Sample introduction systems laser ablation method

Because ICP-MS with different instrumentations and sample introduction systems (besides solution nebulization, also laser ablation or hyphenated methods, such as HPLC, CE, SPME) is today the most frequently used analytical technique for precise and accurate isotope ratio measurements, the following section will mainly focus on this form of mass spectrometry with an inductively coupled plasma source. 

Use of inductively coupled plasma-mass spectrometry (1CP-MS) coupled to a laser-ablation sample introduction system (LA-ICP-MS) as a minimally destructive method for chemical characterization of archaeological materials has gained favor during the past few years. Although still a relatively new analytical technique in archaeology, LA-ICP-MS has been demonstrated to be a productive avenue of research for chemical characterization of obsidian, chert, pottery, painted and glazed surfaces, and human bone and teeth. Archaeological applications of LA-ICP-MS and comparisons with other analytical methods are described. 

The power of this MS technique has driven the development of methods to interface ICP/MS instruments with various sample introduction systems. Specialized sample introduction systems include ion chromatography (Seubert, 2001), gas chromatography (Vonderheide et al., 2002), and capillary electrophoresis (Costa-Fernandez et al., 2000). Other techniques are hydride generation (used to volatilize selected species and obtain some matrix/elemental separation) (Reyes et al., 2003) (Bings et al., 2002) laser ablation (Gonzalez et al., 2002 Heinrich et al., 2003 Russo et al., 2002), and electrothermal vaporization (Richardson, 2001 Vanhaecke and Moens, 1999). 

There are two principal means of sample introduction for isotopic analysis by MC-ICP-MS in geo- and cosmochemistry. Most common is the technique of solution nebulization, whilst laser ablation (LA) systems have been applied for in situ isotope ratio measurements [32]. As such, MC-ICP-MS complements both the TIMS and SIMS methodologies, which are the most common alterative methods for bulk sample and in situ isotopic analysis, respectively, in cosmochemical research. 

For laser ablation as a method of sample introduction for ICP-MS, sohd-state lasers are preferred, because for these systems an acceptable compromise between output laser parameters and system costs is obtained. Nevertheless, excimer lasers are also becoming more popular regardless of the high maintenance demands, since the outstanding beam profile characteristics and high-energy output they offer are attractive features for several analytical applications. In... 

Several other alternative calibration methods using aqueous standard solutions have been applied in the case that appropriate standard reference materials are not available. " Online solution-based calibration utilizes the introduction of mixed laser-ablated sample material together with nebulized standard solutions through desolvation units to the ICR Two setups are in use, based on adding the solutions either before (the so-called single gas flow system) or after (known as the dual gas flow system) the laser cell (see Figure 6.13). ° Using such a procedure, one can use either external standardization, analyte standard addition, or even isotope dilution techniques for small sample sizes. ... 

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