Mapping of macro and micro elements in the leaves of sunflower (Helianthus annuus) by Laser Ablation–ICP–MS

• Published in: Microchemical journal Vol. 110; pp. 783 - 789
• Main Authors: Kötschau, A., Büchel, G., Einax, J.W., Fischer, C., von Tümpling, W., Merten, D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2013
• Subjects: Element mapping; LA–ICP–MS; Leaves; Sunflower; Leaves; LA–ICP–MS; Element mapping; Sunflower
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1016/j.microc.2012.12.011

Distribution and behavior of contaminants in plants are of increasing interest both for food production and phytoremediation. Elements like Cd, Cr, Cu, Mn, Ni, and Zn are in the focus of investigations, due to their nutritive function, but also potential toxicity for plants and human. Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) was tested and a method developed to determine the spatial distribution and contents of macro and micro elements (Ca, Cd, Ce, Cr, Cu, Fe, K, La, Mn, Ni, P, S, and Zn) in leaves of sunflower (Helianthus annuus). The leaves were scanned in lines orthogonal to the leaf veins with a focused Nd:YAG-laser. The ion intensities of 13C+(internal standard), 31P+, 33S+, 39K+, 44Ca+, 52Cr+, 55Mn+, 56Fe+, 60Ni+, 63Cu+, 66Zn+, 111Cd+, 139La+, and 140Ce+ were measured with ICP-Quadrupole-MS. The standard reference material CTA-VTL-2 Virginia tobacco leaves was used for calibration. The precision and accuracy of the data were proven by determining the contents in standard reference materials IAEA-V-10 Hay, IAEA-359 Cabbage, NIST 1572 Citrus leaves, and NIST 1575 Pine needles. The robustness was tested by ablating CTA-VTL-2 while varying beam size, repetition rate, energy output, and transport gas flow rate according to a 24−1 fractional factorial design of experiments (DOE). The depth of the ablation craters was measured with Vertical Scanning Interferometry (VSI) and found to be about 30μm, regardless of the ablation of veins or mesophyll tissue of the leaf. With an in-house MATLAB® script quantitative imaging of the elemental distribution was possible. The different distribution patterns could be separated in four main groups: 1. Cd, Ce, Cu, La, Mn, and Zn accumulate at the veins of the leaves, 2. Fe and S accumulated with higher contents at the tip of the leaf, 3. K and Ni are enriched preferentially in the mesophyll, and 4. Ca, Cr, and P show homogeneous distributions over the whole leaf. ► Quantitative mapping of 13 macro and micro elements in leaves of sunflower Helianthus annuus with LA–ICP–MS. ► Distribution patterns give hints on binding and interaction of nutrients and toxic elements. ► Investigation of the laser ablation craters with Vertical Scanning Interferometry (VSI). ► Similar ablation behavior of mesophyll and leaf veins.