Separation Of Mono Research Articles

Separation of Mono-, Di-, and Tristearin from an Industrial Mixture of Glycerides by Normal- and Reverse-Phase HPLC

Abstract This work reports on a quantitative and qualitative study of reverse and normal-phase HPLC to separate mono-, di-, and tristearin from an industrial mixture of glycerides. For normal-phase chromatography a CN-bonded packed column was used, while C8 and C18 columns were used for reverse-phase chromatography. Both types of chromatography were studied with UV and RI detection. The influence of some chromatographic factors, such as the bonded phase, mobile-phase composition, and flow rate, on the retention times, selectiveness, and effectiveness were studied.

Packed capillary HPLC: An attractive separation technique for small organic molecules

The feasibility of using packed capillary HPLC for the analysis of small organic molecules has been demonstrated by three examples: the separation of glucose and sucrose telomers, the separation of the different components of a solvent extraction reagent, and the separation of mono-, di-, and trioleins, all of which have been achieved with packed capillary columns of 0.32 mm inner diameter and eluent flow rates of 3 microliters per minute. Application to the analysis of the solvent extraction reagents has shown that this technique can be used as a quantitative tool in just the same way as any conventional HPLC method. The feasibility of a direct packed capillary HPLC – mass spectrometry interface has been demonstrated for the glucose telomer separation; direct coupling is only possible because of the microliter flow rates employed by the technique.

Chromatographic separation and partial identification of glycosidically bound volatile components of fruit

Synthetic monoterpenic and aromatic β- d-glucosides and β- d-rutinosides were separated by Fractogel TSK HW-40 S chromatography according to their molecular size and interactions occurring between the aglycone moiety and the gel matrix. Under these conditions terpenyl rutinosides were eluted before the homologous glucoside derivatives. In the two classes, monoglucosides and rutinosides, aromatic glycosidically bound components had lower retention times than the corresponding terpenyl components. The use of over-pressure layer chromatography (OPLC) allowed the separation of glucoside and rutinoside derivatives, and in these two classes aromatic and several monoterpene compounds were well separated. Based on these results, the separation of glycosidically bound volatile components isolated from grapes (Muscat of Alexandria) a and apricot (Rouge du Roussillon) was undertaken using a three-step process. Silica gel fractionation allowed the separation of mono- and diglycosidic fractions present in apricot. Fifteen peaks were obtained from grape extracts by Fractogel chromatography, and under the same conditions sixteen and eleven peaks were detected in monosaccharidic and disaccharidic fractions, respectively isolated from apricot. The glycosidic fractions isolated by gel chromatography were purified by preparative OPLC, and some of them were sufficiently pure for a subsequent structural analysis. Moreover, partial identification of glycosidically bound volatile components separated by these two methods may be achieved using retention data when standard compounds are available; on the other hand, enzymatic hydrolysis of the isolated pure fractions gives information in the absence of reference compounds.

Phosphorylation and inactivation of the pyruvate dehydrogenase from the anaerobic parasitic nematode, Ascaris suum. Stoichiometry and amino acid sequence around the phosphorylation sites.

Tryptic digestion of the fully phosphorylated Ascaris suum pyruvate dehydrogenase complex yielded a single tetradecapeptide containing 2 phosphorylated serine residues. Its amino acid sequence was Tyr-Ser-Gly-His-Ser(P)-Met-Ser-Asp-Pro-Gly-Thr-Ser(P)-Tyr-Arg and was very similar to one of the tryptic phosphopeptides isolated from mammalian and yeast pyruvate dehydrogenases. At partial phosphorylation, three peptides were isolated which corresponded to the monophosphorylated (sites 1 and 2) and diphosphorylated tetradecapeptides. In contrast to results reported from mammalian complexes, phosphorylation of the ascarid complex paralleled inactivation, and no additional phosphorylation occurred after inactivation was complete. Complete inactivation of the complex was associated with the incorporation of 1.7-1.9 mol of phosphoryl groups/mol of alpha-pyruvate dehydrogenase subunit, and the strict preference of the pyruvate dehydrogenase kinase for site 1 was not observed. Whereas site 1 was initially phosphorylated more rapidly than site 2, at 50% inactivation, 41% of the incorporated phosphoryl groups were incorporated into site 2. In addition, substantial amounts of peptide monophosphorylated at site 2 also accumulated, suggesting that prior phosphorylation at site 1 was not necessary for phosphorylation at site 2. Phosphorylation also caused a marked decrease in the mobility of the alpha-pyruvate dehydrogenase subunit on sodium dodecyl sulfate-polyacrylamide gels and the apparent separation of mono- and diphosphorylated forms of the enzyme. The significance of these observations in the regulation of the unique anaerobic mitochondrial metabolism of A. suum is discussed.

