Optimization of methodology for the simultaneous speciation of inorganic As, Sb and Se in fluid samples by sector-field ICP-MS coupled to HPLC
|Other Titles:||Optimierung der Methode für die gleichzeitige Speziation von anorganischen As, Sb und Se in Flüssigkeitsproben durch Sektorfeld-ICP-MS HPLC gekoppelten||Authors:||Wu, Debo||Supervisor:||Pichler, Thomas||1. Expert:||Pichler, Thomas||2. Expert:||Koschinsky, Andrea||Abstract:||
Metal speciation provides information useful in the study of toxicity, bioavailability, adsorption, and redox behavior of element species. Based on inductively coupled plasma mass spectrometry (ICP-MS) coupled to high performance liquid chromatography (HPLC), in this project, a systematic investigation was made regarding chromatographic methods for the simultaneous speciation of arsenic (As), antimony (Sb) and selenium (Se) redox couples, and preservation strategies of these species. Finally, the developed method was applied to the analysis of hydrothermal water samples, with the purpose of studying As and Sb inorganic species distribution in hydrothermal systems. In the first study, a new method was developed for the simultaneous speciation analysis of inorganic As(III, V), Sb (III, V) and Se(IV, VI) in fluid samples by sector field-ICP-MS coupled with HPLC. Hamilton PRX-X100 anion-exchange column with EDTA (pH of 4.7) and 3% methanol as mobile phase was used for the separation of these species. The overall analysis time was within 11minutes for all six desired species. A thorough validation concerning stability of retention time, linearity and spike recovery was carried out. Low detection limits of these species, 0.02 Ã ¼g L-1 for As(III), 0.06 Ã ¼g L-1 for As(V), 0.2 Ã ¼g L-1 for Sb(III), 0.02 Ã ¼g L-1 for Sb(V), 0.2 Ã ¼g L-1 for Se(VI) and 0.4 Ã ¼g L-1 for Se(IV), make it possible for simultaneous study of competitive adsorption, redox behavior of these species. In the second study, preservation method and stability of As, Sb and Se redox couples were investigated in Fe- and Mn- rich water samples (groundwater, river water and lake water). As potential preservation strategies EDTA alone and EDTA combined with either HCl, HNO3, formic acid or acetic acid were studied and compared to unpreserved samples. The results showed that addition of EDTA combined with acidification to a pH of 3 successfully preserved all three redox couples for at least 11 weeks stored at 4 Ã¯ °C in the dark. EDTA alone (pH = 6) failed to preserve As and Sb species, especially for Sb(III) which was eventually completely oxidized in all samples. On the other hand, in the unpreserved samples, As, Sb and Se redox species showed different adsorption behaviors. As(III), Sb(III), Se(IV)) and As(V) were strongly adsorbed by Fe-(oxy)hydroxide and possibly Mn-(oxy)hydroxide. While Sb(V) and Se(VI) were not adsorbed in most cases. In the third study, the developed speciation method was used for the analysis of hydrothermal waters from Bali and Java, Indonesia. The results showed that the distribution of As and Sb species were closely correlated to Cl-, HCO3- and SO42-. Generally, in HCO3-type hydrothermal waters As(V) seemed the dominant species. In Cl-type samples, it is more complicated. Since extremely high concentration of Cl might be originated from either magma degassing (HCl gas) or seawater feeding, thus other oxidation processes may be involved in As species distribution. Our primary speciation results indicated that when the hydrothermal waters were affected by seawater feeding, As(V) was the main existing form, probably due to microbial activity. In SO4-type hydrothermal waters, As distribution is variable, either As(III) or As(V) could be the dominant species. In addition, an unknown As species was detected in 5 of the 18 samples, particularly in 2 samples this unknown species was even the main existing form for As, indicating that microbial activity was involved. For Sb species, Sb(V) was generally the main species in the analyzed samples.
|Keywords:||simultaneous speciation, ICP-MS, HPLC, preservation, application, arsenic, antimony and selenium||Issue Date:||10-Jun-2015||URN:||urn:nbn:de:gbv:46-00104616-14||Institution:||Universität Bremen||Faculty:||FB5 Geowissenschaften|
|Appears in Collections:||Dissertationen|
checked on Sep 30, 2020
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