Inductively coupled plasma mass resolution

Method abbreviations D-AT-FAAS (derivative flame AAS with atom trapping), ETAAS (electrothermal AAS), GC (gas chromatography), HGAAS (hydride generation AAS), HR-ICP-MS (high resolution inductively coupled plasma mass spectrometry), ICP-AES (inductively coupled plasma atomic emission spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), TXRF (total reflection X-ray fluorescence spectrometry), Q-ICP-MS (quadrapole inductively coupled plasma mass spectrometry)... 

ICP-MS (inductively coupled plasma mass spectrometry) is frequently used for determining ultratrace amounts of technetium [9]. In spite of the high cost of the equipment, this detection method is far superior to other radiometric methods as regards sensitivity. When a double focussing high-resolution system is used (HR-ICP-MS) and an ultrasonic nebulizer is introduced [10], the detection limit is in the order 0.002 mBq. The ICP-MS method has been successfully applied to the determination of environmental "Tc as well as to other long-lived radionuclides of neptunium and plutonium in the environment. 

Inductively coupled plasma mass spectrometry is now such an important technique in archaeology, as elsewhere, that we devote a whole chapter to it. There are now a number of different ICP MS modes of operation (solution analysis, laser ablation, multicollector, high resolution) this chapter provides a general overview. Further description of the instrumentation for ICP MS may be found in Harris (1997) and Montaser (1998). Some general applications of solution ICP MS are discussed by Date and Gray (1989), Platzner (1997), and Kennett et al. (2001). 

Turner PJ, Mills DJ, Schroder E, Lapitajs G, Jung G, lacone LA, Haydar DA, Montaser A(1998) Instrumentation for low- and high-resolution ICPMS. In Inductively Coupled Plasma Mass Spectrometry. Montaser A (ed), Wiley-VCH, New York, p 421-501... 

Table 5.2 Summary of selected analytical methods for molecular environmental geochemistry. AAS Atomic absorption spectroscopy AFM Atomic force microscopy (also known as SFM) CT Computerized tomography EDS Energy dispersive spectrometry. EELS Electron energy loss spectroscopy EM Electron microscopy EPR Electron paramagnetic resonance (also known as ESR) ESR Electron spin resonance (also known as EPR) EXAFS Extended X-ray absorption fine structure FUR Fourier transform infrared FIR-TEM Fligh-resolution transmission electron microscopy ICP-AES Inductively-coupled plasma atomic emission spectrometry ICP-MS Inductively-coupled plasma mass spectrometry. Reproduced by permission of American Geophysical Union. O Day PA (1999) Molecular environmental geochemistry. Rev Geophysics 37 249-274. Copyright 1999 American Geophysical Union...

The samples purified with lEC were diluted to approximately 100 ppb Cu. These samples were injected into a Multicollector Inductively-Coupled-Plasma mass spectrometer (MC-ICPMS, Micromass Isoprobe at the University of Arizona and Neptune at Washington State University) in low resolution mode using a microconcentric nebulizer to increase sensitivity for the samples with lower concentrations of copper. The nebulizer flow was adjusted so that the intensity of the Cu beam remained constant at 2 volts. Both on and off peak blank corrections were applied to the data and yielded the same result. 

Cations were determined by high-resolution inductively coupled plasma-mass spectrometry (HR-ICPMS), relatively new analytical instrumentation with a large dynamic range and detection limits (DLs) in the low (1-50) parts per trillion (ppt) for most elements. The exceedingly low DLs allow for recognition of elemental variations that are not possible with traditional analytical methods for water. 

In inductively coupled plasma-mass spectrometry, isobaric interference occurs between species with the same mass and charge. Interference can be eliminated if the mass spectral resolution is sufficiently great or by dissociating an interfering polyatomic species with a collision cell. When laser ablation is used to sample a solid, matrix-matched standards are often necessary for quantitative analysis. 

Several other microanalytical methods in common use potentially have application on soil and sediments section samples. Laser-ablation inductively coupled plasma mass spectrometery (LA-ICP-MS) has been used on soil thin-sections from a controlled field experiment (21) but required special resins in the preparation. There is presently (May 2006) no reported use of this method on archaeological soil samples. Likewise, for extremely fine-resolution studies (i.e. <10 pm) with low minimum detection limits and despite difficult calibration, secondary ion microscopy (SIMS) has a potential role in examining archaeological soil thin sections. At even higher lateral resolutions ( 100 nm) Auger electron spectroscopy (AES) could also be considered for surface (<5 nm deep) analyses. At present however, the use of these methods in soil systems is limited. SIMS has been focused on biochemical applications (22), whereas AES... 

Kim, C. S., Kim, C. K., Lee, J. I., and Lee, K. J., Rapid determination of Pu isotopes and atom ratios in small amounts of environmental samples by an on-line sample pretreatment system and isotope dilution high resolution inductively coupled plasma mass spectrometry, J. Anal. At. Spectrum., 15, 247-255, 2000. 

