Identical Chromatograms Research Articles

Use of Dual Detection in the Gas Chromatographic Analysis of Oleaginous Biomass Feeds and Biofuel Products To Enable Accurate Simulated Distillation and Lipid Profiling

This contribution describes the development of a chromatographic method capable of simultaneously identifying and quantifying the constituents found in oleaginous biomass—including algae oil—and in biofuel samples through a single cost-effective analysis. Major constituents of the aforementioned analytes include oxygen- and/or nitrogen-containing compounds along with fuel-like hydrocarbons. A novel simulated distillation gas chromatographic (SimDist) technique including dual detection capabilities—specifically flame ionization (FID) and mass spectrometry (MS)—produced identical chromatograms with perfectly aligned signals. FID chromatograms afforded excellent quantitative data while the corresponding MS spectra enabled accurate and thorough compound identification. Simulated distillation data displayed a remarkably linear relationship between retention time and the boiling point of heteroatom-containing compounds in addition to n-alkanes. Indeed, although standard SimDist data were calibrated using the bo...

Potentiostatic and Galvanostatic Modulation of Liquid Chromatography

Simplified versions of the chromatographic column in electrochemically modulated liquid chromatography were possible. A two electrodes design had a good response to changes in potential, yet excluding the need for an external reference electrode, supporting electrolyte, and porous stainless steel. The cell constants for both the two and three electrodes designs were similar. The incorporation of the reference electrode into the PVC joint of the column body resulted in fast potential equilibration times, where about a 50% decrease in the cell constant was observed using this new modification. Both the two- and the new three- electrode designs resulted in self contained, rigid, and reliable columns that can be safely dry stored; no porous stainless steel was a necessary material for the counter electrode. Galvanostatic, rather than potentiostatic, modulation of separations was successful. Interestingly, both the two and three electrode designs resulted in identical chromatograms when the same current was used. These results suggest that the simple two electrode design with regular, rather than porous, stainless steel as the counter electrode has the same performance as that of the three electrode design, which requires an external reference electrode, external supporting electrolyte, as well as a porous stainless steel counter electrode.

Temperature programming and gradient elution in reversed-phase chromatography with packed capillary columns

The two major anisocratic elution modes were compared in reversed-phase chromagraphy with 180 μm I.D. fused-silica capillary columns acked with 6 μm Zorbax SB ODS-silica. By evaluating the retention factors of alkylbenzenes at acetonitrile concentrations varying from 60 to 80% (v/v) in the aqueous eluent and in the temperature range of 30–80°C, it was found that a 5°C change in column temperature and a 1% change in acetonitrile concentration have almost the same effect on retention. This is illustrated by the almost identical chromatograms of an alkylbenzene sample obtained by temperature programming and by gradient elution under the same conditions otherwise and by simulation of the trajectories of the eluent peaks moving down the column. The results suggest that in reversed-phase HPLC with packed capillary columns temperature programming offers an alternative to gradient elution in a relatively narrow range of the required elution strength. Thermodynamic data from isocratic chromatographic measurements were used to predict the retention times of alkylbenzenes in reversed-phase chromatography with temperature programming at different heating rates and column inlet pressures. Temperature programming was used to separate β-lactoglobulins A and B by reversed-phase chromatography. It was also employed concomitantly with gradient elution to enhance the separation of a mixture of four standard proteins. The results indicate that temperature programming could serve as an adjunct to gradient elution by means of fine retention tuning to bring about or increase the resolution of closely related macromolecules.

Immunoreactive vasopressin in end stage renal failure

Patients with end stage renal failure have been shown to have higher basal concentrations of plasma arginine vasopressin than subjects with normal renal function. Immunoreactive vasopressin was detected in plasma from patients with severe chronic renal failure and a healthy subject at an elution volume identical to that previously determined with synthetic vasopressin. Assay of all fractions yielded identical chromatograms in the renal failure and healthy control groups. We conclude that the plasma immunoreactive vasopressin in end stage renal failure plasma coelutes with synthetic vasopressin and that the elevated concentrations found in these patients are not due to non-specific depression of binding in the vasopressin radioimmunoassay by circulating substances in renal failure.

