Determination of Trace Metal (Mn, Fe, Ni, Cu, Zn, Co, Cd and Pb) Concentrations in Seawater Using Single Quadrupole ICP-MS: A Comparison between Offline and Online Preconcentration Setups (original) (raw)
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Journal of Analytical Atomic Spectrometry, 1988
The remarkable detection power of inductively coupled plasma mass spectrometry (ICP-MS) was demonstrated b y the analysis of an open ocean sea water reference material (with the acronym NASS-2). A 50-fold pre-concentration of several trace metals in the sea water was realised b y their adsorption o n t o silica-immobilised 8-hydroxyquinoline, which separates the elements of interest f r o m the bulk of the alkali and alkaline earth elements. The isotope dilution technique was used for the determination of seven elements (Ni, Cu, Zn, Mo, Cd, Pb and U). Accurate results were obtained for all of these elements except for Mo, with concentrations ranging between 0.027 and 11.5 pg 1-1.
Large programs in chemical oceanography currently require the determination of multiple trace elements in hundreds to thousands of open ocean seawater samples. For example, the international GEOTRACES program would benefit greatly from rapid, precise, automated, multi-element analytical methods for multiple trace metals in seawater. An automated, on-line extraction, flow-injection ICP-MS method is presented here for simultaneous determination of Mn, Fe, Co, Ni, Cu and Zn in open ocean seawater samples. A fully automated commercially available system buffers the pH of the samples on-line and extracts the metals of interest from 9 mL of seawater onto a chelation resin column, which is then eluted (1.6 M HNO3) directly into a magnetic sector ICP-MS. The resulting transient peaks elute in 45 μL (~30 s) yielding a preconcentration factor of ~200, and the total analysis cycle requires 8.75 min per sample. Elemental concentrations are calculated from integrated peak areas using a combination of isotope dilution and matrix-matched standard curves. Procedural blanks determined at periodic intervals (every 10 samples) throughout each sample run are used for blank correction and for calculating detection limits (range 0.3 to 16 pmol kg−1 seawater for these elements). Replicate analyses of a Ross Sea in-house consistency standard and four GEOTRACES reference seawater materials (Atlantic and Pacific, surface and deep water) are used to demonstrate precision of 1–3% (RSD) and very good agreement with reference consensus values for all elements except Co. Determined Co concentrations are ~40% lower than consensus values, consistent with the presence of strong Co ligands in seawater, and the absence of a UV-oxidation step in this method. As illustrated by oceanographically consistent profiles at the GEOTRACES Atlantic and Pacific baseline stations, this method provides highly precise measurement of trace metals over the full range of concentrations occurring in the global ocean. Moreover, the full methodology, including flow-injection hardware and control software, is readily transferable to other users.
Analytica Chimica Acta, 2011
A simple and accurate low-blank method has been developed for the analysis of total dissolved copper, cadmium, lead, and iron in a small volume (1.3-1.5 mL per element) of seawater. Pre-concentration and salt-separation of a stable isotope spiked sample are achieved by single batch extraction onto nitrilotriacetate (NTA)-type Superflow ® chelating resin beads (100-2400 beads depending on the element). Metals are released into 0.1-0.5 M HNO 3 , and trace metal isotope ratios are determined by ICPMS. The benefit of this method compared to our previous Mg(OH) 2 coprecipitation method is that the final matrix is very dilute so cone-clogging and matrix sensitivity suppression are minimal, while still retaining the high accuracy of the isotope dilution technique. Recovery efficiencies are sensitive to sample pH, number of resin beads added, and the length of time allowed for sample-resin binding and elution; these factors are optimized for each element to yield the highest recovery. The method has a low procedural blank and high sensitivity sufficient for the analysis of pM-nM open-ocean trace metal concentrations. Application of this method to samples from the Bermuda Atlantic Time-Series Study station provides oceanographically consistent Cu, Cd, Pb, and Fe profiles that are in good agreement with other reliable data for this site. In addition, the method can potentially be modified for the simultaneous analysis of multiple elements, which will be beneficial for the analysis of large number of samples.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2017
Analytical procedure for the determination of fourteen rare earth elements (REEs) in the seawater samples has been developed and validated. The elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) at ultratrace level were measured by high resolution sector field inductively coupled plasma mass spectrometry (HR ICP-SFMS) after off-line analytes pre-concentration and matrix separation. The sample pre-treatment was carried out by commercially available automated system seaFAST-pico™, which is a low-pressure ion chromatography technique, based on solid phase extraction principles. Efficient elimination of seawater matrix and up to 50fold pre-concentration of REEs enabled their accurate and precise quantification at ng L −1 level. A validation approach in line with the requirements of ISO/IEC 17025 standard and Eurachem guidelines were followed. With this in mind, selectivity, working range, linearity, recovery (from 92% to 102%), repeatability (1%-4%), intermediate precision (2%-6%), limits of detection (0.001-0.08 ng L −1) were systematically assessed. The total uncertainty associated to each result was estimated and the main sources of uncertainty sorted out. All major contributions to the combined uncertainty of the obtained results were identified and propagated together, following the ISO/GUM guidelines. The relative expanded uncertainty was estimated at range from 10.4% to 11.6% (k = 2). Demonstration of traceability of measurement results was also presented. Due to the low limits of detection, this method enables the determination of ultra-low levels of REEs in the open seawater as well as small variations in their concentrations. The potential of the proposed analytical procedure, based on combination of seaFAST-pico™ for sample preparation and HR ICP-SFMS, was demonstrated by direct analysis of seawater form different regions of the world.
