Abstract: A method for rapid determination of trace iron in high purity titanium by inductively coupled plasma mass spectrometry (ICP-MS) was developed. The high purity titanium samples are dissolved by hydrofluoric acid and nitric acid and directly determined by ICP-MS after being diluted to a fixed volume. The matrix effect is eliminated by a standard addition method, which avoids ion exchange, thermal hydrolysis precipitation or other complicated sample treatment methods. Taking methane (CH₄) as the reaction gas, the optimum working conditions of the dynamic reaction are optimized for the real sample. When the flow rate of CH₄ is 0.7 L/min, the R_pq is 0.55 and the R_pa is “0”, the interference of ArO⁺ (m/z=56) to ⁵⁶Fe⁺ is effectively eliminated. The standard addition curve of a high purity titanium sample is drawn under the determined testing conditions. The linear equation is y= 2745.53x+1708.19, and the correlation coefficient is 0.9999. The curve can be transformed into the calibration curve of “external standard method” and the linear equation is y=2745.53x+136.19. The iron content in other samples can be detected under this curve, no standard addition operation is needed in every sample, and the detection efficiency is not reduced. The detection limit and the quantification limit of method are 0.029 and 0.097 μg/g, respectively, the precision (RSD, n=11) is less than 7% , and the recovery is 97.5%~106.0%. The trace iron in three samples of the high purity titanium is determined, the results are 0.53, 0.96 and 4.74 μg/g, respectively. The determination process and results show that the method is suitable for rapid and accurate determination of trace iron in high purity titanium.

Key words: Inductively coupled plasma, High purity titanium, Iron, Standard addition, Dynamic reaction, Methane