Several groups have studied the determination of "technetium in environmental samples including soil. High-resolution inductively coupled plasma mass spectrometry [23,24] was used in these studies. In one study "technetium was eluted from the soil by nitric acid and the analyte was separated by three solvents using 30% trioctylamine, methylethylketone and cyclohexanone [23]. Purification of the "techretium extract was performed by using an anion... 

Multi-element determination of dissolved metals at ultratrace level may be performed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). U.S. EPA s Methods 200.8 and 1638 present a methodology for measuring trace elements in waters and wastes by the above technique. Sample is acid digested and the solution is introduced by pneumatic nebulization into a radio-frequency plasma. The elements in the compounds are atomized and ionized. The ions are extracted from the plasma through a differentially pumped vacuum interface and separated by a quadrupole mass spectrometer by their mass to charge ratios. The mass spectrometer must have a resolution capability of 1 amu peak width at 5% peak height. 

Evans, E. H. Wolff, J.-C. Eckers, C. 2001. Sulfur-specific detection of impurities in cimetidine drug substance using liquid chromatography coupled to high resolution inductively coupled plasma mass spectrometry and electrospray mass spectrometry. Anal. Chem., 73,4722-4728. 

Mass Resolution Required to Resolve Common Spectral Interferences Encountered in Inductively Coupled Plasma Mass Spectrometry... 

MASS RESOLUTION REQUIRED TO RESOLVE COMMON SPECTRAL INTERFERENCES ENCOUNTERED IN INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY... 

The table below lists some common spectral interferences that are encountered in inductively coupled plasma mass spectrometry (ICP-MS), as well as the resolution that is necessary to analyze them.1 The resolution is presented as a dimensionless ratio. As an example, the relative molecular mass (RMM) of the polyatomic ion 15N160+would be 15.000108 + 15.994915 = 30.995023. This would interfere with 31P at a mass of 30.973762. The required resolution would be RMM/8RMM, or 30.973762/0.021261 = 1457. One should bear in mind that as resolution increases, the sensitivity decreases with subsequent effects on the price of the instrument. Note that small differences exist in the published exact masses of isotopes, but for the calculation of the required resolution, these differences are trivial. Moreover, recent instrumentation has provided rapid, high-resolution mass spectra with an uncertainty of less than 0.01%. 

Montes-Bayon, M., B Hymer, C., Ponce de Leon, C., and Caruso, J.A. 2001. Resolution of seleno-amino acid optical isomers using chiral derivatization and inductively coupled plasma mass spectrometric (ICP-MS) detection. J. Anal. At. Spectrom. 16(9), 945-950. 

C. F. Harrington, S. Elahi, S. A. Merson, P. Ponnampalavanar, Quantitative analysis of iron-containing protein myoglobin in different foodstuffs by liquid chromatography coupled to high-resolution inductively coupled plasma mass spectrometry, J. AOAC Int., 87 (2004), 253 D258. 

N. M. Reed, R. O. Cairns, R. C. Hutton, Y. Takaku, Characterisation of polyatomic ion interferences in inductively coupled plasma mass spectrometry using a high resolution mass spectrometer, J. Anal. Atom. Spectrom., 9 (1994) 881-897. 

I. Rodushkin, T. Ruth, D. Klockare, Non-spectral interferences caused by a saline water matrix in Q and high resolution inductively coupled plasma mass spectrometry, J. Anal. Atom. Spectrom., 13 (1998), 159-166. 

Bechmann, I.E., Stiirup, S., Kristensen, L.V. High resolution inductively coupled plasma mass spectrometry (HR-ICPMS) determination and multivariate evaluation of 10 trace elements in mussels from 7 sites in Limfjorden, Denmark. Fresenius J. Anal. Chem. 368, 708-714 (2000)... 

Jakubowski, N., Thomas, C., Klueppel, D., Stuewer, D. Speciation of metals in biomolecules by use of inductively coupled plasma mass spectrometry with low and high mass resolution. Analysis 26, M37-M43 (1998)... 

As noted earlier, USNs have been employed for sample insertion into atomic spectrometers suoh as flame atomio absorption spectrometry (FAAS) [9,10], electrothermal atomic absorption speotrometry (ETAAS) [11], atomic fluorescence spectrometry (AFS) [12,13], induotively ooupled plasma-atomic emission spectrometry (ICP-AES) [14,15], inductively coupled plasma-mass spectrometry (ICP-MS) [16,17] and microwave induced plasma-atomic emission spectrometry (MIP-AES) [18,19]. Most of the applications of ultrasonic nebulization (USNn) involve plasma-based detectors, the high sensitivity, selectivity, precision, resolution and throughput have fostered their implementation in routine laboratories despite their high cost [4]. 

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