Quantitative Determination of Aqueous Dodecatungstophosphoric Acid Speciation by NMR Spectroscopy

2004 ◽  
Vol 57 (3) ◽  
pp. 261 ◽  
Author(s):  
Bradley J. Smith ◽  
Vincent A. Patrick
Keyword(s):  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Quantitative Determination ◽  
Intermediate Species ◽  
High Concentration ◽  
Stable Intermediate ◽  
Ph Range

The speciation and equilibria during base decomposition of α-[PW12O40]3– have been determined using 31P and 183W NMR spectroscopy over the pH range 0.7–13.5. NMR spectroscopy was used to directly observe the polytungstate species in aqueous solution at high concentration (0.25 mol L–1) and follows the progressive decomposition of [PW12O40]3– to WO42– and PO43–. It was found unexpectedly in the pH range 1.2–2.3 that [PW12O40]3– did not decompose directly to [PW11O39]7– but first formed an equilibrium with [P2W18O62]6–, [P2W21O71]6–, and some new, stable, intermediate species before converting into α-[PW11O39]7–.

Quantitative Determination of Sodium Dodecatungstosilicate Speciation by 183W Nuclear Magnetic Resonance Spectroscopy

2002 ◽  
Vol 55 (4) ◽  
pp. 281 ◽  
Author(s):  
B. J. Smith ◽  
V. A. Patrick
Keyword(s):  
Aqueous Solution ◽  
Nuclear Magnetic Resonance ◽  
Nmr Spectroscopy ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
High Concentration ◽  
Ph Range ◽  
Nuclear Magnetic

The speciation and equilibria of sodium dodecatungstosilicate has been determined using 183W nuclear magnetic resonance (NMR) spectroscopy over the pH range 3-13.5. The use of NMR allowed the direct observation of polytungstate anions in aqueous solution and at high concentration (0.5 mol L-1). Using this technique, the speciation of α-[SiW12O40]4-, α-[SiW11O39]8-, α-[NaSiW11O39]7-, α-[H2W12O40]6-, [H8W11O40]6-, [H7W11O40]7-, [W7O24]6-, [H2W12O42]10-, and WO42- was quantified as a function of pH. This work has allowed stability constants for α-[SiW12O40]4- (log K 46) and α-[SiW11O39]8- (log K 86) to be estimated.

Quantitative Determination of Sodium Metatungstate Speciation by 183W N.M.R. Spectroscopy

2000 ◽  
Vol 53 (12) ◽  
pp. 965 ◽  
Author(s):  
Bradley J. Smith ◽  
Vincent A. Patrick
Keyword(s):  
Aqueous Solution ◽  
Quantitative Determination ◽  
Direct Observation ◽  
Solubility Product ◽  
High Concentration ◽  
Kinetics Of ◽  
Paratungstate B

The speciation and equilibria of sodium metatungstate, Na6[H2W12O40], has been determined by a combination of 183W n.m.r. spectroscopy and gravimetry over the p[H] range 4.5–10.0. The use of n.m.r. spectroscopy allowed the direct observation of polytungstate anions in aqueous solution and high concentration (0.25 mol l–1). Sodium metatungstate, with the progressive addition of base, was found to decompose to paratungstate A, [W7O24]6–. Paratungstate A then slowly converted to paratungstate B, [H2W12O42]10–. The kinetics of equilibrium was found to be slow, requiring up to 8 months to stabilize. With the addition of further base paratungstate B decomposed to orthotungstate, WO42–. Logarithmic constants (logK) for these transformations were determined as 195, 20 and 118, respectively. The solubility product for sodium paratungstate B was determined to be 6.89 ( 0.80) 10–6.

