title: Detection of arsenic(III) through pulsed laser-induced desorption/ionization of gold nanoparticles on cellulose membranes.
abstract: We have developed an assay based on gold nanoparticle-modified mixed cellulose ester membrane (Au NPs-MCEM) coupled with laser-induced desorption/ionization mass spectrometry (LDI-MS)-for the detection of arsenic(III) ions (arsenite, AsO2(-)) in aqueous solution. When the Au NPs reacted with lead ions (Pb(2+)) in alkaline solution (5 mM glycine-NaOH, pH 12), Au-Pb complexes, PbO, and Pb(OH) were formed immediately on the Au NP surfaces. The Pb species reacted rapidly with subsequently added AsO2(-) to form PbOAs2O3, (PbO)2As2O3, and/or (PbO)3As2O3 shells (2-5 nm) on the Au NPs' surfaces. As a result, significant observable aggregation of the Au NPs occurred in the solution. This Pb(2+)/Au NP probe allowed the detection of AsO2(-) at concentrations as low as 0.6 μM with high selectivity (at least 100-fold over other anions and metal ions). To further improve the sensitivity, we prepared Au NPs-MCEM for the LDI-MS-based detection of AsO2(-) ions. The intensity of the signal for the [Pb](+) ions in the mass spectra increased when the Au NPs-MCEM reacted with AsO2(-); in contrast, the intensity of the signal for [Au](+) ions decreased. Accordingly, the [Pb](+)/[Au](+) peak ratio increased upon increasing the AsO2(-) concentration over the range from 10 nM to 10 μM. The limit of detection at a signal-to-noise ratio of 3 was 2.5 nM, far below the action level of As (133 nM, ca. 10 ppb) permitted by the US EPA for drinking water. Relative to other nanoparticle-based arsenic sensors, this approach is rapid, specific, and sensitive; in addition, it can be applied to the detection of AsO2(-) in natural water samples (in this case, streamwater, lake water, tap water, groundwater, and mineral water).
authors.affiliation: Institute of Bioscience and Biotechnology, National Taiwan Ocean University , Keelung, 20224, Taiwan.
authors.forename: Cheng-I
authors.initials: CI
authors.lastname: Weng
authors.forename: Jin-Shun
authors.initials: JS
authors.lastname: Cang
authors.forename: Jia-Yaw
authors.initials: JY
authors.lastname: Chang
authors.forename: Tung-Ming
authors.initials: TM
authors.lastname: Hsiung
authors.forename: Binesh
authors.initials: B
authors.lastname: Unnikrishnan
authors.forename: Yu-Lun
authors.initials: YL
authors.lastname: Hung
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Tseng
authors.forename: Yu-Jia
authors.initials: YJ
authors.lastname: Li
authors.forename: Yu-Wei
authors.initials: YW
authors.lastname: Shen
authors.forename: Chih-Ching
authors.initials: CC
authors.lastname: Huang
mesh_terms: D001151:Arsenic / Q000032:analysis*; D002482:Cellulose / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D008567:Membranes, Artificial; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles
chemical_list: D008567:Membranes, Artificial; D006046:Gold; D002482:Cellulose; D001151:Arsenic