Optical resolution of amino acids, peptides and hydroxycarboxylic acids using a new chiral column for ligand-exchange chromatography

The enantiometric resolution of amino acids, amino acid derivatives, peptides and hydroxycarboxylic acids was investigated using a chiral column of the ligand- exchange type. It was found that this column separated all of these compounds satisfactorily. Columns containing either a d- or l-ligand gave almost identical chromatograms, except that the retention order for a pair of chiral isomers was reversed. These columns could be applied to resolve simultaneously ten different types of dL- amino acids. Optically active impurities present in d and l-amino acids could be determined at concentrations down to about 100 ppm.

Gas Chromatographic Characterization of Porcine and Human Strains Belonging to The Mycobacterium Avium‐Intracellulare Complex

Trifluoroacetylated whole-cell methanolysates of 23 strains designated as belonging to the Mycobacterium avium-intracellulare complex by biochemical, growth chromogenicity and chicken pathogenicity tests, were analysed by gas chromatography. Twenty of the strains were isolated from pigs and the remainder from human beings. Serological typing showed that 13 of the porcine strains, but none of the human strains, belonged to M. avium. The remaining strains, except one which showed autoagglutination, did not react with antisera to M. avium (serotypes 1-3), thus suggesting that they belonged to M. intracellulare. Five different, highly reproducible chromatographic patterns, the main peaks of which were considered as representing bacterial carbohydrates and fatty acids, could be distinguished by visual examination and by cluster analysis. The chromatographic results could not be correlated with those obtained from serotyping of the strains studied. Mycobacteria recovered from different organs of one and the same pig gave virtually identical chromatograms. The strains isolated from three human beings had a chromatographic pattern which was identical with one of those produced by the porcine strains. The present investigation indicates that the gas chromatographic analytic technique used differentiates bacteria within the M. avium-intracellulare complex, without assigning the organisms to species.

Corrections

Abstract Volume 19 p 152: There are errors in the placement of two closed parentheses in the equation that follows equation 6. It should read K([Agi] - [Agi](B/F)/(B/F + 1)) x ([Abi - [Agi](B/F)/(B/F + 1)) = [Agi](B/F)/(BfF + 1) These errors were pointed out by Drs. C. L. Partain (Imaging Division) and John E. Hammond (RIA-Endocrine Laboratory) of the School of Medicine, the University of North Carolina, Chapel Hill, N. C., who supplied a detailed mathematical derivation of the equation, which is available on request either directly to them or to the Editorial Office of this journal. The first equation in the right-hand column was corrected in a subsequent reprinting. It should read: logit (Y) = loge [Y/100 - Y] = a + b logaX. This error was detected by D. Rodbard (NIH) and E. A. Sugden (Animal Diseases Research Institute, Hull, Quebec). Volume23 p 1398: The last two sentences in the paragraph on Tumor Extracts are incomplete. The sentence should read "The tissue is homogenized and then centrifuged to give a clear supernatant fluid, which is deproteinized either by precipitation with sulfosalicylic acid (50 g/liter) or by passage through an ultraffiter that retains compounds with molecular weight exceeding 1000 (Type PSAC; Millipore Corp.). Both procedures gave identical chromatograms. The deproteinized extract is applied directly to the column." p 515: footnote 1: Remove the words "current address." Mr. Canos was (and is) at this address when the work was begun.

Pyrolysis-Gas Chromatographic Analysis of Black Paints

Samples of 79 black paints from 27 manufacturers in the United States were examined to determine the extent to which paints can be distinguished by pyrolysis-gas chromatography. Evaluation by a Carbowax column showed some differences among paints from different manufacturers and among batches of paints from the same manufacturer. However, it was not possible to conclude that paints with identical chromatograms had a common origin.