ChemInform Abstract: Preparation, Crystal and Molecular Structures, and Properties of Tetrabromo(1,5,9,13,17,21‐hexaazacyclotetracosane)dicopper(II) and Bromo(1,5,9‐triazacyclododecane)zinc(II) Bromide. Separation of Mono‐ and Binucleating Ligands by Selective Complexation.

AbstractThe macrocyclic ligands (24)aneN6 and (12)aneN3 are prepared as a 1:10 mixture in accordance with well‐documented methods.

Simultaneous determination of mono- and bivalent cations in environmental chemistry using isocratic ion chromatography

The influence of the pH of the mobile phase ethylenediamine (EDA)/citrate on the retention behaviour of mono- and bivalent cations on a silica based cationexchange stationary phase was studied. Variation of the pH-value was accomplished either by changing the concentration of one component of the eluent or by adding potassium hydroxide or hydrochloric acid to an eluent of fixed composition. The pH range between 2.8 and 3.0 proved to be most suitable for the separation of mono- and bivalent cations. Alkali metals, alkaline earths and transition elements could be separated in a single run. Extending the pH-range up to 5.2 showed the possibility of an additional determination of more strongly retained ions, such as Pb2+ or Sr2+.

High-performance liquid chromatography of sugars on a mixed cation-exchange resin column

The separation of mono-, di-, and trisaccharides on a cation-exchange 6% cross-linked resin column in the silver form ( HPX-65A) is described. Acid-catalysed hydrolysis of sugars at elevated column temperatures could be suppressed by partially converting the column into the lead( II) form. The selectivity can be influenced by varying the ratio of the counter-ions. The use of this column connected in series with a cation-exchange 8% cross-linked resin column in the lead( II) form enabled the separation ofsucrose, maltose, lactose, glucose, galactose, and fructose. The presence of the combinations maltotriose—sucrose and lactulose—glucose requires additional analysis on an unmodified HPX-65A column.

Rapid ion-exchange separation of human brain gangliosides

An extract of human brain gangliosides was separated on a Spheron 1000-DEAE spherous fine-grain macroporous glycolmethacrylate anion-exchanger. Linear gradient elution using ammonium acetate in methanol resulted in the complete separation of mono, di-, tri-, tetra- and pentasialogangliosides in 35 min at the load of 2.4 mg/ml of ion-exchanger. The ganglioside fractions thus obtained were characterized by thin-layer chromatography on silica gel. In conclusion, the scope of rapid separation of gangliosides is discussed, based on a combination of column chromatographic methods.

Normal-phase high-performance liquid chromatographic separation of non-derivatized ganglioside mixtures

A new analytical and semi-preparative high-performance liquid chromatographic method for the separation of a brain ganglioside mixture into individual components is described. Gangliosides were applied to a LiChrosorb-NH 2 column and eluted with the solvent system acetonitrile—phosphate buffer at different volume ratios and ionic strengths. The elution profile was monitored by flow-through the detection of UV absorbance at 215 nm. The separation of mono- to polysialogangliosides was performed in one step in a total elution time lower than 90 min and with high reproducibility.

Reversed-phase high-performance liquid chromatographic separation of the four monoiodoinsulins: effect of column supports, buffers and organic modifiers

The separation of mono- and diiodoinsulins has been performed using various C 18 columns (LiChrosorb and Vydac), organic modifiers (acetonitrile, 2-propanol and ethanol) and trialkylammonium buffers at various pH values. One system (LiChosorb—2-propanol—triethylammonium formate, pH 6.0) allows complete separation between unlabelled insulin, monoiodoinsulins and diiodoinsulins. The more- or-less reduced binding affinity of the reversed-phase high-performance liquid chromatographic purified tracers is most likely caused by column bleeding.

Separation of mono-, di-, and trihydroxy stereoisomers of bile acids by capillary gas-liquid chromatography

Capillary gas-liquid chromatographic separation was studied for the complete set of the 26 theoretically possible isomers of mono-, di-, and trihydroxylated 5 beta-cholanic acids, which differ from one another in the number, position, and configuration of hydroxyl groups at C-3, C-7, and/or C-12 in the nucleus, as well as for some of their related acids. The bile acid samples were chromatographed as their methyl ester-trimethylsilyl (TMSi) ether derivatives and analyzed on three capillary columns coated with nonpolar OV-1, slightly polar OV-17, and polar SP-2340 as liquid phases. The retention times on capillary gas-liquid chromatography (GLC) responded dramatically to the minor structural differences, and almost complete separation of the positional and stereochemical isomers was achieved by the combined use of SP-2340 and OV-17 (or OV-1) capillary columns.

