A Practical and Selective Method for the Analysis of Molybdenum in Grade T91 Tube and P91 Pipe Intended for Power Plants
ASME SA-213 T91 tubes and SA-335 P91 pipes were widely used in combined-cycle steam systems due to their greater increased temperature strength and creep behavior. In this paper, a practical and selective spectrophotometric method for the determination of molybdenum in ASME SA-213 T91 tube and SA-335 P91 pipe samples has been presented. This method was based on the chromogenic reaction between molybdenum(V) and sodium thiocyanate. Employing stannous chloride as a reductant, molybdenum(VI) was reduced to molybdenum(V) at the room temperature. The obtained molybdenum(V) formed an orange-red-colored (1:5) ligand complex with thiocyanate. The absorbance of the complex was measured at 470nm, and the molar extinction coefficient is 1.75´104L·mol-1·cm-1. Under the optimum reaction conditions the absorption value was proportional to the concentration of molybdenum in the range of 0.40~1.21%, and the relative standard deviation was less than 3.0%. The proposed method was free from the interference from a large number of analytical important elements and has been applied satisfactorily to the determination of molybdenum in grade T91 tube and P91 pipe samples with the improved accuracy and precision.
Xiaoming Sang, Pengcheng Wang, Liqun Ai, Yungang Li and Jinglong Bu
Y. Li et al., "A Practical and Selective Method for the Analysis of Molybdenum in Grade T91 Tube and P91 Pipe Intended for Power Plants", Advanced Materials Research, Vols. 284-286, pp. 1510-1515, 2011