Chromatographic Separation and Bioassay of the Gentamicin Complex

The gentamicin complex consists of three components, C1, C1a, and C2, which are separated by paper chromatography using the lower phase of a solvent system of chloroform, methanol, and 17% ammonia (2:1:1). Two identical chromatograms are developed. On one, the positions of these components at Rf's of approximately 0.75, 0.35, and 0.50, respectively, are located by means of ninhydrin. On the other, corresponding areas are cut out, eluted from the paper with 0.1 M potassium phosphate buffer, pH 8.0, and assayed microbiologically. This procedure determines the relative amounts of the three gentamicin fractions, and is superior to the original official FDA procedure that measured only two fractions.

Standardization of Methyl Green for Specific Staining of Egg-shell Material in a Trematode

ABSTRACT 1. The specificity of a number of samples of methyl green for egg-shell material in Fasciola hepatica was investigated. 2. A method for distinguishing between specific and non-specific stains by paper chromatography is described. 3. Specific stains gave almost identical chromatograms with an Rf value of 0 83 for both green and violet constituents. Non-specific samples gave chromatograms with an Rf of 0·65 for the green constituent and an Rf of 0·84 for the violet constituent. The liquid phase used was a mixture of organic solvents in the following proportions: ethanol, 100; water, 80; n-butanol, 100; cellosolve, 100. 4. The application of this technique has led to the production of a methyl green, named Methyl Green M.2, specific for shell material in Fasciola.

The occurrence of heartwood crystals in certain timbers

Crystals of a very characteristic shape and colour have been observed in the heartwood of 52 species form 19 different families. They are quite distinct in composition and appearance from the crystals of calcium oxalate that occur in the wood of many timbers, and they have never been seen in sapwood. The crystals appear first in the ray cells, where these are in contact with a vessel element. The area in which the crystals occur extends through all the tissues of the heartwood. The shape they take is partially dependent on the tissue in which they occur. They have frequently been found in close association with fungal hyphae. Their distribution has been studied intensively in Eucalyptus hemiphloia F. Muell. and E. sideroxylon A. Cunn., in which species they occur from the pith to a short distance from the outer edge of the heartwood and from the base of the tree to the upper limit of the heartwood. In a random selection of discs from other species of the genus Eucalyptus the crystals have a similar distribution within the heartwood. The crystals in E. hemiphloia have given identical chromatograms with crystals of ellagic acid, and it is probable that crystals in other Myrtaceae are of a similar nature. Further research is needed for identification of the fungi with which these crystals are associated, and to determine the chemical composition of the crystals and of the heartwood extractives of the woods in which they occur.

Fluorescence of amino-acids, peptides and amines on filter paper.

THE fluorescence of amino-acids and peptides on dry filter paper1 is of great value for locating these substances after paper chromatography, and has been found useful in quantitative work2 since it avoids destructive treatment with reagents such as ninhydrin. It also enables substances to be eluted for further investigations from sheets of chromatograms where gross irregularity of solvent flow renders the use of marker strips3 inaccurate as guides for cutting. Unfortunately, marked variations in fluorescence are often observed when identical chromatograms are run on sheets of No. 4 Whatman paper from different packets of papers or even on adjacent sheets from the same packet4, and batches of papers are occasionally encountered on which no fluorescence at all can be observed at normal nitrogen-levels. As Phillips1, quoting De Ment5, considered fluorescence of amino-acids on paper to be due to excitation of the acids themselves by ultra-violet light, it seemed possible that some impurity present in ‘bad’ fluorescent papers might therefore be quenching fluorescence. Sheets from a particularly bad batch of No. 4 Whatman paper could not be improved, however, by washing with water, dilute sodium hydroxide, hydrochloric acid or with solutions of 8-hydroxyquinoline or dithizone.