Separation of mono- and disaccharides by high-performance liquid chromatography with a strong cation-exchange resin and an acetonitrile-rich eluent

Separation of mono- and disaccharides by high-performance liquid chromatography with a strong cation-exchange resin and an acetonitrile-rich eluent

Preparative purification and group separation of mono- and dinucleotides by combining charge-transfer and affinity chromatography

Preparative purification and group separation of mono- and dinucleotides by combining charge-transfer and affinity chromatography

Mechanism of zwitterion-pair chromatography : I. Nucleotides

The basis of retention of zwitterionic solutes in reversed-phase liquid chromatography in the presence of zwitterionic pairing agents has been studied using long-chain amino acids (11-aminoundecanoic acid, C11AA and 12-aminododecanoic acid, C12AA), a tripeptide (l-leucyl-l-leucyl-l-Leucine, LLL), and a long-chain diamine (1,10-diaminodecane, C10DA). The adsorption has been determined for each pairing agent under the conditions used for chromatography to show up any correlation between retention and surface concentration of the pairing agents. Eluents were water-methanol (88:12) or water-dimethylformamide (90:10) buffered with acetic acid-acetate, or phosphoric acid-phosphate in the pH range 3–7. The most characteristic feature of zwitterion-pair chromatography is the existence of maxima in retention of zwitterionic solutes at pH where both solute and pairing agent exist as zwitterions. With C11AA and C12AA as pairing agents this occurs at pH of 4.4 and with LLL as pairing agent at pH of 3.5. The peak in retention is most noticeable when the ionic strength of the buffer is small (in the millimolar-range). The pH behaviour of retention in the presence of zwitterionic pairing agents is in striking contrast to that in the presence of C10DA which not only provides much reduced retention when present at the same surface concentration of amino groups, but shows no marked dependence on pH.It is concluded that zwitterionic pairing agents provide a new mode of retention for zwitterionic solutes, namely the formation in the stationary phase of quadrupolar ion pairs between the zwitterionic forms of the solute and pairing agent when an appropriate pH is employed.Illustrative separations of mono-, di- and triphosphate nucleotides, and of selected monophosphate nucleotides are shown.

Determination of chlorinated phenols by high-performance liquid chromatography

The separation of mono-, di-, tri- and tetrachlorinated phenols and pentachlorophenol has been investigated by high-performance liquid chromatography using three different systems, adsorption chromatography on silica and reversedphase chromatography on a polar bonded phase (aminoalkyl) and a non-polar bonded phase (octadecyl). A satisfactory group separation as well as a satisfactory separation of isomers could not be obtained by adsorption chromatography on silica. A reasonable separation of isomers was obtained with amino columns, but the group separation was not satisfactory. The octadecyl columns were superior with reference both to separation of groups and of isomers within these groups as well as to stability and speed of analysis. A mixture of nineteen different phenols was resolved on a C 18 column with a 30-min linear gradient of 56–80% methanol and 44-20% of 0.02 M KH 2PO 4 (pH 4.0).

Separation of mono- and bis-phosphonium salts by preparative HPLC

Development and application of a preparative HPLC method for the separation of phosphonium salts is described. Analytical chromatograms obtained by means of ion-pair chromatography as well as adsorption chromatography in the presence or absence of acid are presented. A description of successful preparative separations is also given. The chromatographic fractions were identified by 1H- and 31P-NMR spectroscopy.

Separation of mono- and di-saccharide derivatives by high-resolution gas chromatography

The gas chromatographic analysis of NaBH4-reduced monosaccharide mixtures (either trimethylsilylated or acetylated) and NaBH4-reduced trimethylsilylated disaccharide mixtures in open tubular glass capillary columns is described. Complete separations of the investigated monosaccharides can be achieved if the same separation column and the appropriate method of derivatization are used. Kovats' retention indices of the derivatives are determined and their experimental repeatability is discussed.

Quantitative determination of several mono- and oligosaccarides in food products by means of high-pressure liquid chromatography replacement of the toxic eluent 'acetonitrile/water' by a mixture of harmless solvents

The toxic eluent mixture acetonitrile/water frequently used for separation of mono- and oligosaccarides is replaced by the harmless temary mixture acetone/ethyl acetate/water. By various techniques — degassing of the eluent, parallel connection of two columns and temperature control of the columns, of the eluate and RI-detector — the method is made suitable for the determination of lower saccharide concentrations than usual. Methods for rational preparation of samples — extraction of the saccarides, deionizing of the sample solution — are suggested. Based on examples, the efficiency of the method is demonstrated.

Separation of mono- and diolefins as methoxymercurated adducts by paper chromatography

Separation of mono- and diolefins as methoxymercurated adducts by paper chromatography

Separation of oligonucleotides on ion-exchange derivatives of spheron

Diphenylamine-formic acid hydrolyzate of Bacillus subtilis DNA (a mixture of pyrimidine oligodeoxyribonucleotides) was chromatographed using an ionic strength gradient on seven ion exchangers: five DEAE-Spherons 300 of various capacities, two types of BD-Spheron 300 and DEAE-Sephadex A-25. The suitability of ion-exchange derivatives of Spheron for the chromatography of oligonucleotides is discussed. The separation of mono- to undeca-deoxyribonucleotides was achieved.