Ozone reaction induced multiple ionic species for internal-cross-checkable determination of aluminium by tandem quadrupole inductively coupled plasma mass spectrometry.

BACKGROUND

Aluminium is a mono-isotope element and can be determined by inductively coupled plasma mass spectrometry (ICP-MS). The measurement of aluminium by ICP-MS suffers potential spectral interferences from multiple elements, which make it challenging to ensure the reliability of the results. Fortunately, the availability of tandem quadrupole ICP-MS (i.e. ICP-QMS/QMS) made it possible to measure multiple aluminium related ionic species for analysis. In the present work, on-line generated ozone was introduced as the reaction gas to the ICP-QMS/QMS for the analysis of aluminium.

RESULTS

Multiple ionic species were obtained by using ozone as the cell gas for determination of aluminium by ICP-QMS/QMS. In comparison to oxygen, ozone apparently improved the yield of AlO, AlO, and AlO from the reaction with Al, attributable to the exothermic reactions when ozone was used. Determination of aluminium with these product ions was investigated at multiple radio frequency (RF) power conditions (800 W-1600 W, step 200 W) for the plasma. At low power conditions (800 W and 1000 W), the measurement of each ion suffered notable non-spectral interferences and caused difference in sensitivities by around 20 % between a digested sample of tea leaf powder and a simple aluminium standard solution. Based on a standard addition method, the result of aluminium in a tea leaf powder certified reference material obtained with each product ion (AlO, n = 0 to 3) agreed with the certified value, and independent to the RF power of the plasma.

SIGNIFICANCE

Due to the endothermic reactions of aluminium ion with ozone, the yields of AlO (n = 1 to 3) were greatly improved. As a results, the use of ozone as a reaction gas for ICP-QMS/QMS permitted the measurement of aluminium by multiple ionic species, AlO (n = 0 to 3), which provide internal-cross-checkable quantitative results for this mono-isotopic element.