SLIDING SPARK SPECTROSCOPY - CHARACTERIZATION AND APPLICATION OF A NEW RADIATION SOURCE IN OPTICAL-EMISSION SPECTROMETRY FOR THE IDENTIFICATION OF CHLORINE-CONTAINING WASTE PLASTICS AND THEIR INORGANIC ADDITIVES

A new analytical radiation source combined with fiber optics linked to a diode array detection device with modified software is described. T he direct-reading spectrometer simultaneously covers the wavelength ra nge 185-510 nm with a spectral resolution of <1.5 nm. Intense optical emission is observed when positionally stable high-current surface spa rks supplied by a pulse-generator with definite discharge parameters ( max. 800 Ampere/pulse) are sliding over compact non-conductive materia ls such as plastics, glasses, quartz filters or powder pellets. Substr ate vaporization, ionization and excitation processes in the surface d ischarge plasma channel generate emission corresponding to neutral and ionic states. The spectra are essentially composed of lines emitted b y the electrode material (e. g. copper, silver), from the substrate un der investigation, radiation continuum as well as structured backgroun d from the surrounding air atmosphere. Due to the occurrence of emissi on lines of reactive fillers, inorganic pigments and stabilizers, a ra pid multi-element screening method is demonstrated. A rapid identifica tion system (mix-up test) of PVC or fire-retardant thermoplastics with in one second has been realized from the atomic emission line intensit y originating from the sputtered copper electrode material according t o its increased volatility in the presence of chlorine (modified Beils tein test).