Determination of Zr, Nb, Mo, Sn, Hf, Ta, and W in seawater by N-benzoyl-N-phenylhydroxylamine extraction chromatographic resin and inductively coupled plasma-mass spectrometry

• A novel BPHA extraction chromatographic preconcentration has been evaluated.
• This method analyzed trace levels of Zr, Hf, Nb, Ta, W, Sn and Mo in seawater.
• 0.5 mL of the resin is enough to separate Zr, Nb, Mo, Sn, Hf, Ta and W from matrix.
• The procedure yields > 95% recovery and has extremely low total method blank.
• The procedure has proved to be practical and effective for seawater analysis.

A method has been developed for the determination of zirconium (Zr), hafnium (Hf), niobium (Nb), tantalum (Ta), molybdenum (Mo), tungsten (W), and tin (Sn) in seawater by quadrupole inductively coupled plasma-mass spectrometry (Q-ICP-MS). The method is based on separation of the seven elements by extraction chromatography using N-benzoyl-N-phenylhydroxylamine (BPHA) supported on a microporous acrylic ester polymeric resin. The optimized procedure indicates that the BPHA resin has high selective adsorption for Zr, Nb, Mo, Sn, Hf, Ta, and W (known as fluoride soluble elements), whereas other interference and matrix elements are minimally adsorbed. The optimized eluent mixture with their molarity gives satisfactory recoveries for all analytes. The recovery can be achieved 99% for Zr, 97% for Nb, 97% for Mo, 99% for Sn, 99% for Hf, 95% for Ta, and 98% for W, respectively, by eluting with 6 mL of 6 mol L− 1 HF/1 mol L− 1 HCl. Furthermore, the technique for separation and enrichment of these elements provides a low total method blank. The detection limits for this method are 0.5 ppt for Zr, 0.2 ppt for Nb, 1.7 ppt for Mo, 1.0 ppt for Sn, 0.1 ppt for Hf, 0.1 ppt for Ta, and 0.3 ppt for W, respectively. The validity of the method is evaluated by replicate analyses of seawater reference materials; the precision of the results is better than 3% (RSD, n = 4), and the results are in good agreement with certified values. The established procedure has proved to be both practical and effective for seawater sample analyses.