Vinyl Alcohol Copolymer Gel Research Articles

Single-step synthesis of [ 18F]haloperidol from the chloro-precursor and its applications in PET imaging of a cat's brain

We have established a convenient synthesis process for the synthesis of [ 18F]haloperidol using a single-step 18F - for - Cl exchange reaction and a new elution system for the preparative high performance liquid chromatography (HPLC) using C18 bonded vinylalcohol copolymer gel (ODP) and a basic eluent. We successfully applied the product to cat-PET study and got clear images of the striatum, showing the usefulness of this synthesis.

Rapid and Efficient Synthesis of High-Purity Fluorine-18 Labeled Haloperidol and Spiperone via the Nitro Precursor in Combination with a New HPLC Separation Method

Abstract We have completed a convenient synthesis of fluorine-18 labeled butyrophenone neuroleptics from their nitro precursors. Thus, we have developed an efficient single-column HPLC system using a C18-bonded vinyl alcohol copolymer gel (octadecyl polymer, ODP) column and strongly alkaline solvent systems for purifying of the 18F-labeled butyrophenone neuroleptics obtained by a single-step 18F-for-nitro exchange reaction. The method has been applied to the synthesis of two typical butyrophenone neuroleptics ([18F]haloperidol and [18F]spiperone) with high purity in high yield. With information concerning the optimized conditions for the 18F-for-nitro exchange reaction, the synthetic method would be useful for synthesizing various 18F-labeled compounds.

High-performance liquid chromatographic separation of kyotorphin, a basic Tyr-Arg dipeptide, in rat brain tissue and quantification using fluorimetric detection.

Two HPLC procedures based on sample derivatization at the N-terminal Tyr moiety with agents yielding fluorescent derivatives were applied to the selective and sensitive detection as well as quantification of the basic kyotorphin, Tyr-Arg dipeptide, in rat brain tissue. The first one is a post-column fluorescence derivatization method, whereby the peptides extracted from the brain tissue are separated on an octadecylsilyl-silica gel column, followed by on-line fluorescence derivatization for detection. The other one is a pre-column derivatization method, where the extracted peptides are first reacted with fluorogenic agents at the N-terminal Tyr moiety to their corresponding fluorescent derivatives, subsequently separated on an octadecyl-poly(vinyl alcohol) copolymer gel column, and signal responses are measured fluorimetrically. Both methods permitted the quantification of the synthetic kyotorphin added to the rat brain tissues. The concentration range of kyotorphin-like biogenic peptide was 60-100 pmol/g in the cortex, striatum and hypothalamus tissues.

Ultraviolet detection of peptides by reversed-phase liquid chromatography using an in-line reactor containing copper metal

A general method has been developed for the selective ultraviolet detection of peptides using reversed-phase liquid chromatography. The method is based on the formation of copper(II)-peptide complexes by the reaction of peptides with copper(II) ions in an alkaline mobile phase through an in-line reactor containing copper metal. Amino acid, di-, tri- and tetra peptides used as model compounds (leucine, glycylleucine, leucylglycylglycine and alanylalanylalanylalanine) are separated on a column containing C 18-bonded vinyl alcohol copolymer gel (Asahipak ODP-50, 5 μm, 150 mm × 6 mm i.d.) and an alkaline mobile phase (pH 11.0, 25 mM phosphate buffer). A detection limit of 200 pg ( S N = 3 ) was obtained for alanylalanylalanylalanine.

Coulometric Detection of Peptides by Reversed-Phase Liquid Chromatography Using an In-Line Reactor Containing Copper Metal

A general method has been developed for the selective coulometric detection of peptides using reversed-phase liquid chromatography. This method is based on the formation of electrochemically oxidizable copper(II)-peptide complexes by the reaction of peptides with copper(II) ions in an alkaline mobile phase through an in-line reactor containing copper metal. Di-, tri- and tetrapeptides used as model compounds (6 species) are separated on a column containing CIS-bonded vinyl alcohol copolymer gel (Asahipak ODP-50,5 μm, 150 mm×6 mm i.d.) and an alkaline mobile phase (pH 11.0, 25 mM phosphate buffer). A detection limit of 3 ng was obtained for alanylalanylalanylalanine.

