Determination of chlorine in cement via CaCl molecule by high-resolution continuum source graphite furnace molecular absorption spectrometry with direct solid sample analysis

The use of a new molecule the calcium mono-chloride (CaCl) with absorption band head at 621.145 nm was evaluated in the development of a method for Cl determination in cement by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GFMAS) employing direct solid sample analysis. Calcium compounds present in cement samples acted as CaCl-forming reagent. Pyrolysis and vaporization curves were established to optimize the atomizer temperature program. The optimum pyrolysis and vaporization temperatures were 1000 °C and 2200 °C, respectively. These values provided higher thermal stability of the CaCl molecule which allows reducing matrix effects and the calibration with aqueous standard solutions in the range of 10-200 ng Cl. Correlation coefficient of 0.995 and a slope of 0.00159 s ng− 1 were obtained, with a calculated limit of detection of 1.4 ng Cl. Sample masses in the range 0.65-1.05 mg can be accurately weighed and assayed. Commercial cement samples were analyzed by the proposed method and the concentrations of Cl were in the 159-540 μg g− 1 concentration range. Samples were also analyzed by the Brazilian Association of Technical Norms (ABNT) and results were in agreement at a 95% confidence level (paired t-test). Recoveries of Cl added to samples were in the range 101-118% and the relative standard deviations (n = 12) were in the 3.4-11.2% interval.