Ablation - Plasma Source Spectrometry

Solid sampling with a NdiYAG laser for direct analysis with ICP-AES using an echelle optical system in conjunction with a solid-state detector is a straightforward technique [70]. 

Success of sample introduction methods, such as LA, ETV or LC in combination with ICP-MS, is on account of tandem source mass spectrometry [71], Instead of one source being responsible for the vaporisation, atomisation and ionisation of the sample, these tasks are divided among two different sources (i) LA/ETV vaporisation (and atomisation) (ii) ICP (atomisation and) ionisation and (Hi) MS identification and quantification. 

LA-ICP-MS suffers from ablation-, transport-and excitation-induced elemental fractionation. For quantitative analysis there are at least three principle 

Advantages of LA-ICP-MS compared to XRF are better detection limits, simpler spectra and higher sensitivity for the light elements but application of the method is often hampered by absence of suit-abie standard reference materials. The method compares favourably with the electron microprobe, because of its low detection limits and wide range of elements from Li to U measurable. Very good agreement was achieved between the laser ablation results and the values determined by NAA, at the low ppm level [77]. A precision of ca. 10% was 

Mitchell et al. [80] have described development of a laser ablation/direct-current argon plasma (DCP) emission spectrometry system based on a relatively low-energy, high-repetition rate Nd YAG laser as opposed to the high-energy and low-repetition rate ruby lasers. 

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Gray AL (1985). Solid sample introduction by laser ablation for inductively coupled plasma source mass spectrometry. Analyst 110 551-556... 

Jackson SE, Gunther D (2003) The nature and sources of laser induced isotopic fractionation in laser ablation-multicollector-inductively coupled plasma-mass spectrometry. J Anal At Spectrom 18 205-212 Jiang S-J, Houk RS, Stevens MA (1988) Alleviation of overlap interferences for determination of potassium isotope ratios by Inductively-Coupled Plasma Mass Spectrometry. Anal Chem 60 1217-1220 Lam JWH, Horlick G (1990) A comparison of argon and mixed gas plasmas for inductively coupled plasma-mass spectrometry. Spectrochim Acta Part B 45 1313-1325 Langmuir I, Kingdon KH(1925) Thermionic effects caused by vapours of alkali metals. Phil Trans R Soc A107 61-79... 

With the advent of multiple-collector inductively coupled plasma-source mass spectrometry (MC-ICPMS) it is now possible to measure Mg/ Mg and Mg/ Mg of Mg in solution with a reproducibility of 30 to 60 ppm or better (Galy et al. 2001). What is more, ultraviolet (UV) laser ablation combined with MC-ICPMS permits in situ analysis of Mg-bearing mineral samples with reproducibility of 100 to 200 ppm (Yoimg et al. 2002a). These new analytical capabilities allow mass-dependent fractionations of the isotopes of Mg to be used as tracers in natural systems. 

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. 

Since the mid-1960s, a variety of analytical chemistry techniques have been used to characterize obsidian sources and artifacts for provenance research (4, 32-36). The most common of these methods include optical emission spectroscopy (OES), atomic absorption spectroscopy (AAS), particle-induced X-ray emission spectroscopy (PIXE), inductively coupled plasma-mass spectrometry (ICP-MS), laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray fluorescence spectroscopy (XRF), and neutron activation analysis (NAA). When selecting a method of analysis for obsidian, one must consider accuracy, precision, cost, promptness of results, existence of comparative data, and availability. Most of the above-mentioned techniques are capable of determining a number of elements, but some of the methods are more labor-intensive, more destructive, and less precise than others. The two methods with the longest and most successful histoty of success for obsidian provenance research are XRF and NAA. 

Hi) Methods based on mass spectrometry Spark-source mass spectrometry Glow-discharge mass spectrometry Inductively coupled-plasma mass spectrometry Electro-thermal vaporization-lCP-MS Thermal-ionization mass spectrometry Accelerator mass spectrometry Secondary-ion mass spectrometry Secondary neutral mass spectrometry Laser mass spectrometry Resonance-ionization mass spectrometry Sputter-initiated resonance-ionization spectroscopy Laser-ablation resonance-ionization spectroscopy... 

Barba and his colleagues sampled the three outcrops of limestone to determine their distinctive signatures. This information was compared to lumps of calcium carbonate found in the finished plaster in the city. The group of scientists used several different techniques to examine the samples. The major element composition of the geological samples was determined by XRF. The major element composition of the lumps was determined by SEM-EDS. Trace element composition was determined by LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry) to measure the elemental composition of the plaster and the limestone. This methodology is well suited for analyses of very small lumps with microscopic spot sizes. The LA-ICP-MS method is able to analyze a large number of trace and rare earth elements with speed, precision, and high resolution, especially in cases where the major chemical composition does not appear to be particularly distinctive. The instrument worked extremely well for the characterization and determination of the provenance of the Ume plaster source material. 

Okuda T, Kato J, Mori J, Tenmoku M, Suda Y, Tanaka S, He KB, Ma YL, Yang F, Yu XC, Duan FK, Eei Y (2004) Daily concentrations of trace metals in aerosols in Beijing, China, determined by using inductively coupled plasma mass spectrometry equipped with laser ablation analysis, and source identification of aerosols. Sci Total Environ 330 145-158... 

D. B. Aeschliman, S. J. Bajic, J. Stanley, D. Baldwin, and R. S. Houk, Multivariate pattern matching of trace elements in solids by laser ablation inductively coupled plasma-mass spectrometry source attribution and preliminary diagnosis of fractionation, Anal. Chem. 76, 3119-3125 (2004). 

Peacock,E.,Neff, H., Rafferty,I,Meaker,T. (2007) Using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to source shell in shell-tempered pottery a pilot study from North Mississippi. Southeastern Archaeology, 26, 319-329. 

Arrowsmith, P (1990) Applications of laser ablation elemental analysis of sohds by secondary plasma source mass spectrometry. In Lasers and Mass Spectrometry, edited by Lubman, D.M. New York Oxford University... 

The corabination of an inductively coupled plasma ion source and a magnetic sector-based mass spectrometer equipped with a multi-collector (MC) array [multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS)] offers precise and reliable isotope ratio data for many solid elements. In fact, MC-ICP-MS provides data, the trueness (accuracy) and precision of which is similar to, or, in some cases, even superior to, that achieved by thermal ionization mass spectrometry (TIMS), considered the benchmark technique for isotope ratio measurements of most solid elements [1], The basic strength of ICP-MS lies in the ion source, which achieves extremely high ionization efficiency for almost all elements [2, 3]. Consequently, MC-ICP-MS is likely to become the method of choice for many geochemists, because it is a versatile, user-friendly, and efficient method for the isotopic analysis of trace elements [4-8], The ICP ion source also accepts dry sample aerosols generated by laser ablation [9-16], The combination of laser ablation (LA) with ICP-MS is now widely accepted as a sensitive analytical tool for the elemental and isotopic analysis of solid samples. 

The relation between acoustic and optical signals produced at UV-LA-ICP-AES spectrometry was discussed [81]. Moenke-Blankenburg [38] has described laser ablation for solid sample introduction for inorganic analysis. Arrowsmith [82] and Durrant [82a] have reviewed laser-assisted elemental analysis of solids by secondary plasma source mass spectrometry. 

Becker, J.S. Zoriy, M. Becker, J.S. Pickhardt, C. Przybylski, M. Determination of Phosphorus and Metals in Human Brain Proteins After Isolation by Gel Electroi oresis by Laser Ablation Inductively Coupled Plasma Source Mass Spectrometry. J. Anal. Atom. Spectrom. 2004,19, 149-152. 

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