Coulometric detection of peptides by reversed-phase liquid chromatography with a solid-phase reactor containing copper metal

A general reversed-phase liquid chromatographic method with coulometric detection for the determination of peptides has been established using a solid-phase reactor containing copper metal. The method is based on the formation of electrochemically oxidizable copper(II)-peptide complexes by the reaction of peptides with copper(II) ions in an alkaline mobile phase through the solid-phase reactor. Di- and tripeptides used as model compounds (6 species) are separated on a column contained C 18-bonded vinyl alcohol copolymer gel (Asahipak ODP-50, 5μm, 250 mm × 6.0 mm i.d.) and an alkaline mobile phase (pH 11.0, 40 mM borate buffer). A detection limit of 5 ng was obtained for alanylalanylalanine

Simultaneous Determination of Purine and Pyrimidine Bases Using High-Performance Liquid Chromatography with Electrochemical Detection: Application to DNA Assay

Abstract A sensitive method for simultaneous determination of purine and pyrimidine bases was developed using high performance liquid chromatography with electrochemical detection (ECD). Pyrimidines as well as purines were detectable by ECD under alkaline conditions, and the order of susceptibility to electrochemical oxidation was guanine > adenine > thymine > cytosine. These bases were separated on a vinyl alcohol copolymer gel column and determined by ECD. The detection limit for each base was picomole level. This method was applied to the quantitation of bases in the acid hydrolysates of DNA and oligodeoxy-nucleotides.

Peptide behaviour and analysis on a chemically stable C 18-bonded vinyl alcohol copolymer column with alkaline and acidic eluents

C 18-bonded vinyl alcohol copolymer (ODP) gel showed no weight loss or decrease in column efficiency for alkyl alcohols after being immersed in aqueous solutions of pH 2 and 10 at 50°C for 48 h, and only a 1% weight loss and a slight decrease in alkyl alcohol retention volumes after similar immersion at pH 13. The chemical stability of the ODP gel was further demonstrated in analyses of acidic, neutral and basic peptides on an ODP column with eluents of pH 3–10, which showed that the peptides differ considerably in the sensitivity of their retention behaviour to eluent pH, even though hydrophobic interaction invariably appeared to be the main retention mechanism. The ODP column was therefore applied to the analysis and alignment of lysil-endopeptidase (LEP) peptides derived from reduced and S-carboxymethylated carboxyl proteinase (Rcm-P-CP) of Pseudomonas sp. 101. One acid-soluble and seven alkaline-soluble LEP peaks were found in analyses on the ODP column using acidic and alkaline eluents, respectively. The chymotryptic peptides of Rcm-P-CP were first separated on an ODS column with an acidic eluent, and the eight elutes which contained lysine residue, as determined by amino acid analysis, were then analysed on the ODP column with an alkaline eluent, resulting in a further separation of each into several peaks and thus in the recovery of fractions of pure peptides. The LEP peptide alignment was then determined by overlapping the sequences of the chymotryptic peptides with the C- and N-terminal regions of the LEP peptides.

Chromatographic characteristics of nucleic acid components on vinyl alcohol copolymer gel columns

The chromatographic characteristics of nucleic acid components on an Asahi-pak GS-320 vinyl alcohol copolymer gel column were investigated in comparison with those on an ODS column. On both columns the order of elution within each class (nucleotide, nucleoside or nucleic acid base) was generally pyrimidine compounds followed by purine compounds, the only exception being the late elution of thymine from the GS-320 and, particularly, from the ODS column. Between the three classes of nucleic acid components, the two columns exhibited different elution orders. On the GS-320 column, the order was consistently nucleotide, nucleoside and base, i.e., in order of increasing water solubility, with a consistent correlation between capacity factors ( k′) and Hansch's log P values, showing that hydrophobic adsorption between the gel and the base group is the predominant separation mechanism for both the nucleosides and the bases. In the separation of nucleotides on the GS-320 column, an ion-repulsion interaction appeared to be predominant, as the k′ values were negative and the retention volumes were increased by methylation of the carboxylic groups in the gel but unaffected by additionof acetonitrile to the mobile phase. On the strongly hydrophobic ODS column, nucleoside elution occurred after nucleotide and base elution and more complex correlations were observed, suggesting hydrophobic interaction of the octadecyl group of the gel with the sugar group and also with the base group, particularly for the nucleosides. This interference was supported by an observed increase in the capacity factor of ribose in the presence of antichaotropic sodium chloride on the ODS but not on the GS-320 column. The utility of the GS-320 column for the separation of nucleic acid components was also investigated. Nucleotides, nucleosides and bases were consistently separated, apparently by a hydrophobic adsorption mechanism, permitting the simple, efficient analysis of mixtures of these substances by isocratic elution.

