Determination of boron using mannitol-assisted electrothermal vaporization for sample introduction in inductively coupled plasma mass spectrometry

Abstract

The possibility of improving the detection sensitivity for boron with the use of mannitol as a chemical modifier in electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) is presented. Experiments were performed by adding mannitol to a boron analyte solution to form a boron–mannitol complex and then injecting the resulting product into the ETV-ICP-MS system for determination. The effect of mannitol on the signal pulse of boron was investigated by monitoring the analyte through a heating cycle from 150 to 2600 °C. The appearance of several marked signal pulses at temperatures between 425 and 1500 °C was observed and assumed to result from the vaporization of boron–mannitol complexes. The signal intensity of boron in the presence of mannitol was found to be considerably enhanced in comparison with that in its absence. The optimization of the ETV and ICP parameters and the amount of mannitol added and the comparison of mannitol with different modifier systems were subsequently investigated. It was found that by following the established method the sensitivity for boron in the presence of mannitol can be improved by a factor of 84 compared with that without the modifier, and the limits of detection (3 s) achieved in the presence of mannitol can be as low as 0.2 ng ml^–1 with a 20 µl injection. The large boron sensitivity enhancement in the presence of mannitol in ETV-ICP-MS is attributed to the formation of a boron–mannitol complex that is subsequently vaporized from the graphite surface and transported with the assistance of mannitol to the plasma. A novel application with mannitol, which acts both as a preconcentrating agent for boron in the chemical separation process and as a modifier in the ETV-ICP-MS for the determination of boron in trichlorosilane, is also presented.