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Multi-channel dilution analysis (MCDA) is a new calibration method that performs multiple dilutions of a standard solution as it makes its way from an autosampler to an analytical instrument. MCDA is based on the standard dilution analysis (SDA) method that combines the traditional standard additions and internal standardization calibration methods, correcting for both matrix interferences and fluctuations in signal levels associated with variations in the sample environment. Analysts operate the instrument in the normal manner, as all dilutions are performed automatically by splitting the sample stream entering the instrument into multiple channels of different tubing diameters and lengths. This setup results in a signal "stairstep" as portions of solution are measured at different points in time. A calibration curve is prepared from the plateau regions of the signal stairstep. MCDA has been exhibited using inductively coupled plasma optical emission spectrometry, which is a workhorse for the determination of trace metals in solution. However, MCDA is applicable for any analyte of interest in any sample type, as long as the selected measurement technique accepts samples as a flowing liquid stream. MCDA is applied to the analysis of three certified reference materials by inductively coupled plasma optical emission spectrometry (ICP-OES). Percent recoveries for a suite of analytes range from 87--106%, with relative standard deviations on the order of 1%. MCDA simplifies the analysis process, increasing sample throughput by significantly decreasing the time required for solution preparation. [ABSTRACT FROM AUTHOR]

Lithium isotopic ratios have wide ranging applications as chemical signatures, including improved understanding of geochemical processes and battery development. Measurement of isotope ratios using optical spectroscopies would provide an alternative to traditional mass spectrometric methods, which are expensive and often limited to a chemical laboratory. Raman spectra of 7Li2CO3, 6Li2CO3, 7LiOH*H2O, and 6LiOH*H2O have been measured to determine the effect of lithium isotope substitution on the Raman molecular vibrations. Thirteen peaks were observed in the spectrum of lithium carbonate, with discernable isotopic shifts occurring in eleven of the 13 vibrations, two of which have not been previously reported in the literature. The spectrum of lithium hydroxide monohydrate contained nine peaks, with discernable isotopic shifts occurring in eight of the nine vibrations, four of which have not been previously reported in the literature. The Raman spectral data reported here for lithium carbonate and lithium hydroxide monohydrate are in agreement with the previously reported works in the literature, in which the Raman active modes of these molecules were first identified and assigned. However, due to the stability and resolution of the detection system used in this work, isotopic shifts with a magnitude less than one wavenumber have been identified. Principal component regression was used to evaluate the sensitivity to isotopic content of small Raman peak shifts in Li2CO3 and indicates differences greater than 2 atom% could be reliably determined. These measurements add to the body of work on lithium isotope Raman spectroscopy for these two compounds and increases the number of Raman bands which could be used for lithium isotope content analysis. Graphical Abstract [ABSTRACT FROM AUTHOR]

This work reports an investigation on the feasibility of using a photomultiplier tube (PMT) to follow the time evolution of self-absorption of copper resonance transitions at 324.7 nm and 327.4 nm. The plasma was obtained by focusing a Nd:YAG laser, operated at 1064 nm, on a series of aluminum alloy standard disks containing different copper concentrations. The results described have been obtained at different times and with different set-ups. These set-ups consisted of a Paschen-Runge polychromator, a LIBS 2000 spectrometer, and a spectrometer equipped with both an intensified chargecoupled device (ICCD) and PMT. Both PMT signals and time-resolved spectra were obtained and the ratio of the two Cu resonant lines was calculated, compared, and discussed. By selecting different delay times and integration gates of the PMT signals, the self-absorption effect of the Cu resonant lines was found to be changing, implying that, by careful selection of the integration window of PMT signals, the self-absorption may be minimized, thus improving the calibration linearity of the technique. [ABSTRACT FROM AUTHOR]

This work reports an investigation on the feasibility of using a photomultiplier tube (PMT) to follow the time evolution of self-absorption of copper resonance transitions at 324.7 nm and 327.4 nm. The plasma was obtained by focusing a Nd:YAG laser, operated at 1064 nm, on a series of aluminum alloy standard disks containing different copper concentrations. The results described have been obtained at different times and with different set-ups. These set-ups consisted of a Paschen-Runge polychromator, a LIBS 2000 spectrometer, and a spectrometer equipped with both an intensified charge-coupled device (ICCD) and PMT. Both PMT signals and time-resolved spectra were obtained and the ratio of the two Cu resonant lines was calculated, compared, and discussed. By selecting different delay times and integration gates of the PMT signals, the self-absorption effect of the Cu resonant lines was found to be changing, implying that, by careful selection of the integration window of PMT signals, the self-absorption may be minimized, thus improving the calibration linearity of the technique.