TECHNICAL NOTE Gold internal standard correction for elemental imaging of soft tissue sections by LA-ICP-MS: element distribution in eye microstructures Ioana Konz & Beatriz Fernández & M. Luisa Fernández & Rosario Pereiro & Héctor González & Lydia Álvarez & Miguel Coca-Prados & Alfredo Sanz-Medel Received: 13 November 2012 / Revised: 16 January 2013 / Accepted: 22 January 2013 / Published online: 5 February 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract Laser ablation coupled to inductively coupled plas- ma mass spectrometry has been developed for the elemental imaging of Mg, Fe and Cu distribution in histological tissue sections of fixed eyes, embedded in paraffin, from human donors (cadavers). This work presents the development of a novel internal standard correction methodology based on the deposition of a homogeneous thin gold film on the tissue surface and the use of the 197 Au + signal as internal standard. Sample preparation (tissue section thickness) and laser con- ditions were carefully optimized, and internal normalisation using 197 Au + was compared with 13 C + correction for imaging applications. 24 Mg + , 56 Fe + and 63 Cu + distributions were in- vestigated in histological sections of the anterior segment of the eye (including the iris, ciliary body, cornea and trabecular meshwork) and were shown to be heterogeneously distributed along those tissue structures. Reproducibility was assessed by imaging different human eye sections from the same donor and from ten different eyes from adult normal donors, which showed that similar spatial maps were obtained and therefore demonstrate the analytical potential of using 197 Au + as inter- nal standard. The proposed analytical approach could offer a robust tool with great practical interest for clinical studies, e.g. to investigate trace element distribution of metals and their alterations in ocular diseases. Keywords Laser ablation . Biological samples . Mass spectrometry/ICP-MS Introduction Bio-imaging analytical techniques with adequate spatial reso- lution are today of crucial interest in life science studies to achieve a deeper understanding of the role of metals in biolog- ical systems [1, 2]. In this vein, the use of laser ablation coupled to inductively coupled plasma mass spectrometry (LA-ICP- MS) has demonstrated a great potential for spatially resolved analysis of heteroatoms (especially metals) in different types of tissues, including mouse kidney and heart [3, 4], human lymph nodes and respiratory tissues [5, 6], liver biopsy, breast cancer or prostate tissues [7, 8] and brain sections [9, 10]. In general, such micro-local analysis is performed to study the accumula- tion of certain heteroatoms in the regions of interest as well as to compare the differences of the elements' distribution between non-pathogenic and pathogenic tissues. Both in qualitative and quantitative elemental imaging by LA-ICP-MS, different internal standards (IS) have been investigated to account for matrix effects as well as for variations in ablated mass, transported mass and instrumen- tal drift normally present in laser-based analysis techniques [11]. More conventional approaches in elemental bio- imaging applications employ the 13 C + signal for internal normalisation [5, 9, 10]. However, Frick et al. [12] have recently performed a detailed study of the ablation of carbon-containing matrices demonstrating the formation of two individual phases, a gaseous carbon-containing species and a carbon-containing particle phase. Such fundamental Electronic supplementary material The online version of this article (doi:10.1007/s00216-013-6778-4) contains supplementary material, which is available to authorized users. I. Konz : B. Fernández (*) : M. L. Fernández : R. Pereiro : A. Sanz-Medel (*) Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Julian Clavería 8, 33006 Oviedo, Spain e-mail: fernandezbeatriz@uniovi.es e-mail: asm@uniovi.es H. González : L. Álvarez : M. Coca-Prados Fundación de Investigación Oftalmológica, Instituto Oftalmológico Fernández-Vega, 33012 Oviedo, Spain Anal Bioanal Chem (2013) 405:3091–3096 DOI 10.1007/s00216-013-6778-4