Gas chromatographic retention characteristics of low molecular weight methylpolysiloxanes part III. Structural identifications of polycyclic methylpolysiloxanes based on logarithmic plots of retention data on two phases

1974 ◽  
Vol 7 (5) ◽  
pp. 225-228 ◽  
Author(s):  
G. Alexander ◽  
G. Garzó
Keyword(s):  
Molecular Weight ◽  
Chromatographic Retention ◽  
Low Molecular Weight ◽  
Retention Data ◽  
Retention Characteristics ◽  
Two Phases

scholarly journals The separation and sequencing of permethylated peptides by mass spectrometry directly coupled to gas-liquid chromatography

1976 ◽  
Vol 157 (3) ◽  
pp. 777-780 ◽  
Author(s):  
J D Priddle ◽  
K Rose ◽  
R E Offord
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Chemical Ionization ◽  
Chromatographic Retention ◽  
Gas Liquid Chromatography ◽  
Retention Data ◽  
Primary Sequence ◽  
Peptide Derivatives ◽  
Derivatives Of

The use of g.l.c. coupled to mass spectrometry to separate and sequence permethylated acetyl- and trifluoroacetyl-peptides in a single operation is described. Both electron impact and chemical ionization were used to induce fragmentation, and the latter was found to be more sensitive. Chromatographic retention data are presented which suggest that peptide derivatives of molecular weight of at least 750 are accessible to the technique. The application of our methods to the determination of the primary sequence of proteins is discussed.

Correlation Between GC Retention Data and Relative Molecular Weight of N,N-Bis(2,2,2-trifluoroethyl)dithiocarbamates of Some Divalent Metals

1996 ◽  
Vol 61 (11) ◽  
pp. 1609-1614 ◽  
Author(s):  
Ján Hrouzek ◽  
Ján Krupčík ◽  
Ivan Skačáni
Keyword(s):  
Molecular Weight ◽  
Correlation Coefficients ◽  
Retention Indices ◽  
Chromatographic Retention ◽  
Retention Data ◽  
Capillary Gc ◽  
Data Retention ◽  
Divalent Metals ◽  
Relative Molecular Weight ◽  
Linear Retention Indices

The correlation of gas-chromatographic retention data (retention times and linear retention indices) and relative molecular weight was examined for N,N-bis(2,2,2-trifluoroethyl)dithiocarbamate chelates of some divalent metals. Regression analysis of data obtained by capillary GC on a non-polar column heated by applying a dual-ramp temperature programme gave linear dependences possessing reasonable correlation coefficients.

Gas-Chromatographic Identification of Urinary Carbohydrates Isolated by Anion-Exchange Chromatography

1970 ◽  
Vol 16 (8) ◽  
pp. 722-725 ◽  
Author(s):  
W C Butts ◽  
R L Jolley
Keyword(s):  
Molecular Weight ◽  
Anion Exchange ◽  
Anion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Chromatographic Retention ◽  
Retention Data ◽  
Methylene Unit ◽  
Trimethylsilyl Derivatives ◽  
Chromatographic Peaks ◽  
Anion Exchange Separation

Abstract More than 40 chromatographic peaks representing carbohydrates have been separated from human urine by a carbohydrate analyzer that makes use of anion-exchange chromatography. Ten of these separated carbohydrates have been identified by gas chromatography of their trimethylsilyl derivatives, which were formed by reaction with N-trimethylsilylimidazole. The borate buffer from the anion-exchange separation was removed from the samples before the derivatives were made. Gas-chromatographic retention data have been determined for 37 carbohydrates, including pentoses, hexoses, hexosamines, disaccharides, and trisaccharides, and are tabulated as methylene unit (MU) values. These various classes of carbohydrates elute within distinct MU regions, generally in the order of increasing molecular weight. More than one peak is obtained for those sugars existing in more than one anomeric form.

A high-performance oil-free backing pump for electron microscopes

1978 ◽  
Vol 36 (1) ◽  
pp. 110-111
Author(s):  
G.K.W. Balkau ◽  
E. Bez ◽  
J.L. Farrant
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Hot Spots ◽  
High Performance ◽  
Carbonaceous Material ◽  
Contamination Rate ◽  
Low Molecular Weight ◽  
Principal Source ◽  
Rotary Pumps ◽  
Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Low-molecular-weight heparin in the prevention and treatment of thromboembolic disorders

1998 ◽  
Vol 1 (5) ◽  
pp. 166-174 ◽  
Author(s):  
Evelyn R Hermes De Santis ◽  
Betsy S Laumeister ◽  
Vidhu Bansal ◽  
Vandana Kataria ◽  
Preeti Loomba ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Low Molecular Weight ◽  
Prevention And Treatment
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