Sulfur fractionation using high-resolution continuum source molecular absorption spectrometry with calcium and...

The unprecedented use of high-resolution continuum source molecular absorption spectrometry (HR-CS MAS) for the fractionation of organic and inorganic sulfur (S) species through monitoring the CS molecule is presented here. Two separate methods for determining organic (CS_org) and inorganic (CS_ino) sulfur were developed to work sequentially. The optimized temperature program for both methodologies has two pyrolysis steps and one vaporization step (1st T_pyr: 1800 and 2^ndT_pyr: 800 °C, and T_vap: 2500 °C). The fractionation was achieved by implementing hydrophobic Pd NPs and Ca as chemical modifiers for the CS_org and CS_ino methods. Method development was performed by applying different statistical models, allowing the definition of optimal conditions for the chemical modifier mass, and minimizing the S species interconversion, i.e., Doehlert design, and central composite design. The limits of detection (LoD) for CS_org and CS_ino were 2.4 and 2.1 mg L^-1, respectively. Recovery tests evaluated the method's specificity and accuracy; over 92 % recovery was found for both CS_org and CS_ino. Thus, the proposed methods offer a reliable alternative for fractionating organic and inorganic S by using HR-CS MAS.