Elemental speciation and trace metal analysis using chemical separations interfaced to inductively coupled plasma - mass spectrometry.

摘要

A comparison of capillary electrophoresis (CE) migration times using standard on-column UV detection and inductively coupled plasma - mass spectrometry (ICP-MS) is presented for two different CE separations. The first is a separation of five arsenic compounds, four anionic species and one neutral, using reverse polarity in a chromate buffer with an electroosmotic flow modifier. The second CE separation employs normal polarity for the separation of eleven lanthanide cations using a HIBA buffer with an indirect UV detection reagent. Migration times observed for CE-ICP-MS electropherograms are comparable to migration times acquired with UV detection, and may be adjusted by changes in the makeup liquid level position. The precision of peak areas (2%) and migration times (4%) obtained using CE-ICP-MS is comparable to that obtained using online UV absorbance detection. CE-ICP-MS limits of detection are in the low ng ml−1 range for the analytes studied. Then, CE is coupled on-line to a double-focusing sector field inductively coupled plasma-mass spectrometer (DF-ICP-MS) for the analysis of mixtures of lanthanide elements in aqueous samples with natural isotope abundances and in a sample taken from an irradiated tantalum target particle reactor containing artificial nuclide abundances. Detection limits for the most abundant isotopes of lanthanides were 0.1 ppb to 5 ppb, an improvement of as much as one order of magnitude compared to a quadrupole ICP-MS system. Abundances for the most abundant isotopes of lanthanides were found to be within 0.1–2% of table values for natural samples while isotopes present in smaller amounts were within 3–5% of table values. CE-ICP-MS is also used for the chiral speciation of DL-selenomethionine using Marfey's reagent for chiral derivitization and applied to selenized yeast samples extracted with proteinase K.; Finally, two anion exchange chromatography systems were interfaced to ICP-MS for determination of bromate in ozonated drinking waters and arsenic in environmental waters. As part of rigorous method validation studies, possible chromatographic and spectral ICPMS interferences were investigated, method detection limits determined, laboratory fortified blanks confirmed, and laboratory fortified matrices were analyzed. Each system was tested with sample matrices from water utilities sent from different areas in the United States and met USEPA performance criteria for the similar methodology.