I'm basing my project around Alizarin Red S as the reagent of choice to test Cd in water lakes as my samples. I'm on the verge of ordering it from Sigma-Aldrich (Product No. A5533). Although it seems to be the same, it still had a different IUPAC name (Sodium 9,10-dihydro-3,4-dihydroxy-9,10-dioxoanthracene-2-sulphonate monohydrate) whereas the one i read in a few papers had mentioned (1, 2-dihydroxyanthraquinone-3-sulphonic acid,). I was hoping if anyone could tell me whether the 2 are the same essentially or not.