title: Elimination of oxide interferences and determination of ultra-trace silver in soils by ICP-MS with ion-molecule reactions.
abstract: Silver is subject to significant spectral interferences caused by high concentrations of Zr, Nb, Mo and Y in inductively coupled plasma mass spectrometry (ICP-MS) analysis for soil or sediment samples. In this study, the Zr, Nb, and Mo based oxide and/or hydroxide polyatomic interferences were successfully eliminated by ion-molecule reactions in a dynamic reaction cell (DRC). These potentially interfering ions ⁹³Nb¹⁶O+, ⁹²Zr¹⁶OH+ and ⁹²Mo¹⁶OH+ on ¹⁰⁹Ag+ were rapidly oxidized to higher oxides ⁹³NbO₂+, ⁹²ZrO₂H+/⁹²ZrO₂H+ and ⁹²MoO₂H+ by O₂ as the reaction gas in DRC. However, interfering ions ⁸⁹Y¹⁸O+ and ⁹¹Zr¹⁶O+ on ¹⁰⁷Ag cannot be removed by this method, because the reaction rates of ZrO+ and YO+ to ZrO₂+/ZrO₃+ and YO₂+/YO₃+ were too low. Under the optimized O₂ flow rate (2.4 mL min⁻¹) and DRC rejection parameter q (Rpq, 0.75), the background signal was reduced by up to 100-fold at m/z 109 and the limit of quantitation (LOQ, 10σ) for ¹⁰⁹Ag was 0.5 ng g⁻¹. The proposed method was used to determine the concentration of Ag in twenty-eight soil standard reference materials (SRMs). The accuracy of the results suggests that the method has great potential for the direct determination of trace or ultra-trace levels of Ag in various environmental samples.
authors.affiliation: Key Laboratory of Biogeology and Environmental Geology of Ministry of Education, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, PR China. guowei012345@163.com
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
authors.forename: Shenghong
authors.initials: S
authors.lastname: Hu
authors.forename: Jiangyi
authors.initials: J
authors.lastname: Zhang
authors.forename: Hongfei
authors.initials: H
authors.lastname: Zhang
mesh_terms: D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D010087:Oxides / Q000737:chemistry; D012834:Silver / Q000032:analysis* / Q000737:chemistry; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry; D013054:Spectrophotometry, Atomic; D014131:Trace Elements / Q000032:analysis / Q000737:chemistry
chemical_list: D010087:Oxides; D012987:Soil; D012989:Soil Pollutants; D014131:Trace Elements; D012834:Silver