Quantitative Determination of Krill Oil Composition by ATR-FTIR, NIR, and 31P NMR Spectroscopy

2020 ◽  
Author(s):  
Ashraf Ismail ◽  
Sanaz Molaye Moghaddam ◽  
Jean-Pierre MetabanzoulouSarya Aziz ◽  
Jacqueline Sedman ◽  
Mazen Bahadi
Keyword(s):  
Nmr Spectroscopy ◽  
Quantitative Determination ◽  
31P Nmr ◽  
31P Nmr Spectroscopy ◽  
Krill Oil ◽  
Oil Composition

Natural abundance 13C-NMR spectroscopy for the quantitative determination of fecal fat

2003 ◽  
Vol 36 (7) ◽  
pp. 505-510 ◽  
Author(s):  
P Kunz ◽  
B Künnecke ◽  
I Kunz ◽  
H Lengsfeld ◽  
M von Kienlin
Keyword(s):  
Nmr Spectroscopy ◽  
Quantitative Determination ◽  
13C Nmr ◽  
13C Nmr Spectroscopy ◽  
Natural Abundance ◽  
Fecal Fat

Determination of Carbaryl Residues in Honey Bees

1965 ◽  
Vol 48 (4) ◽  
pp. 771-774
Author(s):  
D P Johnson ◽  
H A Stansbury
Keyword(s):  
Aqueous Solution ◽  
Acetic Acid ◽  
Quantitative Determination ◽  
Honey Bees ◽  
Methylene Chloride ◽  
Hydrolysis Product ◽  
Separate Analysis ◽  
Yellow Substance ◽  
Hydrolysis Of

Abstract A method has been developed for detecting residues of carbaryl (1-naphthyl methylcarbamate) as well as its hydrolysis product, 1-naphthol, in dead bees. The method is based on extraction of the bees with benzene, followed by a cleanup involving liquid partitioning and chromatography on Florisil. The quantitative determination involves hydrolysis of carbaryl to 1-naphthol and coupling of the latter with p-nitrobenzenediazonium fluoborate in acetic acid to form a yellow substance. For separate analysis, free 1-naphthol is separated from methylene chloride into a basic aqueous solution. The sensitivity of the method is about 0.1 ppm; recoveries averaged 85.6 ± 6.6% for 1- naphthol and 83.8 ± 2.7% for carbaryl.

Ultraviolet Spectroscopic Determination of Five Lanthanide Elements without Prior Separation

1993 ◽  
Vol 47 (6) ◽  
pp. 764-772 ◽  
Author(s):  
Irvin M. Citron ◽  
Patrick M. Hanlon ◽  
Stephen Arthur
Keyword(s):  
Aqueous Solution ◽  
Quantitative Determination ◽  
Heavy Metal Ions ◽  
Lanthanide Ions ◽  
Ion Concentrations ◽  
Statistical Reliability ◽  
Modified Method ◽  
Lanthanide Elements ◽  
The Individual

This investigation has resulted in an analytical method for the quantitative determination of total lanthanide concentration in aqueous solution by absorbance at 240 nm in the ultraviolet followed by quantitative determination of individual lanthanide ion concentrations by the use of concentration-responsive absorption peaks in the 190–235 nm region. The 240-nm peak is present and is proportional to concentration regardless of the ligand employed to complex the lanthanides (including H2O). The individual lanthanide/ligand peaks in the 190–235 nm region were selected on the basis of their separation from one another, their linearity of absorbance vs. concentration, and their statistical reliability based on replicate sample analyses. Lanthanides involved in this investigation were La+3, Nd+3, Eu+3, Ho+3, and Yb+3. Ligands ultimately selected for complexation were citrate for La+3, Nd+3, and Ho+3, and DTPA for Eu+3, Ho+3, and Yb+3. When large amounts of heavy metal ions were present, a modified method was developed with citrate as the only complexing ligand for all five lanthanides. The method here developed permits the analyses of lanthanide ions in aqueous solution without prior separation and involves the use of comparatively inexpensive instrumentation (UV absorption spectrophotometer).

Quantitative determination of thiourea in aqueous solution in the presence of sulphur dioxide by Raman spectroscopy

The Analyst ◽  
1986 ◽  
Vol 111 (5) ◽  
pp. 539 ◽  
Author(s):  
Heather J. Bowley ◽  
Elizabeth A. Crathorne ◽  
Donald L. Gerrard
Keyword(s):  
Aqueous Solution ◽  
Raman Spectroscopy ◽  
Quantitative Determination ◽  
Sulphur Dioxide
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