GB/T 4325.7-2013 standard specifies methods for the determination of iron in molybdenum, including o-phenanthrene Spectrophotometric method, spec-trophotometry and Inductance coupled plasma emission Light spectrum method. The standard applies to the determination of iron in molybdenum powder, molybdenum bar, molybdenum trioxide and ammonium molybdate. The measurement range of o-phenanthrene Spectrophotometric method, spec-trophotometry is 0.0005% to 0.060%, and the measurement range of Inductance coupled plasma emission Light spectrum method is 0.0002% to 0.100%. The standard describes in detail the sample handling, reagent requirements and instrument conditions to ensure the accuracy of the measurement results. For reagents and instruments required for analysis, the standard specifies the use of confirmed analytically pure reagents and instruments that comply with specific technical parameters to ensure Reliability and accuracy of analysis.