Quantitative Imaging of Selenium, Copper, and Zinc in Thin Sections of Biological Tissues (Slugs−Genus Arion) Measured by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Abstract

Quantitative imaging analysis of endogenous an exogenous elements throughout entire organisms is required for studies of bioavailability, transport processes, distribution, contamination and to monitor environmental risks using indicator organisms. An imaging mass spectrometric technique using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) was developed to analyze selenium and metal distributions in longitudinal sections (thickness, 100 microm) of entire slugs (genus arion). Slugs were fed with either a placebo or solutions containing 1000 microg mL(-1) Se. Samples (raster area, 25 mmx45 mm) were scanned together with synthetic matrix-matched standards with a focused beam of a Nd:YAG laser (wavelength, 266 nm; diameter of laser crater, 50 microm; laser power density, 3x10(9) W cm(-2)) in a large laser ablation chamber. The ablated material was transported with argon as carrier gas to the ICP ion source at a double focusing sector field ICPMS. Ion intensities of selenium (78Se+, 82Se+) were measured together with 13C+, 63Cu+, and 64Zn+ within the entire tissue section. The regression coefficient of the calibration curve was 0.998. Inhomogeneous distributions for Se but also for C, Cu, and Zn were found. Selenium was enriched in the kidney (150 microg g(-1) in Se-treated animals versus 15 microg g(-1) in the placebo-treated animal, respectively) and in the digestive gland (200 microg g(-1) versus 25 microg g(-1)). Highest Se concentrations were detected in the gut of Se-treated slugs (250 microg g(-1)), and additional Se occurred in the skin of these animals. Cu was enriched in the heart and the mucous ventral skin. Interestingly, in addition to the localization in the digestive gland, Zn was detected only in the dorsal skin but not the ventral skin. The developed analytical technique allows the quantitative imaging of selenium together with selected metals in thin sections of biological tissue with limits of detection at the submicrogram per gram range.