Inductively coupled plasma isotope mass discrimination

Taylor PDF, De Bievre P, Walder AJ, Entwistle A (1995) Vahdation of the analytical linearity and mass discrimination correction model exhibited by a Multiple Collector Inductively Coupled Plasma Mass Spectrometer by means of a set of synthetic uranium isotope mixtures. J Anal At Spectrom 10 395-398... 

Hirata, T. (1996) Lead isotopic analyses of NIST standard reference materials using multiple collector inductively coupled plasma mass spectrometry with a modified external correction method for mass discrimination effect. Analyst 121, 1407-1411. 

Laser-ablation, inductively coupled-plasma mass spectrometry (LA-ICPMS) is an instrumental technique in which a laser-ablahon cell and ophcal microscope supplant the spray chamber/nebulizer apparatus of a standard ICP-MS instrument. Subsamples of questioned material are ablated from a solid sample via laser (often a pulsed Nd-YAG tuned to 266 or 213 nm). Ablated specimens are transported in a stream of Ar to a plasma torch for ionization and mass discrimination as per solution ICP-MS. Only minimal sample prep is required, and few restrictions are placed on the nature of questioned solid samples (Brundle et al. 1992 Vickerman 1998). While laser spot sizes can be reduced to several micrometers, sensitivity is degraded as a result, and usual spatial resolutions are on the order of 10-100 pm. Matrix-matched standards are also necessary for accurate trace-element and isotopic quantitative analyses in LA-ICPMS. Depending on the quality of such primary standards, LA-ICPMS accuracies are typically 1-10%, with limits-of-detection in the parts-per-billion (ppb) range (O Table 62.1). 

Van Es et al. [92] discuss the discrimination of document (multiuse office) paper utilizing IRMS alongside a complement of other techniques, including X-ray fiuo-rescence spectrometry (XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The carbon, hydrogen, and oxygen isotope values of 25 different samples were measured, where 21 of the 25 paper samples could be discriminated, utilizing the IRMS technique alone. Full discrimination was achievable when the technique was used in conjunction with XRF or LA-ICP-MS. 

Resano, M., Marzo, R, Pdrez-Arantegui, J., Aramendfa, M., Cloquet, C, Vanhaecke, F. (2008) Laser ablation-inductively coupled plasma-dynamic reaction cell-mass spectrometry for the determination of lead isotope ratios in ancient glazed ceramics for discriminating purposes. Journal of Analytical Atomic Spectrometry, 23(9), 1182-1191. 

Correction of Instrumental Mass Discrimination for Isotope Ratio Determination with Multi-Collector Inductively Coupled Plasma Mass Spectrometry... 

Gallon, C., Aggarwal, J., and Flegal, A.R. (2008) Comparison of mass discrimination correction methods and sample introduction systems for the determination of lead isotopic composition using a multicoHector-inductively coupled plasma mass spectrometer. Anal. Chem., 80, 8355-8363. 

In all these applications, isotope ratio data are produced, which are interpreted on an absolute or relative basis and which have an impact on our daily life, whether this is in science (e.g., age of an artifact), in society (e.g., provenance of food), or in public safety (e.g., neutron shielding in nuclear power plants). To ensure that these data are reliable and accurate, some specific requirements have to be fulfilled. The main requirement is that all these measurement results are comparable, which means that the corresponding results can be compared and differences between the measurement results can be used to draw further conclusions. This is only possible if the measurement results are traceable to the same reference [25]. This in turn can only be realized by applying isotopic reference materials (IRMs) for correction for bias and for validation of the analytical procedure. Whereas in earlier days only experts in mass spectrometry were able to deliver reproducible isotope ratio data, nowadays many laboratories, some of which may even have never been involved with mass spectrometry before, produce isotope ratio data using inductively coupled plasma mass spectrometry (ICP-MS). Especially for such users, IRMs are indispensable to permit proper method validation and reliable results. The rapid development and the broad availability of ICP-MS instrumentation have also led to an expansion of the research area and new elements are under investigation for their isotopic variations. In this context, all users require IRMs to correct for instrumental mass discrimination or at least to allow isotope ratio data to be related to a commonly accepted basis. 

Accuracy and long-term reproducibility of lead isotopic measurements by multipleinductively coupled plasma mass spectrometry using an external method for correction of mass discrimination. Int. J. Mass Spectrom., 181,123-133. 

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