In ICPMS

All of these components are critical to the high sensitivity found in ICPMS instruments. Figure 1 shows their arrangement. 

The inductively coupled plasma and the torch used in ICPMS are similar to that used in ICP-OES. In ICPMS, the torch is aimed horizontally at the mass spectrometer, rather than vertically, as in ICP-OES. In ICPMS the ions must be transported physically into the mass spectrometer for analysis, while in ICP-OES light is trans-... 

The part that marries the plasma to the mass spectrometer in ICPMS is the interfacial region. This is where the 6000° C argon plasma couples to the mass spectrometer. The interface must transport ions from the atmospheric pressure of the plasma to the 10 bar pressures within the mass spectrometer. This is accomplished using an expansion chamber with an intermediate pressure. The expansion chamber consists of two cones, a sample cone upon which the plasma flame impinges and a skimmer cone. The region between these is continuously pumped. 

By for the most simple acid to work with in ICPMS is nitric acid. This has minimal spectral interferences and in concentradons under 5% does not cause excessive wear to the sample cones. Other acids cause some spectral interferences that often must be minimized by dilution or removal. When HF is used, a resistant sampling system must be installed that does not contain quartz. 

The role of the nebulizer in ICPMS is to transform the liquid sample into an aerosol. This is carried into the plasma by an ai on flow after passing through a... 

Detection limits in ICPMS depend on several factors. Dilution of the sample has a lai e effect. The amount of sample that may be in solution is governed by suppression effects and tolerable levels of dissolved solids. The response curve of the mass spectrometer has a large effect. A typical response curve for an ICPMS instrument shows much greater sensitivity for elements in the middle of the mass range (around 120 amu). Isotopic distribution is an important factor. Elements with more abundant isotopes at useful masses for analysis show lower detection limits. Other factors that affect detection limits include interference (i.e., ambiguity in identification that arises because an elemental isotope has the same mass as a compound molecules that may be present in the system) and ionization potentials. Elements that are not efficiently ionized, such as arsenic, suffer from poorer detection limits. 

Another type of interference in ICPMS is suppression of the formation of ions from trace constituents when a large amount of analyte is present. This effect depends on the mass of the analyte The heavier the mass the worse the suppression. This, in addition to orifice blockage from excessive dissolved solids, is usually the limiting factor in the analysis of dissolved materials. 

Full quantitation is accomplished in the same manner as for most analytical instrumentation. This involves the preparation of standard solutions and matching of the matrix as much as possible. Since matrix interferences are usually minimized in ICPMS (relative to other techniques), the process is usually easier. 

Montaser A, Minnich MG, McLean JA, Liu H, Caruso JA, McLeod CW (1998) Sample introduction in ICPMS. 

Turner IL, Montaser (1998) Plasma generation in ICPMS. In Inductively Coupled Plasma Mass Spectrometry. Montaser A (ed),. Wiley-VCH, New York, p 265-334... 

L. Moens and N. Jakubowski, "Double-Focusing Mass Spectrometers in ICPMS Anal. Chem. 1998, 70. 251A F. A. M. Planchon, C. F. Boutron,... 

Sources of errors that were detected were mainly due to calibration errors, high blanks explaining high results and uncontrolled interferences (e.g. in ICPMS). 

Ar-interferences with and " Fe were likely the cause for high standard deviations in ICPMS for potassium and iron, respectively. 

In the case of copper, spectral interferences in ICPMS were found, leading to high results which were probably caused by a spectral overlap from an unidentified polyatomic species at mass 65. The existence of this species was confirmed by a mass spectrum obtained by high resolution ICPMS, although its exact composition could not be determined. DPASV and CSV were in good agreement with the other techniques in this case. Provided that a proper destruction of organic matter be carried out, no problems were actually suspected for Cu. 

In ICPMS. matrix effects become noticeable at concomitant concentrations of greater than about 500 to 1000 mg/mL. Usually these effects cause a reduction... 

Like ICP mass spectra, spark source mass spectra are much simpler than atotnic emission spectra, consisting of one major peak for each isotope of an element as well as a few weaker lines corresponding to multiply charged inns and ionized oxide and hydroxide species. The presence of these additional ions creates the potential for interference just as in ICPMS. 

What types of mass spectrometers are used in ICPMS How do they differ from one another ... 

What function does the K P torch have in ICPMS ... 

Relatively new innovations in ICPMS instrumentation may partly alleviate some of those limitations. For example, some ICPMS instruments are now available with a magnetic sector mass spectrometer rather than a quad-rupole mass spectrometer. These new instruments may provide increased accuracy and precision of lead isotope ratio measurements, which would lead to higher quality measurements by isotope dilution. 

Sea water and other saline waters pose some problems for the atomization methods. Nebulizers for the ICP tend to become blocked with salt encrustations with a disastrous effect on sensitivity. This can be overcome in direct analysis by flow injection techniques, or by the use of high-solids nebulizers. Dilution also helps here but, of course, degrades the detection limits. The sampling cone in ICPMS equipment is also prone to be gradually occluded when... 

Campbell, M.J., and Toervenyi, A. (1999). Non-spectroscopic suppression of zinc in ICPMS in a candidate biological reference material (IAEA 392 Algae).Anal. At. Spectrom. 14(9), 1313. 

Moens, L., and Jakubowski, N. (1998). Double-focusing mass spectrometers in ICPMS— From its very first days, the Achilles heel of inductively coupled plasma MS has been the number of spectroscopic and nonspectroscopic interferences. The only general method to overcome this limitation is to go to high mass resolution with a double-focusing instrument. Anal. Chem. 70(7), 251 A. 

Peters, G. R., and Beauchemin, D. (1993). Characterization of an interface allowing either nebulization or gas chromatography as the sample introduction system in ICPMS. Anal. Chem. 65(2), 97. 

Moens, L. and Jakubowski, N. (1998) Double-focusing mass spectrometers in ICPMS. Anal Chem. News Features, 70(7), 251A-256A... 

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