Schneider David L.

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Schneider
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David L.
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  • Technical Report
    A self-powered pumping system for in situ extraction of particulate and dissolved materials from large volumes of seawater
    (Woods Hole Oceanographic Institution, 1982-02) Winget, Clifford L. ; Burke, John C. ; Schneider, David L. ; Mann, Don R.
    A pumping system has been developed for the in situ extraction of particles and of dissolved constituents from large volumes of seawater. The assembly consists of a battery-powered submersible pump, filters, and chemisorptive cartridges; it is entirely self-contained and has been used successfully on ship's hydrographic wire to depths as great as 5800 m. The pump is designed to operate at a maximum pressure drop of 66 cm of Hg; flow rates have varied from 1.3 to 5.1 liters/min. We have sampled volumes as large as 758 liters, and the measured battery drain suggests that volumes several times this could be pumped at any depth. The system is being used to study a variety of artificial radionuclides, but modifications of the filter or chemisorbent units would make it useful in many other geochemical applications.
  • Technical Report
    A method for the analysis of rare earth elements in natural waters by isotope dilution mass spectrometry
    (Woods Hole Oceanographic Institution, 1994-01) Schneider, David L. ; Palmieri, Julianne M.
    A method is described to measure rare-earth elements (REE) in natural water samples. An iron hydroxide precipitation followed by ion-exchange chromatography is used to concentrate and separate the REE from other matrix components. Additionally, the rare-earth elements themselves ar separated into the fractions using an organic acid with a second cation column. Instrumental detection is by isotope dilution mass spectrometry (IDMS) using either thermal ionization mass spectrometry (TIMS) or inductively coupled plasma-mass spectrometry (ICP-MS). Excellent precision is shown by many duplicate and replicate analyses. Blanks are 1-2% or less of samples.
  • Technical Report
    The determination of rare earth elements in marine sediments by ion-exchange separation and ICP emission spectrometry
    (Woods Hole Oceanographic Institution, 1987-12) Schneider, David L. ; Bankston, Donald C.
    A method has been developed to measure rare-earth elements (REE) in gram-sized marine sediment samples. A strong acid digestion technique followed by ion-exchange chromatography is used to solubilize, separate, and purify the REE from other matrix components. Instrumental detection is by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Excellent precision and accuracy were proved by analyses of unknown sediment replicates and standard reference rock samples. Blanks and empirically determined detection limits are discussed in relation to measured REE concentrations in sediments. Direct evidence is given for the co-precipitation and fractionation of the REE by precipitates formed as a result of the acid digestion with HF. A technique for dissolving these is then presented.
  • Preprint
    Examination of precipitation chemistry and improvements in precision using the Mg(OH)2 preconcentration inductively coupled plasma mass spectrometry (ICP-MS) method for high-throughput analysis of open-ocean Fe and Mn in seawater
    ( 2006-02-14) Saito, Mak A. ; Schneider, David L.
    The chemistry of magnesium precipitation preconcentration of Fe, Mn and Co from seawater was investigated, and this analytical technique was adapted for use with the Element-2 inductively coupled plasma mass spectrometer (E2 ICP-MS). Experiments revealed that the scavenging efficiency of Mn using the precipitation protocol described here was ~95% and similar to that previously observed with Fe. In contrast, the scavenging efficiency of Co was three-fold lower than that of Fe and Mn, resulting in poor recovery. An increase in sample size to 13mL led to several desired effects: 1) an increase in the Fe and Mn signals allowing a final dilution of samples to 0.5mL and the use of an autosampler, 2) an increase in precision to ~1-2.5% RSD, 3) an increase in signal relative to the blank. Experiments suggest metal concentration from seawater occurs during the formation of Mg(OH)2 precipitate, whereas P was scavenged by adsorption onto the Mg(OH)2 particles. Example vertical profiles are shown for dissolved Fe and Mn from the Equatorial Pacific.