Acute and chronic exposure to arsenic is a growing problem in the industrialized world. Arsenic is a potent carcinogen and
toxin in humans. In the body, arsenic is metabolized to produce several species, including inorganic forms, such as trivalent
(AsIII) and pentavalent (AsV), and the methylated metabolites such as monomethylarsonic acid, (MMAV), and dimethylarsinic acid (DMAV), in addition to arsenobetaine (AsB) which is ingested and excreted from the body in the same form. Each of these species
has been reported to possess a specific but different degree of toxicity. Thus, not only is the measurement of total As required,
but also quantification of the individual metabolites is necessary to evaluate the toxicity and risk assessment of this element.
There are a large number of reference materials that are used to validate methodology for the analysis of As in blood and
urine, but they are limited to total As concentrations. In this study, the speciation of five arsenic metabolites is reported
in blood and urine from commercial available control materials certified for total arsenic levels. The separation was performed
with an anion exchange column using inductively coupled plasma mass spectrometry as a detector. Baseline separation was achieved
for AsIII, AsV, MMAV, DMAV, and AsB, allowing us to quantify all five species. Excellent agreement between the total arsenic levels and the sum of the
speciated As levels was obtained. 相似文献
An automated sequential injection (SI) on-line solvent extraction-back extraction separation/preconcentration procedure is described. Demonstrated for the assay of cadmium by electrothermal atomic absorption spectrometry (ETAAS), the analyte is initially complexed with ammonium pyrrolidinedithiocarbamate (APDC) in citrate buffer and the chelate is extracted into isobutyl methyl ketone (IBMK), which is separated from the aqueous phase by means of a newly designed dual-conical gravitational phase separator. A metered amount of the organic eluate is aspirated and stored in the PTFE holding coil (HC) of the SI-system. Afterwards, it is dispensed and mixed with an aqueous back extractant of dilute nitric acid containing Hg(II) ions as stripping agent, thereby facilitating a rapid metal-exchange reaction with the APDC ligand and transfer of the Cd into the aqueous phase. The aqueous phase is separated in a second dual-conical gravitational phase separator, and 30 μl of it is entrapped and metered in a sample loop (SL) and subsequently introduced via air segmentation into the graphite tube for analyte quantification. The ETAAS determination is performed in parallel with the separation/preconcentration process of the ensuing sample. An enrichment factor of 21.4, a detection limit of 2.7 ng l−1, along with a sampling frequency of 13 h−1 were obtained at a sample flow rate of 6.0 ml min−1. The precision (R.S.D.) at the 0.4 μg l−1 level was 1.8% as compared to 3.2% when quantifying the organic extractant directly. The applicability of the procedure is demonstrated for the determination of trace levels of cadmium in three certified reference materials. 相似文献
A chitosan resin functionalized with 3-nitro-4-amino benzoic acid moiety (CCTS-NABA resin) was newly synthesized for the collection/concentration of trace molybdenum by using cross-linked chitosan (CCTS) as base material. The carboxyl group of the moiety was chemically attached to amino group of cross-linked chitosan through amide bond formation. The adsorption behavior of molybdenum as well as other 60 elements on the resin was examined by passing the sample solutions through a mini-column packed with the resin. After the elution of the elements collected on the resin with 1 M HNO3, the eluates were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and atomic emission spectrometry (ICP-AES).
The CCTS-NABA resin can adsorb several metal ions, such as vanadium, gallium, arsenic, selenium, silver, bismuth, thorium, tungsten, tin, tellurium, copper, and molybdenum at appropriate pHs. Among these metal ions, only molybdenum could be adsorbed almost completely on the resin at acidic regions. An excellent selectivity toward molybdenum could be obtained at pH 3–4. The adsorption capacity of CCTS-NABA resin for Mo(VI) was 380 mg g−1 resin. Through the column pretreatment, alkali and alkaline earth metals in river water and seawater samples were successfully removed.
The CCTS-NABA resin was applied to the adsorption/collection of molybdenum in river water and seawater samples. The concentrations of molybdenum in river water samples were found in the range of 0.84 and 0.95 ppb (ng g−1), whereas molybdenum in seawater was about 9 ppb. The validation of the proposed method was carried out by determining molybdenum in the certified reference materials of SLRS-4, CASS-4, and NASS-5 after passing through the CCTS-NABA resin; the results showed good agreement with the certified values. 相似文献
The composition range and (composite modulated) structure of compounds within the wide range non-stoichiometric LaSb2Snx, 0.1?x?0.75, solid solution is carefully investigated via a combined electron diffraction, XRD and electron probe microanalysis study. Evidence for metastability of the LaSb2Snx phase at the low x composition end of the solid solution is presented. Direct evidence is found for a reasonably (although by no means perfectly) well ordered Sn sub-structure which is, in general, mutually incommensurable with respect to a very well ordered underlying LaSb2 sub-structure along both a and c directions. The overall (3+2)-d superspace group symmetry is given along with a discussion of the consequences as regards the arrangement of the Sn atoms. The Sn sub-structure c-axis cell dimension shows very little variation with composition x providing direct experimental evidence of the importance of Sn-Sn metallic bonding (along one-dimensional [001] Sn strings) for the stability of the phase. 相似文献
Magnetic measurements onHeusler alloys (Co,T)2XY (field and temperature dependence) are performed around theCurie points (temperature range:TC–50 toTC+50). A method otherwise used to get rid of ferromagnetic impurities only (g versus 1/H plot) is applied to pure ferromagnets and yields completely new g (extrap.) versusT curves with a maximumTmax>
TC. The method was applied to pure gadolinium first which has aCurie point within the accessible region of the susceptibility measuring device. 相似文献