Determination of trace molybdenum by solid substrate-room temperature phosphorescence quenching method based on catalytic effect of H2O2 on formation of ion association complex [Rhod.B]+·B[(C6H6)4]− Original Research Article

A new solid substrate-room temperature phosphorescence (SS-RTP) quenching method for the determination of trace molybdenum has been established. The SS-RTP can be quenched by H2O2 oxidizing [Rhod.B]+·B[(C6H6)4]− ion association complex, which is formed of Rhod.B reacting with NaB(C6H6)4 and [Rhod.B]+·B[(C6H6)4]− ion association complex can emit strong and stable room temperature phosphorescence on filter paper substrate, while molybdenum can catalyze H2O2 to oxidize [Rhod.B]+·B[(C6H6)4]− ion association complex to quench the SS-RTP sharply in HCl medium, heated at 90 °C for 10 min. Based on the facts above, a new method for the determination of trace molybdenum has been proposed. When using PVA–H3BO3–NaOH to modify the surface of filter, the results showed that ΔIp of the system enhanced 1.5 times than that of unmodified. The linear range of this method is 1.6–160 ag spot−1 (the sample volume: 0.40 μl spot−1), and the regression equation of working curve is ΔIp = 18.23 + 0.8935mMo(VI) ag spot−1, n = 6, r = 0.9980. The detection limit is 0.34 ag spot−1 (corresponding concentration: 8.5 × 10−16 g ml−1). This method has been successfully applied to the determination of trace molybdenum in actual samples with special feature such as wide linear range, high sensitivity, good repeatability, high selectivity and so on. Meanwhile, the mechanism of catalysis reaction is also discussed.