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+, 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 (AlOn+, 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 AlOn+ (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, AlOn+ (n = 0 to 3), which provide internal-cross-checkable quantitative results for this mono-isotopic element.

Determination of Rare Earth Elements by Inductively Coupled Plasma-Tandem Quadrupole Mass Spectrometry With Nitrous Oxide as the Reaction Gas.

Nitrous oxide (N2O) was investigated as the reaction gas for the determination of rare earth elements (REEs) by inductively coupled plasma-tandem quadrupole mass spectrometry (ICP-QMS/QMS). The use of N2O as the reaction gas apparently improved the yields of m M16O+ for Eu and Yb in the reaction cell. As a result, the sensitivities for measurement of Eu and Yb were apparently improved in comparison to those obtained with O2 as the reaction gas. A high sensitivity measurement of the whole set of REEs was achieved, providing a typical sensitivity of 300,000 CPS mL/ng for REEs measured with an isotope having isotopic abundance close to 100%. The use of N2O as the reaction gas helped suppress Ba-related spectral interferences with the measurement of Eu, permitting the measurement of Eu in a natural sample without mathematic correction of spectral interferences. The detection limits (unit, pg/mL) for 14 REEs (except for Pm) from La to Lu were 0.028, 0.018, 0.006, 0.026, 0.006, 0.010, 0.017, 0.006, 0.016, 0.010, 0.016, 0.004, 0.023, and 0.012, respectively. The validity of the present method was confirmed by determining REEs in river water-certified reference materials, namely, SLRS-3 and SLRS-4.

Quantification of Trace Arsenic in Whole Blood by ICP-QMS/QMS.

ICP-QMS/QMS was applied to whole blood samples to determine the quantity of trace As. It was found that Fe also causes polyatomic interference with As in conventional ICP-QMS, in addition to Ca and Cl, and ICP-QMS/QMS can remove these interferences in mass-shift mode using O2 as reaction gas. The ICP-QMS/QMS technique allows the determination of As at sub-ng mL-1 levels.

Determination of Rubidium by ID-ICP-QMS/QMS with Fluoromethane as the Reaction Cell Gas to Separate Spectral Interference from Strontium.

A determination of rubidium (Rb) was carried out by isotope dilution (ID) using an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-QMS/QMS) with an octupole reaction-cell (ORC). Spectral interference of 87Sr with the measurement of 87Rb was effectively removed by using fluoromethane (CH3F) as the reaction cell gas at the optimum flow rate. In comparison to the measurement obtained with a mathematical correction, good precision for the analysis of the Rb isotope could be obtained independent of the concentration of Sr without any chemical separation in advance. The usefulness of the present approach was confirmed by an analysis of Rb in multiple certified reference materials (CRMs) for food and environmental analysis, for which the results agreed with their certified values in the range of expanded uncertainty.

Analysis of Fluorine in Drinking Water by ICP-QMS/QMS with an Octupole Reaction Cell.

The analysis of fluorine was carried out by measuring BaF+ ions with an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-QMS/QMS). After optimization, a radio frequency power of 1300 W was found to benefit for the production of BaF+ ions while suppressing the production of BaOH3+ ions. After optimization of the reaction cell gas, it was found that the best performance for measuring BaF+ could be achieved at a flow rate of O2 in the range from 0.65 to 0.75 mL min-1. The signal intensity of BaF+ depended linearly on the concentration of Ba when it was not higher than 100 mg kg-1. The co-existence of metallic cations, such as Na in the sample, might suppress the generation of BaF+ ions in the plasma, while anions might not cause such a kind of interferences. The background equivalent concentration (BEC) and the lower detection limit (LDL) of fluorine were 0.4 and 0.06 mg kg-1, respectively, by adjusting the samples to a 10 mg kg-1 Ba matrix. The concentration of fluorine in a certified reference material (ERM-CA015a) was determined with the present method, for which the observed value was (1.36 ± 0.05)mg kg-1, which agreed with the certified value (1.3 ± 0.1)mg kg-1, where both values were shown as (mean value ± expanded uncertainty) with a coverage factor of (k = 2) for calculating the expanded uncertainty giving a level of confidence of approximately 95%. The present method was applied to the analysis of a tap water sample collected in the laboratory, for which the results of recovery tests gave a recovery around 100% with good reproducibility.

Experimental Confirmation of SrF(CH3F)0-4+ and SrF(H2O)(CH3F)0-3+ Cluster Ions Generated in the Reaction-cell of ICP-QMS/QMS.

Multiple unknown high-order cluster ions were observed as the results of ion-molecule reactions between strontium ions and fluoromethane molecules in the reaction-cell of an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-QMS/QMS). In order to elucidate the structures of these unknown cluster ions, isotope-enriched fluoromethane (CD3F) was used as the reaction-cell gas compared to natural fluoromethane (CH3F). As results, SrF(CH3F)0-4+ and SrF(H2O)(CH3F)0-3+ cluster ions were experimentally confirmed in the present work, while SrF(H2O)(CH3F)0-3+ cluster ions in the reaction-cell of ICP-QMS/QMS were observed and confirmed for the first time in the world.