ChemicalName: 3,3'-Bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolsulfonphthalein, disodium salt CAS: 1611-35-4
Appearance: Reddish orange or reddish purple powder
Absorbance (0.014 mmol/l): ≥0.210 (around 440 nm)
Sensitivity: To pass test
MW: 716.62, C31H30N2Na2O13S
Storage Condition: ambient temperature, protect from metal
Shipping Condition: ambient temperature
XO is a colorimetric reagent and metal indicator of various metal ions. It is readily soluble in water. Its proton dissociation constants are reported to be -1.74, -1.09, 0.76, 1.15, 2.58, 3.23, 6.40, 10.5, and 12.6 (ion strength: 0.2). The color of the aqueous XO solution is yellow at pH < 6.3 and pink at pH > 6.5, and turns reddish-violet in the presence of metal ions. XO forms complexes with various metal ions in acidic conditions. Therefore, XO can be used to determine Ca, Cd, Mg, Pb, and Zn in the presence of Zephiramine in acidic conditions. XO is also a very versatile indicator for EDTA titration in acidic solutions.
1. D. C. Olson, et al., Semixylenol Orange: A Sensitive Reagent for Zirconium. Anal Chem. 1962;34:1299-1302.
2. M. Murakami, et al., Separation and Acid Equilibria of Xylenol Orange and Semi-xylenol Orange. Talanta. 1967;14:1293-1307.
3. Z. Nan, et al., Spectrophotometric Determination of Bismuth with Semi-xylenol Orange and Its Application in Metal Analysis. Talanta. 1989;36:733-737.
Table 1 Colorimetric Determination of Metal Ions Using XO