magnesium, both of which were found to cause enhancement in the determination of platinum, palladium, and rhodium A buffer consisting of 3500 mg/L lithium and 2500 mg/L lanthanum removed the enhancement effect of both magnesium and aluminum on these metals 8-hydroxyquinoline also reduced the degree of interference due to aluminum, although not as efficiently as lanthanum, indicating that formation of compounds in the dc plasma is a possible source for the observed interference

Angleys, G; Mermet, J. M.

doi: 10.1366/0003702844554990pmid: N/A

Based on a previously published work, calculations of the minimum plasma gas flow rate for torch tubes of various dimensions have been performed Predicted minimum rates have been verified by experiment It is possible to sustain a discharge at 600 W and 6 L/min without reducing drastically the external size of the torch One of the main parameters in torch design is the various flow velocities The main influence on the plasma gas flow rate is provided by the space between the external and the intermediate tube A practical design is proposed and a comparison is made with the literature

Mitchell, J. W.; Herring, C; Bylina, E

doi: 10.1366/0003702844554963pmid: N/A

The viability and limitations of inductively coupled plasma atomic emission spectrometry (ICP-AES) for trace characterization of concentrated EDTA solutions are determined Qualitative detection of elemental impurities based on multielement scans, semiquantitative estimates of impurity levels obtained by comparison of results with calibration graphs in the 1 to 5 µg/mL range, and quantitative analyses via standard addition methods involving EDTA solutions doped with trace metals in the 01 to 10 µg/mL, and in the 001 to 016 µg/mL ranges are reported Applications of the method to the analysis of EDTA, purified by recrystallization, and to the monitoring of EDTA solutions, electrolyzed at the mercury cathode, are described Mercury cathode electrolysis is superior to the recrystallization method only in the case of removal of Cd, Cu, and Fe The recrystallization procedure provides the greater advantage of reducing the levels of a broader range of trace elements than was possible by electrolysis Both methods reduce amenable trace elemental impurities in EDTA solutions to the 100 ng/mL level or below

Huie, Carmen W.; Yeung, Edward S.

doi: 10.1366/0003702844554882pmid: N/A

A highly collimated laser beam is used to observe molecular absorption in a premixed air-acetylene flame by providing a two-dimensional image on a vidicon camera Spatially resolved molecular concentrations can thus be obtained in 1/60 second By measurement of the relative intensities of absorption from different vibrational levels in the ground state of the molecules, a vibrational temperature can be derived for each of the spatial regions in the flame This information is directly relevant to the understanding of dissociation in flames

Tyson, Lesia L.; Ling, Yong-Chien; Mann, Charles K.

doi: 10.1366/0003702844554972pmid: N/A

Two data-handling techniques, least-squares fitting and cross-correlation, have been used for three-component analysis under comparable conditions with the use of both simulated and real data Factors considered are the effect of variation in degree of peak overlap, signal-to-noise ratio, the effect of peak width variations when peak maxima occur at the same position, and the effect of varying peak intensities A series of lipid mixtures was analyzed by each method with the use of infrared absorption This permits comparison of these results with earlier reports Both least-squares and cross-correlation can be used with samples that are outside the applicable range of the earlier work In this comparison, the least-squares results are somewhat better than those from cross-correlation

Baraldi, Pietro; Fabbri, Gianfranco

doi: 10.1366/0003702844554954pmid: N/A

The IR emission spectra of a number of organic compounds have been examined in comparison with absorption spectra The behavior of band intensity as a function of some experimental parameters has been considered in order to find the optimum range of the parameters for the recording of the emission spectra It is shown that the spectra recorded on samples with low optical thickness and low crystal size are very close to absorption spectra Specific fields of application can be found where emission techniques exhibit some advantages in comparison with absorption ones

Azarraga, L. V.; Brackett, J. M.; Castles, M. A.; Rogers, L. B.

doi: 10.1366/0003702844554936pmid: N/A

A technique for the obtaining of the energy signal and, thus, the IR spectra is described The technique is simple and sensitive and allows the observation of high frequency vibrational bands The technique utilizes a silver bromide disc as a sample holder set in a diffuse reflectance attachment Spectra of o-nitroaniline 1-tetra-decanol, and copper phthalocyanine green are presented Possible applications of the technique include compound identification and FT-IR analysis of HPLC effluent