Selectivity of an octadecyl-modified vinyl alcohol copolymer gel for the retention of polar compounds

The enthalpies of phenols and aromatic acids were measured in order to characterize their behaviour on an octadecyl-bonded vinyl alcohol copolymer gel in reversed-phase liquid chromatography. These values were compared with the enthalpies measured on an octadecyl-bonded silica gel. The enthalpies of non-polar compounds, measured on an octadecyl-bonded silica gel, were higher than those obtained on the bonded vinyl alcohol copolymer gel. However, the enthalpies of phenols and aromatic acids were higher than those obtained on an octadecyl-bonded silica gel. This means that hydrogen bonding may be involved in the retention of phenols and aromatic acids on this vinyl alcohol copolymer gel.

Chromatographic properties of a vinyl alcohol copolymer gel column for the analysis of non-ionic surfactants

A high-performance size-exclusion chromatographic column packed with Asahipak GS-310 vinyl alcohol copolymer gel was investigated for its applicability to the analysis of non-ionic surfactants with mobile phases containing water and aceto-nitrile or other organic solvents in various ratios. The surfactant series consisted of R(OCH 2CH 2) n OH, where R is an alkylaryl group and n = 1–100. In the water-rich region, with acetonitrile concentrations of 0–30%, surfactants either were not eluted or their elution was extremely delayed, indicating a hydrophobic interaction between the gel and the alkylaryl group in the surfactant. In the acetonitrile-rich region, with acetonitrile concentrations of 60–100%, the surfactants were eluted relatively rapidly in order of decreasing molecular weight, without a fine separation between compounds with different n values. These results indicate that the organic solvent effetively inhibited the hydrophobic interaction and that size exclusion was the predominant separation mechanism. In the intermediate region, with 30–60% acetonitrile concentrations, the surfactants were eluted in the same order as for the acetonitrile-rich region, but less rapidly and with a fine separation between n values. The results indicate that the separation mechanism is mainly hydrophobic interaction between the alkylaryl groups and the gel, the hydrophobicity of the gel being too weak for effective interaction with the oxyethylene groups. The results indicate that the Asahipak GS-310 hydrophilic polymer gel column can be effectively employed for the practical, efficient high-performance liquid chromatographic analysis of non-ionic surfactants.

Separation of peptides by multimode chromatography on a column packed with vinyl alcohol copolymer gel

Several mechanisms of peptide separation in high-performance liquid chromatography were observed to occur on the Asahipak ® GS-320 packed with vinyl alcohol copolymer. Neutral rather than acidic mobile phases were employed as they were found to result in higher retention of many peptides on the GS-320. For neutral peptides, the retention volume corresponded to the Rekker's hydrophobic fragmental constant, with a correlation coefficient of 0.71. Peptides with acidic residues eluted early, as an effect of ionic exclusion; those with basic residues were retained longer, owing to an ion-exchange effect. The ionic interactions were shown to involve the car☐ylic group present on the gel polymer. The net result was found to be excellent separation of hydrophilic as well as hydrophobic peptides, related to differences in their isoelectric points. The combination of these complex mechanisms, together with the size-exclusion effect of the GS-320 gel for separation of proteins and other large molecules and for analysis with a mobile phase high in acetonitrile content, makes possible high-resolution isocratic analysis of peptides, which cannot be achieved on octadecylsilica or ion-exchange columns.

High-performance liquid chromatography of gluco-oligomers on C 18-bonded vinyl alcohol copolymer gel with alkaline eluents

High-performance liquid chromatography of gluco-oligomers on C 18-bonded vinyl alcohol copolymer gel with alkaline eluents

Retention of aromatic acids on an octadecyl-bonded vinyl alcohol copolymer gel

The selectivity of an octadecyl-bonded vinyl alcohol copolymer gel was examined by investigating the chromatographic behaviour of aromatic acids. The energy effect on the retention of aromatic acids was calculated from the result for alkylphenols. This packing was less hydrophobic than octadecyl-bonded silica gels, and the energy effect on the retention of aromatic acids was small compared to the values measured on an octadecyl-bonded silica gel. The correlation coefficient between the energy effects of aromatic acids measured on the octadecyl-bonded vinyl alcohol copolymer and silica gels was 0.972 ( n  36). However, this bonded organic packing had more selectivity for the retention of ortho-substituted alkylbenzoic acids.