Journal of Analytical Atomic Spectrometry, 1999
Concentrations of Mn, Ni, Cu, Zn and Pb in natural waters were measured by inductively coupled plasma mass spectrometry (ICP-MS) with on-line preconcentration using Toyopearl TSK-immobilized 8-hydroxyquinoline resin columns and ultrasonic nebulization. Trace metal concentrations, quantified after analyzing calibration standards, were measured in 3 mL samples in under 15 min with better than 5% precision. Method detection limits were 0.26, 0.86, 1.5, 10 and 0.44 ng L−1 for Mn, Ni, Cu, Zn and Pb, respectively. The accuracy of the method was demonstrated by results from runs of certified reference materials SLRS-3 and CASS-3, which have very different ionic strengths. This on-line system was successfully applied to measure water column trace metal concentrations in Galveston Bay, Texas, and the results compared favorably with those obtained using state-of-the-art off-line preconcentration techniques.
Determination of trace metals in sea water by ICP-MS after matrix separation
Acta Chimica …, 2003
The analysis of ultra trace elements in sea water samples is one of the most difficult analytical tasks in the field of environmental monitoring, as extremely low detection limits for elements buried in a highly saline matrix is required. The use of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for direct sea water analysis is currently limited by spectral and non-spectral interferences caused by the sea water matrix. Sample dilution is always a way out at the expense of inadequate sensitivity after such dilution especially for open ocean sea water. In order to approach this complex analytical task by ICP-MS there are two common strategies studied so far: first the use of pre-concentration technique and matrix removal and second the use of double focussing ICP-MS instruments. The use of Ammonium tetramethylene dithiocarbamate (APDC)/Methyl isobutyl ketone (MIBK) solvent extraction for matrix removal and direct estimation of trace elements in sea waters by ICP-MS are discussed in this paper.
Analytica Chimica Acta, 2010
Trace elements often limit phytoplankton growth in the ocean, and the quantification of particulate forms is essential to fully understand their biogeochemical cycling. There is presently a lack of reliable measurements on the trace elemental content of marine particles, in part due to the inadequacies of the sampling and analytical methods employed. Here we report on the development of a series of stateof-the-art trace metal clean methods to collect and process oceanic particulate material in open-ocean and sea ice environments, including sampling, size-fractionated filtration, particle digestions and analysis by magnetic sector inductively coupled plasma-mass spectrometry (ICP-MS). Particular attention was paid to the analysis of certified reference materials (CRMs) and field blanks, which are typically the limiting factor for the accurate analysis of low concentrations of trace metals in marine particulate samples. Theoretical detection limits (3 s of the blank) were low for all 17 elements considered, and varied according to filter material and porosity (sub-g L −1 for polycarbonate filters and 1-2 g L −1 for quartz and polyester filters). Analytical accuracy was verified using fresh water CRMs, with excellent recoveries noted (93-103%). Digestion efficiencies for various acid combinations were assessed using sediment and plankton CRMs. Using nitric acid only, good recoveries (79-90%) were achieved for Mo, Cd, Ba, Pb, Mn, Fe, Co, Ni, Cu, Zn and Ga. The addition of HF was necessary for the quantitative recovery of the more refractory trace elements such as U, Al, V and Cr. Bioactive elements such as P can also be analysed and used as a biomass normaliser. Our developed sampling and analytical methods proved reliable when applied during two major field programs in both the open Southern Ocean and Antarctic sea ice environments during the International Polar Year in 2007. Trace elemental data are presented for particulate samples collected in both suspended and sinking marine material, and also within sea ice cores.