Hiroo Wada

Polymer-coated synthetic fibers designed for miniaturized sample preparation process

Miniaturized sample preparation technique for complex sample matrices has been developed with a polymer-coated fibrous extraction medium. Several hundreds of fine fibrous materials were packed longitudinally into a fused-silica capillary followed by a polymeric coating on it to prepare the extraction capillary. The extraction capillary was installed in a liquid chromatograph as a sample loop of the injection valve. The on-line coupled sample preparation/separation system demonstrated a good validity for the analysis of phthalates in real river and wastewater samples. The lowest limits of quantification for several phthalates were less than 1 ng/ml. The effect of polymeric coating to the filaments on the extraction power was also investigated.

Polymer-coated fibrous extraction medium for sample preparation coupled to microcolumn liquid-phase separations

Polymer-coated fibrous material has been introduced as the extraction medium for a miniaturized sample preparation method being coupled with microcolumn liquid chromatography. The preconcentration and the subsequent liquid chromatographic separation of tricyclic antidepressants (TCAs) drugs, amitriptyline, imipramine, nortriptyline and desipramine, was carried out with the hyphenated system. Several basic experimental parameters, such as extraction and separation conditions, were investigated along with the applicability of the method for the analysis of biological fluids. The results clearly showed that the on-line coupled system could be a powerful tool for the analysis of complex mixtures in biological matrix without a large solvent consumption and specially designed instruments. The lowest limit of quantification was quite acceptable for the analysis of TCAs in clinical and forensic situations.

High-performance gel filtration of water-soluble samples on polyvinyl alcohol columns

Abstract The chromatographic behaviour in aqueous solution of pullulans, polyethylene glycols, peptides and proteins with different molecular weights on newly developed polyvinyl alcohol columns (Asahipak GS column series: GS-310, GS-320, GS-510 and GS-520) has been investigated. Pullulans and polyethylene glycols eluted according to the gel filtration mode, so both series of compounds produced almost equal calibration curves for GS-310 and GS-320 and for GS-510 and GS-520; the exclusion limits on GS-310 and GS-320 and on GS-510 and GS-520 were found to be ca. 40,000 and 300,000, respectively. Peptides and proteins were found to adsorb slightly on the columns. However, the plots of the elution volumes against the logarithm of the molecular weights for many of the substrates tested gave rise to the linear calibration curves. Recovery of several crude proteins was also studied for the columns and high values were obtained (81–100%). The effects of changes in the flow-rate, temperature and concentration of electrolytes added to the eluents, on the retention of all four types of compound are also reported.

Behaviour of single-stranded oligodeoxyribonucleotides on a deae-5pw anion-exchange column

Abstract The separation of large, single-stranded oligodeoxyribonucleotides, prepared by chemical synthesis, was carried out on a DEAE-5PW anion-exchange column with eluents containing only volatile salts. It was found that gradient elution is essential and that a high resolution can be achieved at elevated temperatures ( ca. 50°C). Also, neutral pH of the eluents was found to be desirable for the separation. Under optimum conditions, a linear relationship between the elution volumes and the number of bases in the substrates was observed.

Matrix effect on the retention in reversed-phase liquid chromatography

SummaryA 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.

Chromatographic Characteristics of Pva Column

Abstract The retention behavior of polyethylene glycols, carbohydrates, peptides and pyrimidine and purine bases on a newly developed PVA gel column was examined. It has been found that separation was governed by a combined mode consisting of several known factors and dependent on the type of the sample and the nature of the eluent.

Retention mechanism of nucleotides, nucleosides and their bases on polyvinyl alcohol

Abstract The basic chromatographic properties of a polyvinyl alcohol (PVA) column material were investigated. By pH titration it was found that the PVA gel surface was negatively charged. The chromatographic behaviour of nucleotides on the gel was compared with that on an ODS column and found to be similar. However the behaviour of nucleosides bases were quite different from that on the ODS column. Since the retention characteristics of both types of solutes on the PVA column could be explained reasonably by the solvophobic theory, this result may suggest that the behaviour of these solutes on the ODS column is unusual. The difference in retention between AMP isomers and cAMP can be explained by the differences in their conformations.

Separation of single-stranded oligonucleotides on polyvinyl alcohol gel column

SummarySeparation mechanisms for single-stranded oligodeoxyribo-or oligoribonucleic acid fragments were explored on an Asahipak polyvinyl alcohol gel column (GS-320) by use of sequential isomers of such molecules. Substrates having different base numbers were found to be separated by size-exclusion chromatography while those having the same numbers with different base sequences were isolated by use of the reversed-phase mode. By using those dual modes, a limit for the separation of the samples was found to arise because one mode shifted the peaks of the substrates in the sense opposite to the shift resulting from the other mode and it was found that when substrates had less than nine bases, the solutes eluted separately.