Chromatography of Mo(VI) and W(VI) chelates with 2,3-dihydroxynaphthalene

Mo(VI) and W(VI) were separated in the form of their anionic chelates with 2,3-dihydroxynaphthalene (DHN) by reversed phase ion-pair chromatography. The effect of the organic modifier content and concentration of tetrabutylammonium cations (TBA) in the mobile phase and the effect of concentration of DHN in the injected sample on the separation were studied. The best results were attained by using a mobile phase containing DHN (0.5 mmol dm-3), TBA counter-ions (10 mmol dm-3) and phosphate buffer (50 mmol dm-3) in a medium of 30% (v/v) methanol and 30% (v/v) acetonitrile at pH 7 and by injecting Mo(VI) and W(VI) samples containing DHN in a tenfold excess. On a CGC glass column 150 . 3.3 mm i.d. packed with Separon SGX C18 (5μm), the solutes were separated at resolutions of Rij = 1.0 (DHN-Mo) and 1.6 (Mo-W). The detection limits at 240 nm were 0.5 and 0.2 nmol for Mo(VI) and W(VI), respectively.