Detection of tire tread particles using laser-induced breakdown spectroscopy ☆ David Prochazka a,d, ⁎, Martin Bilík b , Petra Prochazková c , Jakub Klus d , Pavel Pořízka d , Jan Novotný d , Karel Novotný c,d , Barbora Ticová c , Albert Bradáč b , Marek Semela b , Jozef Kaiser a,d a Brno University of Technology, Institute of Physical Engineering, Technická 2, 616 00 Brno, Czech Republic b Brno University of Technology, Institute of Forensic Engineering, Údolní 244/53, 602 00 Brno, Czech Republic c Masaryk University, Faculty of Science, Department of Chemistry, Kamenice 735/5, 625 00 Brno, Czech Republic d Brno University of Technology, Central European Institute of Technology, Technická 3058/10, CZ-616 00 Brno, Czech Republic abstract article info Article history: Received 26 June 2014 Accepted 12 March 2015 Available online 25 March 2015 Keywords: LIBS Tire tread Optimization The objective of this paper is a study of the potential of laser induced breakdown spectroscopy (LIBS) for detec- tion of tire tread particles. Tire tread particles may represent pollutants; simultaneously, it is potentially possible to exploit detection of tire tread particles for identification of optically imperceptible braking tracks at locations of road accidents. The paper describes the general composition of tire treads and selection of an element suitable for detection using the LIBS method. Subsequently, the applicable spectral line is selected considering interferences with lines of elements that might be present together with the detected particles, and optimization of measure- ment parameters such as incident laser energy, gate delay and gate width is performed. In order to eliminate the matrix effect, measurements were performed using 4 types of tires manufactured by 3 different producers. An adhesive tape was used as a sample carrier. The most suitable adhesive tape was selected from 5 commonly avail- able tapes, on the basis of their respective LIBS spectra. Calibration standards, i.e. an adhesive tape with different area content of tire tread particles, were prepared for the selected tire. A calibration line was created on the basis of the aforementioned calibration standards. The linear section of this line was used for determination of the de- tection limit value applicable to the selected tire. Considering the insignificant influence of matrix of various types of tires, it is possible to make a simple recalculation of the detection limit value on the basis of zinc content in a specific tire. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The ability to detect tire tread particles in real time and in-situ has importance to a number of real world applications. Wide attention was recently dedicated to a tire tread particles as a source of pollution in environment. It was shown that tire treads contain heavy metals such as Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb [1]. Concurrently with the in- crease of road traffic, the level of environmental pollution increases not only due to exhaust from combustion engines but also in connection with tire tread particles. Tire tread particles are released mainly in con- nection with vehicle speed changes; to a lesser extent, however, they are released even in the course of continuous driving. The respective particles consequently pollute air, soil and, subsequently, water sources [1–4]. Another possibility of exploitation of fast detection of tire tread par- ticles might pertain to detection of optically imperceptible braking tracks. This thesis is based on the prerequisite that intense braking re- sults in a higher level of abrasion of a tire tread than in the case of stan- dard driving; therefore the average concentration of tire tread particles on a road surface would be statistically higher at places where braking was performed — in comparison with places where braking was not performed. Introduction of modern braking assistance systems (Anti- lock Braking System, Electronic Stability Control) results in low levels of tire sliding during braking, and therefore braking tracks prove to be visually very badly identifiable. This fact significantly impedes analyses of accidents so it is essential to seek methods and procedures of identi- fication of even such braking tracks. At present there are two different approaches to detection of tire tread particles. One of them is their detection on the basis of identification of polymers. For example, Gueissaz and Massonnet used pyrolysis in combi- nation with gas chromatography and mass spectrometry (Py-GC/MS) [5] for detection of tire tread particles. Another example of a method used for detection of tire tread particles on the basis of typical polymers is, for ex- ample, infrared spectrometry (IR) [6]. Spectrochimica Acta Part B 108 (2015) 1–7 ☆ Selected paper from the European Symposium on Atomic Spectrometry ESAS 2014 & 15th Czech-Slovak Spectroscopic Conference, Prague, Czech Republic, 16–21 March 2014. ⁎ Corresponding author at: Brno University of Technology, Institute of Physical Engineering, Technická 2, 616 00 Brno, Czech Republic. Tel.: +420 5 4114 2828. E-mail address: prochazka.d@fme.vutbr.cz (D. Prochazka). http://dx.doi.org/10.1016/j.sab.2015.03.011 0584-8547/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Spectrochimica Acta Part B journal homepage: www.elsevier.com/locate/sab