Optimization and application of ICPMS with dynamic reaction cell for precise determination of (44)Ca/(40)Ca isotope ratios
ABSTRACT An inductively coupled plasma mass spectrometer with dynamic reaction cell (ICP-DRC-MS) was optimized for determining (44)Ca/(40)Ca isotope ratios in aqueous solutions with respect to (i) repeatability, (ii) robustness, and (iii) stability. Ammonia as reaction gas allowed both the removal of (40)Ar+ interference on (40)Ca+ and collisional damping of ion density fluctuations of an ion beam extracted from an ICP. The effect of laboratory conditions as well as ICP-DRC-MS parameters such a nebulizer gas flow rate, rf power, lens potential, dwell time, or DRC parameters on precision and mass bias was studied. Precision (calculated using the "unbiased" or "n - 1" method) of a single isotope ratio measurement of a 60 ng g(-1) calcium solution (analysis time of 6 min) is routinely achievable in the range of 0.03-0.05%, which corresponded to the standard error of the mean value (n = 6) of 0.012-0.020%. These experimentally observed RSDs were close to theoretical precision values given by counting statistics. Accuracy of measured isotope ratios was assessed by comparative measurements of the same samples by ICP-DRC-MS and thermal ionization mass spectrometry (TIMS) by using isotope dilution with a (43)Ca-(48)Ca double spike. The analysis time in both cases was 1 h per analysis (10 blocks, each 6 min). The delta(44)Ca values measured by TIMS and ICP-DRC-MS with double-spike calibration in two samples (Ca ICP standard solution and digested NIST 1486 bone meal) coincided within the obtained precision. Although the applied isotope dilution with (43)Ca-(48)Ca double-spike compensates for time-dependent deviations of mass bias and allows achieving accurate results, this approach makes it necessary to measure an additional isotope pair, reducing the overall analysis time per isotope or increasing the total analysis time. Further development of external calibration by using a bracketing method would allow a wider use of ICP-DRC-MS for routine calcium isotopic measurements, but it still requires particular software or hardware improvements aimed at reliable control of environmental effects, which might influence signal stability in ICP-DRC-MS and serve as potential uncertainty sources in isotope ratio measurements.
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ABSTRACT: Salinosporamide A (NPI-0052) is currently produced by a marine actinomycete, Salinispora tropica, via a saline fermentation process using a non-defined, commercially available synthetic sea salt, Instant Ocean. In order to control the consistency of the production of NPI-0052 and related analogs, two chemically defined salt formulations were developed to replace Instant Ocean. A chemically defined sodium-chloride-based salt formulation with similar sodium and chloride contents as in Instant Ocean was found to support higher production of NPI-0052 and a better metabolite production profile for downstream processing than Instant Ocean. A chemically defined sodium-sulfate-based salt formulation with low chloride concentration at 17 mM was found to support a similar NPI-0052 and metabolite production profile as Instant Ocean. The sodium-sulfate-based formulation is a robust formulation for large-scale production process due to its reduced corrosiveness in fermentation as compared with the saline fermentation utilizing Instant Ocean or the sodium-chloride-based salt formulation. The production of NPI-0052 in both chemically defined salt formulations was successfully scaled-up to a 42-l fermentor, indicating that these salt formulations can be used for large-scale manufacturing process.Applied Microbiology and Biotechnology 05/2008; 78(5):827-32. DOI:10.1007/s00253-008-1358-9 · 3.81 Impact Factor
Article: Atomic Spectroscopy[Show abstract] [Hide abstract]
ABSTRACT: Atomic spectrometry remains one of the most powerful methods for the determination of the elements and their compounds in a wide variety of types of samples and in widely differing concentrations. Innovation in the optical methods being atomic absorption, atomic fluorescence, and atomic emission spectrometry mainly with plasma sources as well as in the use of the same sources as ion sources for elemental mass spectrometry continued to be discussed worldwide in very well known international conferences. The results communicated are the best proof that atomic spectrometry is a very strong tool for addressing various analytical problems. In this review a representative part of the papers published in selected journals during the period of January 2010 to June 2012 dealing with analytical chemistry and spectrochemical analysis is discussed. Recent trends and instrumental developments are outlined.Analytical Chemistry 07/2008; 80(12):4317-47. DOI:10.1021/ac8006297 · 5.83 Impact Factor
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ABSTRACT: This review surveys the literature on reference materials for geological and environmental research for the two year period 2006–2007. In this time ca. 1200 publications appeared containing analytical data on reference materials, indicating that their importance for analytical work has been recognised by geochemists and environmental scientists. Although many reference materials exist, there remains a pressing need for further samples, especially for certified rock reference materials, homogeneous reference glasses, mineral reference materials and so-called delta-zero materials for normalisation purposes of stable isotopes. This review focuses on six topics: rock reference materials, reference materials for platinum-group elements, reference glasses, mineral reference materials, environmental reference materials (seawater, soil) and isotopic reference materials (radiogenic, stable isotopes). In addition, a short description is given of the GeoReM database for reference materials of geological and environmental interest, which contains analytical data from the publications discussed in this review.Geostandards and Geoanalytical Research 12/2008; 32(4). DOI:10.1111/j.1751-908X.2008.00916.x · 3.79 Impact Factor