Selectivity of hydrophobic compounds on an octadecyl- bonded vinyl alcohol copolymer gel

The selectivity of an octadecyl-bonded vinyl alcohol copolymer gel was examined by investigating the difference in the enthalpy effect for alkylbenzenes, alkanes, alcohols and polyaromatic hydrocarbons. The retention of these compounds on an octadecyl-bonded silica gel decreased as the column temperature increased. However, their chromatographic behaviour on an octadecyl-bonded vinyl alcohol copolymer gel was not simple. The values of the enthalpy effect for aliphatic compounds were positive above 35°C, negative below 35°C and small at low temperatures, which indicates that the structure of the stationary phase was somehow changed at ca. 33°C. Polyaromatic hydrocarbons were selectively retained on this octadecyl-bonded vinyl alcohol copolymer gel.

Retention of Phenols on an Octadecyl-Bonded Vinylalcohol Copolymer Gel

The chromatographic behavior of phenols was studied on an octadecyl-bonded vinylalcohol copolymer gel in acidic acetonitrile/water mixtures. The energy effect of phenols was measured on octadecyl-bonded silica gels where the values of alkylbenzenes were used as the standard instead of polyaromatic hydrocarbons. The selectivity within their isomers was larger on the octadecyl-bonded vinylalcohol copolymer gel than that measured on octadecyl-bonded silica gels. The correlation coefficient between the energy effects of phenols measured on the octadecyl-bonded vinylalcohol copolymer gel and those measured on an octadecyl-bonded silica gel was 0.685 (n=13) for alkylphenols and 0.392 (n=20) for halogenated phenols due to the selectivity of the vinylalcohol copolymer gel. Halogenated phenols were retained more on the organic polymer gel, and the average value of the energy effects was 50% less than the values obtained on the inorganic gel.

Development of a c 18-bonded vinyl alcohol copolymer gel for reversed-phase high-performance liquid chromatography

The fundamental characteristics of a polymer-based C 18 gel developed for reversed-phase high-performance liquid chromatography were investigated. The octadecyl polymer (ODP) gel obtained by introduction of octadecyl groups in place of the hydroxy groups of vinyl alcohol copolymers was packed into a 150 mm x 6 mm I.D. column and the performance was compared with that of commercial polystyrene and ODS gels. The ODP gel displayed excellent tolerance towards acidic, alkaline and buffered eluents, with little of the shrinkage and swelling shown by conventional polystyrene and modified polystyrene gels with varying eluent polarity, thus making it appropriate for a wide range of eluents, including water, ethanol and acetonitrile. The ODP column exhibited a theoretical plate number with alkyl alcohol standards that was higher than those of most ODS columns, and showed none of the adsorption and peak tailing that tend to occur with basic substances on ODS columns, owing to the complete absence of residual silanol groups in the ODP gel.

Matrix effect on the retention in reversed-phase liquid chromatography

A polymer-based, reversed-phase column (VA-C18), prepared by grafting octadecyl chain onto vinyl alcohol copolymer gel, was investigated for its chromatographic characteristics. n-Alkanes and n-alkyl alcohols were found to be retained only by hydrophobic interaction between the solutes and the octadecyl chain. In the case of aromatic hydrocarbons, in addition to the hydrophobic interaction, π-π interaction between the solutes and the based material was elucidated to contribute to the retention. For aromatic tertiary amines which are known to strongly interact with the residual silanol group of the silica-based reversed-phase columns to produce broadened and skewed peakes, the VA-C18 column also retained these substrates strongly by the combination of hydrophobic, π-π, and ionic interactions. In this case, however, symmetrical peaks were observed. From these results, it was determined that in the case of VA-C18, the base material was found not to produce undesirable effect although the solutes interact with the base. Further conclusion obtained was that in reversed phase liquid chromatography, chromatographic properties of base matrix is highly responsible for the overall retention.