Determination of Pu isotopes in eawater by an on-line sequential injection technique with sector field inductively coupled plasma mass spectrometry

An on-line sequential injection (SI) system combined with sector field inductively coupled plasma mass spectrometry was developed for the determination of ultratrace level Pu-239 and Pu-240 in seawater. The potential of this method is the substantial reduction of a sample volume and rapidity in the determination of Pu isotopes. A chemical purification and preconcentration of Pu isotopes were accomplished by the on-line S1 system with two micro-columns of solid-phase extraction resins, Sr-Spec and TEVA-Spec. The MCN-6000 microconcentric nebulizer was used as a sample introduction system because of low interference effect and good sample utilization. With this method, it was possible to analyze ultratrace levels of Pu isotopes in only 5 L of surface seawater with an analysis speed of 4 h/sample. The precision of the measurement for the Pu-239 and Pu-240 was less than 3.4 (n = 7) and 5% (n = 7) for 5 L of seawater. The detection limits for Pu-239 and Pu-240 were 0.64 (1.5 muBq/mL) and 0.19 fg/mL (1.6 muBq/mL), respectively. The accuracy of this method was verified by using the reference seawater (IAEA-381) as well as by the comparison with the alpha-spectrometry.