Chemical speciation of chlorine in atmospheric aerosol samples by high-resolution proton induced X-ray emission spectroscopy

► Chemical specation of Cl in aerosol samples by high resolution PIXE spectroscopy. ► Fine structure of Kα and Kβ lines of reference compounds and APM samples was given. ► Kα spectra were well aligned with each other confirming the same Cl oxidation state. ► Pronounced chemical effects were observed in the Kβ spectra. ► We showed that chemical speciation of Cl was possible on thin aerosol samples.