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A. Limbeck, M. Weiss, Z. Gajarska, G. Ramer, B. Lendl, J. Lohninger:
"Analysis of fluorine in polymer samples using LIBS via measurement of molecular emission bands";
Vortrag: SCIX 2021, Providence, Rhode Island, USA; 26.09.2021 - 01.10.2021; in: "Full schedule", (2021), 1 S.

Synthetic polymers are widely used materials with a broad range of applications in all kinds of industries. At the end of their life-cycle, these high performance polymers often end up in the environment, either as packaging waste or in the form of micro-plastics, both of which pose a significant threat to various ecosystems. Since fluorine-containing polymers exhibit an extremely long lifetime in the environment, there is an increasing need for their qualitative and quantitative analysis.
However, compared to the elements chlorine, bromine and iodine, the measurement of fluorine is a rather difficult task. Moreover, the enhanced inertness of these polymers requires the use of sophisticated sample pretreatment procedures for sample dissolution, which hampers the application of inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography (IC) or ion-selective electrodes. One of the techniques showing a potential for the direct analysis of fluorine in polymers is laser induced breakdown spectroscopy (LIBS). However, sensitivity of fluorine analysis is limited as a result of the high excitation energy of this element. Recently, it has been shown that molecular LIBS allows to improve the detection sensitivity of such analysis. In this approach a molecular emission of the element of interest is detected instead of the atomic line itself [1]. For analytical purposes, either an element naturally occurring in the sample or an element intentionally added to the sample can be used as a partner for the formation of molecules. In the literature, several approaches of the latter are reported, including spiking of a powdered sample with an additive [2] or introduction of a nebulized liquid standard on the sample surface during the LIBS analysis [3].
As these approaches allow only bulk investigations, we would like to present a novel method for the introduction of the element acting as a molecule building partner for the fluorine detection, opening up the possibility of fluorine imaging in solid samples. Applicability of the proposed methodology is demonstrated for actual research tasks, in particular the quantitative measurement of fluorine in unknown polymer samples, and the mapping of the fluorine distribution in artificial polymer waste.

LIBS, Fluorine analysis, polymers, imaging