Determination of chlorine in food samples via the AlCl molecule using high-resolution continuum source molecular absorption spectrometry in a graphite furnace

Determination of chlorine using the molecular absorption of aluminum mono-chloride (AlCl) at the 261.418 nm wavelength was accomplished by high-resolution continuum source molecular absorption spectrometry using a transversely heated graphite tube furnace with an integrated platform. For the analysis, 10 μL of the sample followed by 10 μL of a solution containing Al–Ag–Sr modifier, (1 g L− 1 each), were directly injected onto the platform. A spectral interference due to the use of Al–Ag–Sr as mixed modifier was easily corrected by the least-squares algorithm present in the spectrometer software. The pyrolysis and vaporization temperatures were 500 °C and 2200 °C, respectively. To evaluate the feasibility of a simple procedure for the determination of chlorine in food samples present in our daily lives, two different digestion methods were applied, namely (A) an acid digestion method using HNO3 only at room temperature, and (B) a digestion method with Ag, HNO3 and H2O2, where chlorine is precipitated as a low-solubility salt (AgCl), which is then dissolved with ammonia solution. The experimental results obtained with method B were in good agreement with the certified values and demonstrated that the proposed method is more accurate than method A. This is because the formation of silver chloride prevented analyte losses by volatilization. The limit of detection (LOD, 3σ/s) for Cl in methods A and B was 18 μg g− 1 and 9 μg g− 1, respectively, 1.7 and 3.3 times lower compared to published work using inductively coupled plasma optical emission spectrometry, and absolute LODs were 2.4 and 1.2 ng, respectively.