Ozone reaction induced multiple ionic species for internal-cross-checkable determination of aluminium by tandem...

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.

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⁺, AlO₂⁺, and AlO₃⁺ 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⁺, n = 0 to 3) agreed with the certified value, and independent to the RF power of the plasma.

Due to the endothermic reactions of aluminium ion with ozone, the yields of AlO_n⁺ (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⁺ (n = 0 to 3), which provide internal-cross-checkable quantitative results for this mono-isotopic element.