Determination of trace concentrations of chlorine in aqueous solutions by high-resolution continuum source graphite furnace molecular absorption spectrometry

Trace concentrations of total chlorine were determined by means of molecular absorption of indium mono-chloride (InCl) at 267.217nm using high-resolution continuum source graphite furnace molecular absorption spectrometry. The effects of chemical modifiers and the amount of In on the sensitivity and accuracy were investigated. The optimum pyrolysis and vaporization temperatures were 600°C and 1400°C, respectively. The limit of detection and characteristic mass were found to be 0.10ng and 0.21ng, respectively. Potential non-spectral and spectral interferences were tested for various metals and non-metals at concentrations up to 50mgL−1 and for phosphoric, sulphuric and nitric acids. No spectral interferences were observed. Significant non-spectral interferences were observed with F, Br, and I at concentrations higher than 1mgL−1, 5mgL−1 and 25mgL−1, respectively, which is probably caused by formation of competitive indium halogen molecules. Higher concentrations of mineral acids depressed the signal owing to the formation of volatile HCl. The calibration curve was linear in the range between 0.3 and 10ng with a correlation coefficient of R=0.993. The elaborated method was used for the chlorine determination in various waters and a drug sample. [Display omitted] •A new method for chlorine determination via the InCl molecule was developed.•The InCl molecule was measured using the spectral line at 267.217nm.•A method is linear up to 10ng of chlorine.•The LOD and characteristic mass for the method are 0.10ng and 0.21ng, respectively.•The determination of chlorine is possible in both inorganic and organic compounds.