scholarly journals Quantitative determination of the spring entropy effect and its indication of the conformational change of polymer coils with varying concentration in aqueous poly(N-isopropylamide) solutions

RSC Advances ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 5540-5549
Author(s):  
Li Song ◽  
Jiaxiang Lin ◽  
Panpan Liu ◽  
Jingqing Li ◽  
Shichun Jiang ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Quantitative Determination ◽  
Conformational Change ◽  
Entropy Effect ◽  
Polymer Coil

Entropy effect is deduced from the distinctive demixing enthalpy behavior in different concentration regions of PNIPAM aqueous solution and interpretated as the conformational change of polymer coil.

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

Perchlorate in Sea Water

1961 ◽  
Vol 41 (1) ◽  
pp. 175-186 ◽  
Author(s):  
R. Greenhalgh ◽  
J. P. Riley
Keyword(s):  
Aqueous Solution ◽  
Quantitative Determination ◽  
Water Sample ◽  
Coefficient Of Variation ◽  
Sea Water ◽  
Absorption Spectrophotometry ◽  
Infra Red ◽  
Tetraphenylarsonium Chloride

The use of tetraphenylarsonium chloride for the detection and determination of perchlorate in sea water has been investigated. An aqueous solution of this reagent gives a visible precipitate of tetraphenylarsonium perchlorate with sea water containing 5 μg ClO4-/ml. within 10 min. For the quantitative determination of traces of perchlorate, potassium perrhenate is added to the water sample, and the tetraphenylarsonium perrhenate, which is precipitated by addition of the reagent, co-precipitates tetraphenylarsonium perchlorate. Perchlorate is determined in the mixed precipitate by infra-red absorption spectrophotometry. Using 100 ml. of sea water, a sensitivity of 0·03 μg ClO4-/ml. can be attained, with a coefficient of variation of ca. 10%. No interference is caused by the ions normally present in sea water.

Gravimetric Determination of Ethoxylated Mono- and Diglycerides in Bread

1981 ◽  
Vol 64 (6) ◽  
pp. 1462-1464
Author(s):  
James F Lawrence ◽  
Jagannath R Iyengar ◽  
Harry B S Conacher
Keyword(s):  
Aqueous Solution ◽  
Fatty Acids ◽  
Quantitative Determination ◽  
Petroleum Ether ◽  
Gravimetric Method ◽  
Phosphomolybdic Acid ◽  
Barium Ions ◽  
Gravimetric Determination ◽  
Ether Extraction

Abstract A gravimetric method is described for the quantitative determination of ethoxylated mono- and diglycerides (EMGs) in bread at levels as low 0.42% (dry sample). The air-dried pulverized samples are Soxhlet-extracted 22 h with an azeotropic mixture of n-propanol-water. The contents are evaporated to dryness, and then treated with 5% HCl in methanol to trans-esterify the fatty acids present which are then removed by petroleum ether extraction. The EMGs are subsequently precipitated from aqueous solution with phosphomolybdic acid in the presence of barium ions. The precipitate is weighed and compared with known amounts of standard carried through the same procedure.

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