Quadrupole ICP-MS

Esser and Volpe [958,959] used a shipboard single-collector quadrupole ICP-MS to survey surface barium and toxic metal levels in seawater. 

Figure 9.2 Schematic diagram of a quadrupole ICP-MS capable of working in either the solution or laser ablation mode. In the solid mode, a vertical laser ablates material from the sample which is mounted on a moveable horizontal stage. In solution mode, the liquid is sucked up into the injection chamber.

These comments apply to the running of a low resolution quadrupole ICP-MS, capable of both solution and laser ablation analysis, since this is the most widespread form of the instrument. High resolution MC ICP-MS is, as they say, a whole other ball game ... 

Due to the non-linear geometry of all sector field instruments (ICP-SFMS see Figure 5.1, right column, at the bottom) the instrumental background is about one order of magnitude better (0.1-0.5 cps) than in quadrupole ICP-MS. 

As an alternative to commercial quadrupole based ICP-MS measurements at low mass resolution ( / 300), in 1996 Yiang and Douglas15 proposed a quadrupole ICP-MS system which allows a maximum mass resolution of 9000. At a mass resolution of 5000 the sensitivity was comparable to that of a commercial double-focusing sector field ICP-MS operated at the same mass resolution. Due to the very high continuum instrumental background of about lOOOcps no commercial high resolution quadrupole instrumentation with an inductively coupled plasma source exists and the development of high resolution quadrupole based ICP-MS has ceased. 

The axial time-of-flight ICP-MS was introduced in 1998 by LECO (Renaissance, LECO, St. Joseph, MI) and has been commercially available for several years. A schematic of the ICP-ToF-mass spectrometer is shown in Figure 5.11. The analytical performance of this mass spectrometer, which allows 25 000 spectra to be measured per second and is thus faster than a quadrupole ICP-MS,... 

The sensitivities of elements measured by ICP-MS on standard solutions nebulized with an ultrasonic nebuhzer (USN) are roughly 5000 times higher than in LA-ICP-MS when analyzing a fused lithium borate target of geological standard (NIM-G) by quadrupole ICP-MS Elan... 

Numerous applications of quadrupole ICP-MS (without a collision cell) for isotope ratio measurements can be found in quite different fields. For example, magnesium isotope ratios on... 

The introduction of the collision cell in ICP-MS represents progress in ICP-MS instrumentation which is relevant for improving the precise determination of isotope ratios in comparison to commercial quadrupole ICP-MS without a collision cell. The first investigation of the basic principles and application of the collision cell to improve sensitivity in inorganic ultrasensitive mass spectrometry was published 24 years ago by Becker and Dietze.115... 

In addition, there exist a multitude of different applications in water analysis by ICP-MS for environmental control. For example, Lawrence et cdP determined rare earth element concentrations in natural waters (these are river, lake, sea or groundwater) by quadrupole ICP-MS using external calibration and employed river water reference material SLRS-4 to validate the analytical data. The speciation of yttrium and lanthanides in water samples by SEC-ICP-MS was studied by Haraguchi et a/.18 whereby the detection of La, Ce and Pr corresponded to the occurrence of large organic molecules. 

Henry et al.33 reported that improvements in quadrupole ICP-MS resulted in ag mass detection capability. Consequently the analysis of radionuclides with shorter half-lives is also possible. In Table 9.38 the detection limits of several mass spectrometric techniques for the determination of long-lived radionuclides are compared. 

Joannon and Pin.50 A low detection limit was achieved in quadrupole ICP-MS when the pressure in the interface was reduced from approx. 2 to 0.85 mbar. Lariviere et al.51 developed a selective extraction procedure for the preconcentration of 226Ra from uranium ores and biological samples. The measurements were performed by ICP-QMS with a hexapole collision cell in order to reduce possible interferences. An absolute detection limit of 0.02 fg (0.75 mBq) was obtained using less than 4 mg of solid sample or 25 ml of liquid sample. 

Since the launch of the first commercial quadrupole ICP-MS instrument in 1983, the technology has evolved from large, floor-standing, manually operated systems, with limited functionality and relatively poor detection limit capabilities, to compact, sensitive and highly automated routine analytical instruments. In principle, all ICP-MS systems consist of similar components a sample introduction system, the ICP ion source, an interface system, the mass analyser, the detector and a vacuum system [8,11]. 

More recently, the advent of the collision/reaction cell technology has revolutionised commercial quadrupole ICP-MS systems. A gas, such as hydrogen, helium or ammonia, is introduced into the reaction cell (placed inside the mass spectrometer and preceding the analyser quadrupole), where it reacts and dissociates or neutralises the polyatomic species or precursors. Through collision and reaction with appropriate gases in a cell, interferences... 

Epov, V. N., Evans, R. D., Zheng, J., Donard, O. F. X., and Yamada, M., Rapid fingerprinting of Pu-239 and Pu-240 in environmental samples with high U levels using online ion chromatography coupled with high-sensitivity quadrupole ICP-MS detection, J. Anal. At. Spectrom., 22, 1131-1137, 2007. 

When sector-based mass spectrometers are used in a low-resolution mode the sensitivity can be higher than attainable with current quadrupole mass spectrometers. Random background count rates are also typically lower for sector-based mass spectrometers. As a result, detection limits are one to two orders of magnitude better than for typical quadrupole ICP-MS instruments. 

Platinum-based compounds are commonly used as cancer treatment agents. Pharmacokinetic studies of these antitumor drugs require ultratrace analysis. Electrothermal vaporization ICP-MS provides low detection limits for small samples [256]. High-performance liquid chromatography with ICP-MS detection allows speciation of platinum compounds in tissues [256]. LA-ICP-MS can be used to study the distribution of platinum in tissues and tumors [256]. Natural levels of Pt are below typical quadrupole ICP-MS detection limits [257]. 

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