Vanadium , in seawater

Emerson SR, Huested SS (1991) Ocean anoxia and the concentrations of molybdenum and vanadium in seawater. Marine Chem 34 177-196... 

Kiriyama and Kuroda [597] combined ion exchange preconcentration with spectrophotometry using 2-pyridylazoresorcinol in the determination of vanadium in seawater. 

Van den Berg and Huang [600] carried out direct electrochemical stripping of dissolved vanadium in seawater using cathodic stripping. Voltammetry was performed with a hanging mercury drop electrode. The detection limit was 0.3 nmol/1 after a collection period of 2 min. 

Vega and Van den Berg [601] determined vanadium in seawater in amounts down to 70 pM by absorptive stripping voltammetry. 

Two methods for the determination of vanadium in seawater have been developed which use neutron activation analysis and atomic absorption spectrome-... 

Although the neutron activation analysis is inherently more sensitive than the atomic absorption spectrometry, both procedures yield a reliable measurement of vanadium in seawater at the natural levels of concentration. 

Chappie and Byrne [743] applied an electrothermal vaporisation inductively coupled plasma technique to the determination of copper, cobalt, manganese, nickel, and vanadium in seawater in amounts down to 3-140 ppt. 

In a method for the determination of copper, nickel, and vanadium in seawater, Shijo et al. [840] formed complexes with 2-(5-bromo-2 pyridylazo)-5-(N-propyl-N-sulfopropylamino) phenol and extracted these from the seawater with a xylene solution of capriquat. Following back-extraction into aqueous sodium perchlorate, the three metals were separated on a C is column by HPLC using a spectrophotometric detector. 

Tunicates (ascidians or sea-squirts) are invertebrate marine organisms, which can accumulate vanadium at concentrations approaching 350 mM (the concentration of vanadium in seawater is 10 8 M). This vanadium is taken up as V(V) from seawater (Figure 17.16), reduced to oxidation state III or IV and stored in a soluble form in the blood cells within acidic vacuoles at concentrations a million fold higher than in their external surroundings. 

Van den Berg CMG, Zi QH (1984) Direct electrochemical determination of dissolved vanadium in seawater by cathodic stripping voltammetry with the hanging mercury drop electrode. Anal Chem 56 2383-2386... 

Trace amounts of vanadium have been found in meteorites and seawater, and it has been identified in the spectmm of many stars including the earth s sun. The occurrence of vanadium in oak and beech trees and some forms of aquatic sea life indicates its biological importance. 

Shriadah et al. [516] determined molybdenum VI in seawater by densitometry after enrichment as the Tiron complex on a thin layer of anion exchange resin. There were no interferences from trace elements or major constituents of seawater, except for chromium and vanadium. These were reduced by the addition of ascorbic acid. The concentration of dissolved molybdenum (VI) determined in Japanese seawater was 11.5 pg/1, with a relative standard deviation of 1.1%. 

Huang and Shih [616] used a graphite furnace atomic absorption spectrometer with a stabilised platform furnace involving atomisation from a graphite surface pretreated with vanadium to determine down to 24 ppt of zinc in seawater. 

Tominaga et al. [682,683] studied the effect of ascorbic acid on the response of these metals in seawater obtained by graphite-furnace atomic absorption spectrometry from standpoint of variation of peak times and the sensitivity. Matrix interferences from seawater in the determination of lead, magnesium, vanadium, and molybdenum were suppressed by addition of 10% (w/v) ascorbic acid solution to the sample in the furnace. Matrix effects on the determination of cobalt and copper could not be removed in this way. These workers propose a direct method for the determination of lead, manganese, vanadium, and molybdenum in seawater. 

Field et al. [747] used ICP high-resolution mass spectrometry to determine vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium, and lead in seawater. Each analysis required 50 p,l sample and a 6 minute analysis time. 

Alves et al. [744] determined vanadium, nickel, and arsenic in seawater in the 10-20 000 ppt range using flow injection cryogenic desolvation ICP-MS. 

The ascidians or tunicates (sea squirts) accumulate vanadium from seawater (about 5x 10-8 mol dm-3) to a level of about 1 mol dm-3 and store it in a dilute solution of sulfuric acid (pH<2) in blood cells called vanadocytes. The tunicates thus concentrate vanadium several million-fold. 079 NMR, ESR and EXAFS determinations on whole vanadocyte cells of Ascidia ceratodes and Ascidia nigra indicate that the vanadium is present mainly as aquated V111 probably complexed with sulfate. Some vanadyl ion (5-10%) is also present.1080 1081... 

Ascidians or tunicates (Phylum Chordata) belong to the class of Ascidiacea and are common marine animals whose body is enclosed in a jacket or tunic. The animals are attached to rocks and are either solitary or colonial. They continuously filter seawater to obtain minute organisms and particulate organics. As was originally discovered by Henze the animals concentrate vanadium from seawater to levels about 10 times that present in seawater (35 nM), a phenomenon that has attracted considerable interest. The transition metal is present... 

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