Determination of Organic and Reduced Inorganic Sulfur by Multi-element Scanning Thermal Analysis

Abstract

Determination of organic sulfur in solid environmental samples has been difficult because there is no appropriate separation technology. Routine organic sulfur analysis has mostly been done indirectly by the difference between the total and the inorganic sulfur contents. This indirect analysis is tedious, accumulating multiple sampling and procedural errors, and has no chemical characterization information. There are modern technologies such as S-XANES for direct sulfur analysis on solid samples. But they are sophisticated, expensive, and unavailable for routine sulfur analysis. Due to those analytical difficulties, our understanding of sulfur chemistry in solid samples has been limited. This study was initiated to apply a convenient Multi-Element Scanning Thermal Analysis (MESTA) method for direct analysis of organic and reduced inorganic sulfur in solid samples. If successful, sulfur MESTA will be a convenient and powerful tool for studying environmental sulfur cycles and sulfur-containing materials. We used 27 reference organic and reduced inorganic sulfur compounds to validate the MESTA method. The results indicate that MESTA can directly quantify and characterize organic and reduced inorganic sulfur compounds. Recoveries of the reference compounds were in the range of 77.0% to 97.7% except for sulfate functional group containing compounds of bathophenanthrolinedisulfonic acid (57.4 ± 6.7%), sodium thiosulfate (60.6 ± 3.1%) and sodium dodecyl sulfate (38.0 ± 2.6%). MESTA is rapid, sensitive, and inexpensive. It is a convenient and powerful tool for sulfur analysis in a wide range of solid, liquid, or mixed samples.