Technical note Detection efficiencies in nano- and femtosecond laser ablation inductively coupled plasma mass spectrometry M. Wälle a , J. Koch a, ⁎, L. Flamigni a , S. Heiroth b , T. Lippert b , W. Hartung c , D. Günther a, ⁎ a Laboratory of Inorganic Chemistry, ETH Zurich, Wolfgang-Pauli-Straße 10, CH-8093 Zurich, Switzerland b General Energy Research Department, Paul-Scherrer-Institut, CH-5232 Villigen-PSI, Switzerland c Laboratory of Surface Science and Technology, Department of Materials and Material Research Center, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland abstract article info Article history: Received 12 March 2008 Accepted 4 October 2008 Available online 1 November 2008 Keywords: Femtosecond laser ablation Nanosecond Inductively coupled plasma mass spectrometry Detection efficiency Detection efficiencies of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), defined as the ratio of ions reaching the detector and atoms released by LA were measured. For this purpose, LA of silicate glasses, zircon, and pure silicon was performed using nanosecond (ns) as well as femtosecond (fs) LA. For instance, ns-LA of silicate glass using helium as in-cell carrier gas resulted in detection efficiencies between approximately 1E-7 for low and 3E-5 for high mass range elements which were, in addition, almost independent on the laser wavelength and pulse duration chosen. In contrast, the application of argon as carrier gas was found to suppress the detection efficiencies systematically by a factor of up to 5 mainly due to a less efficient aerosol-to-ion conversion and ion transmission inside the ICP-MS. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Only a few years after the invention of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in the late 1980s, several studies about the aerosol transport efficiency were launched [1–3]. In 1988, Arrowsmith et al. [1] and, in 1993, Huang et al. [2] reported on transport efficiencies of up to 60%. Based on theoretical considerations involving diffusion and gravitation effects the authors, in addition, calculated a transportable particle size range varying from 0.005 μm to 2 μm [1] which, ever since, has been confirmed in, for instance, Refs. [4–6]. Recently, Garcia et al. [7] found transport efficiencies of approximately 80% achieved by femtosecond (fs) LA of metal targets. However, data presented did not account for particle deposition on the sample surface, which was assumed to be negligible for LA using helium as carrier gas. Nonetheless, deposition can be quite severe, in particular, if LA is carried out in argon atmosphere. Therefore, additional efforts were made and revealed that roughly 30% of the ablated mass deposits on the sample surface under conditions typically applied for analysis [8]. Examining the different sources of material losses, eventually, aims to optimize the LA protocol or cell design and, thus, to enhance accuracy and sensitivity of ICP-MS analyses. However, as suggested in [7] and [8], a significant increase of the transport efficiency cannot be expected, since values found for different cell designs, conventional ones as well as those assumed to be optimum, were almost equivalent at an already high level of 75%–95%. Consequently, the most promising strategies for increasing the sensitivity are, to shorten the wash-out time of the ablation cell and, thus, to increase the signal-to-noise-ratio [9] or to reduce ion losses inside the ICP-MS, i.e. improving the ion transmission. While the former approach can easily be accomplished using low-volume ablation cells as proposed in Refs. [1,7] or even in- torch LA, the latter one requires the utilization of sector field (SF) instruments, which are known to be the most sensitive instruments for MS-based analysis if operated in low resolution mode. 1 Alternatively, losses inside the ICP-MS interface and in front of the quadrupole filter must be minimized by increasing the over-all ion transmission which, however, would imply a redesign of currently available interfaces used in ICP-MS instruments. In order to assess the “hidden reserves” an improved ion throughput might offer, the de- tection efficiency (DE) defined as the ratio of ions reaching the detector and number of atoms released during LA needs to be known. According to the literature, there exist extensive data about DEs for solution nebulization (SN)-ICP-MS [10]. However, such values must not be understood as benchmark for LA as long as, e.g., aerosol losses Spectrochimica Acta Part B 64 (2009) 109–112 ⁎ Corresponding authors. Koch is to be contacted at Tel.: +41 44 632 4687; fax: +41 44 633 6151. Günther, Tel.: +41 44 632 4687; fax: +4144 633 1071. E-mail addresses: koch@inorg.chem.ethz.ch (J. Koch), guenther@inorg.chem.ethz.ch (D. Günther). 1 The ion transmission reported for SF-ICP-MS operated in low resolution mode is known to be roughly ten times higher than the one achieved by state-of-the-art Q-type instruments. 0584-8547/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.sab.2008.10.021 Contents lists available at ScienceDirect Spectrochimica Acta Part B journal homepage: www.elsevier.com/locate/sab