International Journal of Mass Spectrometry 286 (2009) 95–97 Contents lists available at ScienceDirect International Journal of Mass Spectrometry journal homepage: www.elsevier.com/locate/ijms Lead–Lead Method for age dating of granitic sample by LA-ICP-MS A.M. Rashad ∗ , W.A. Ghaly, N.F. Zahran, A.I. Helal Central Laboratory for Elemental and Isotopic Analysis, N. R. C., Atomic Energy Authority, Abo Zaabal, Kalubia 13759, Egypt article info Article history: Received 4 May 2009 Received in revised form 30 June 2009 Accepted 6 July 2009 Available online 14 July 2009 Keywords: LA-ICP-MS Pb isotopic ratio Age dating abstract Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) is used for the direct analysis of Egyptian granite samples, which are collected from the eastern desert—Egypt for the determination of Pb isotopic ratios. The age of the samples is calculated using Lead–Lead Method. Standard Reference Material (SRM 981) is used for the mass bias correction. The probability of interferences is discussed and considered. The obtained age is found 498.56 ± 4.38 My after the mass bias correction. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Lead has four naturally occurring isotopes 204 Pb (1.4%), 206 Pb (24.1%), 207 Pb (22.1%) and 208 Pb (52.3%), three of which are radio- genic decay products of either uranium or thorium. The fourth, 204 Pb, has a very long half-life such that it may be considered ‘stable’ on a geological time scale. For this reason, in geological applica- tions, Pb isotopes are frequently ratioed to 204 Pb for comparative purposes. A number of applications concerning the determination of Pb isotope ratios in geological samples have been published. Both the peak hopping and scanning modes of measurement have been used with some success. Despite the wide range, often contradictory observations are made in the literature [1]. Isotope ratios are generally determined by means of thermal ion- ization mass spectrometry (TIMS) because of the excellent precision attainable (RSD values <0.05%). However, the extensive sample pre- treatment requirements led to some limitations in the routine use of TIMS in geochemical and archaeological research. Another development is that an ICP ion source coupled to a magnetic sector analyzer and multi-collector is now comercially available. Compared with TIMS, this provides much better sensi- tivity for elements with high thermal ionization energies [2], the ion beams do not undergo progressive mass fractionation, so that a simple correction may be made for mass bias using for example Tl to correct Pb mass bias [3]. In situ, spatially resolved analysis is available using a laser to ablate sample into the plasma [4]. ∗ Corresponding author. Tel.: +20 105 656233; fax: +20 244 691749. E-mail address: rashad119@yahoo.com (A.M. Rashad). Since 1990, ICP-MS has also been used for lead isotope stud- ies of archeological objects, such as various lead artefacts [5], ancient plumbic cosmetic pigments [6], brass baptismal fonts [7] and bronze or copper cast objects [8]. Although ICP-MS shows an inferior precision in comparison with TIMS, it has some important advantages, such as, its simple sample pre-treatment, higher sam- ple throughput and simple sample introduction and its widespread availability. In addition, previous work has shown that with a double focusing sector field ICP mass spectrometer operated at the low resolution setting [R = 300), isotope ratio precisions can reach the order of ≤0.05% RSD [9,10]. The improvement in precision observed with a sector field instrument operated at the lowest resolution setting can mainly be attributed to the flat-top shape of the peaks. In the framework of provenance studies, the precision obtained is sufficient to determine whether lead isotope fields show mutual overlap and is, hence, potentially useful. Finally with multiple col- lector ICP-MS, precision levels of 0.01% can be considered routine [3]. Precision can also be achieved with ICP-MS using multiple ion collectors (MC-ICP-MS) [11–13]. Amr et al. [14] measured the trace elements in irradiated gran- ite samples from Hiroshima by Laser Ablation Inductively Coupled Plasma Mass Spectrometry. Imai [15] described a direct quantitative analysis method of rocks (granite, basalt, andesite, rhyorite, gabbro) by LA-ICP-MS and reported that the signal intensity was normalized either by the ablated weight or the barium signal intensity. LA-ICP-MS is increasingly used in different fields of modern sci- ence and technology, [16] especially in geology and mineralogy, [17–19] in environmental and biological research, [20] in mate- rial research for the characterization of high purity materials [21] and for the determination of long lived radio-nuclides in non- conducting materials [21,22]. 1387-3806/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ijms.2009.07.002