Spherical polyimide (PI) particles have been introduced as a stationary phase in liquid chromatography (LC). The PI was prepared with the starting materials of pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (4,4'-oxydianiline, ODA), resulting the spherical PI (PMDA-ODA type) particles with an average diameter of about 5 μm. The synthesized PI particles were packed into a conventional blank LC column having a typical size of 4.6 mm i.d, 150 mm length, and the retention behavior for a group of polycyclic aromatic compounds (PACs) was evaluated in LC. The retention behavior was compared with that obtained on a commercially-available octadecylsilica (ODS) phase. The results indicated a significantly larger retentivity of PACs on the PI stationary phase than that on typical ODS stationary phases, where the retention tendency on the PI phase for various PACs having different molecular size and shape was similar to the trend on the ODS phase. The large retention on the PI phase can be interpreted on the basis of the surface structure of the PI particles, because a number of aromatic functionalities are in the chemical structure of the polymer chain backbone.
In this study, we reveal the suppression of non-specific hydrophobic interaction in poly(ethylene-co-glycidylmethacrylate) (PEGM) based spongy monolith (SPM), PEGM-SPM, which has recently be reported as a new platform of separation medium for affinity chromatography in our previous study, by an simple acidic treatment. Additionally, the immobilization procedures of protein-A toward the PEGM-SPM and the separation conditions for immunoglobulin G (IgG) were optimized for further effective affinity separations. As a result of treatment by a mixture of trifluoroacetic acid and acetonitrile, the hydrophobicity was dramatically suppressed in the PEGM-SPM. The optimizations for the density of PEGM in the PEGM-SPM, the protein A immobilization, and the binding/releasing conditions showed that variety of proteins and peptides were not retained on the protein A immobilized spongy column at all while IgG was absolutely separated by a simple stepwise pH gradient condition.
A solid-phase extraction-type collection device packed with Sunpak-H, styrene-divinylbenzene polymer particles, was used to identify 16 airborne polycyclic aromatic hydrocarbons (PAHs) using high-performance liquid chromatography (HPLC)-fluorescence detection and ultraviolet detector. The analytes were successfully collected with the collection device and quantitatively eluted using acetone as an elution solvent. The eluted PAHs were then separated by conventional HPLC and detected with a fluorescence or ultraviolet detector. The limit of detection of airborne PAHs was below 0.7 ng/m3 with an air sampling volume of 14,400 L. The relative standard deviations of the peak area were below 12%, and the method showed better repeatability than gas chromatographic analysis. The suitability of the method was confirmed by its application in identifying PAHs in tunnel and atmospheric air.
Herein, we report a method for the simultaneous derivatization and concentration of aspartic acid using an acidic polyacrylamide gel, fabricated in the microfluidic channel of a commercial poly(methyl methacrylate) (PMMA) microchip. This approach is based on a simple photochemical copolymerization for the fabrication of the anionic polyacrylamide gel. The intersection of the PMMA microchip was filled with a solution containing acrylamide, N,N'-methylene-bis-acrylamide, 2-acrylamidoglycolic acid, and riboflavin as photoinitiator, which functioned as a photocatalytic initiator. In situ polymerization near the cross of the sample outlet channel was performed by pinpoint irradiation with an argon ion laser beam, which is also used as the light source for fluorimetric detection. The electrokinetic properties, combined with the electrostatic repulsion between both sample and reagent components with the anionic groups in the polyacrylamide gel, enable simultaneous derivatization and entrapment at the cathodic side of the gel plug.
We examined the utility of LC-MS/MS/MS in the rapid quantitative analysis of clenbuterol in pig liver. Compared with LC-MS/MS in the SRM mode, which gave a chromatogram of pig liver containing interference peaks near the target component peak, LC-MS/MS/MS generated a clear chromatogram with no interference peaks. Validation of the method yielded favorable results for both LC-MS/MS in the SRM mode and LC-MS/MS/MS, with trueness values of 95.5% and 102%, repeatability of 1.9% and 5.5%, and within-laboratory reproducibility of 2.0% and 5.1%, respectively. Moreover, the recovery of clenbuterol-d9 used as surrogate was ≥70% in both measurement methods and thus, validation was achieved in terms of both selectivity and limit of quantification. The results suggest that LC-MS/MS/MS has highly selectivity for quantitative analysis as the influence of interference peaks is suppressed, and can be used when quantification is difficult with LC-MS/MS in the SRM mode due to matrix effects.
Photodegradation of sulindac (SL), which is clinically used as an anti-inflammatory, analgesic and antipyretic drug in an aqueous media under the ultraviolet (UV) irradiation was investigated. Degradation of SL and the generation of the photoproduct were monitored by means of high-performance liquid chromatography (HPLC). Residual amount of SL was decreased after UV-A, -B and -C irradiation with the generation of the photoproduct, but kinetics of degradation of SL and generation of the photoproduct seems to reach the equilibrium under only the UV-A irradiation. Based on the nuclear overhauser effect spectroscopy (NOESY) coupling pattern in nuclear magnetic resonance (NMR) spectrum and fragmentation pattern in electrospray ionization time-of-flight mass spectrometry (ESI-TOF/MS/MS), the photoproduct was identified as the trans-isomer of SL and the main pathway of SL photo-conversion was photoisomerization by the UV-A irradiation. Monitoring the degradation of SL and its photoproduct by the UV irradiation indicated that photochemical reaction of SL induced by the UV-A irradiation, which is photoisomerization, is different from that of induced by the UV-B or the UV-C irradiation, which is probably further degradation but there was no identification that a further photoproduct was generated from the initially formed photoproduct in the result of HPLC analysis. This is the first study showing the photoisomerization of SL induced by the UV irradiation in the aqueous media.
A new peak identification/quantification method, i.e., “shape-fitting” method, has been devised and applied to the determination of chiral amino acids in human plasma and urine. The shape fitting method enables the determination of target analytes using a part of the peak by mathematically predicting the whole peak even when the baseline is not clear. Using this method, D-glutamic acid (Glu) and D-proline (Pro) as well as their L-enantiomers in the plasma and urine were determined. The calibration lines of 4 target enantiomers were linear with correlation coefficients higher than 0.9998; the RSD values of the intra-day precision and inter-day precision were less than 6.70%. In the human plasma, trace amount of D-Pro (0.47 nmol/mL) was observed, and in the urine, 2.97 nmol/mL of D-Glu and 0.08 nmol/mL of D-Pro were successfully determined.
This paper describes simultaneous separation of six active ingredients, 6-ginger, 8-ginger, 10-ginger, 6-shogaol, honokiol, and magnolol, contained in ginger, processed ginger and magnolia bark by reversed-phase HPLC with core-shell (CS) type columns. Four different CS columns, Bipheny, Phenylhexyl, Cholester and typical C18 columns were employed. Among four CS columns, successful separation of these six components was achieved by a Biphenyl column within 5 min, using acetonitrile 50% mobile phase. The method was then applied for the assay of these active ingredients in Kampo products (extract granules), which are prepared according to the prescription using more than five crude drugs. 6-Gingerol and 6-shogaol were successfully separated from the other components in Kampo products, and a fast assay within 10 min was achieved in all four Kampo products tested. Two active ingredients contained in magnolia bark were also successfully separated and determined by the method in all four Kampo products tested within 10 min.
Nonaqueous capillary electrophoresis has the potential to separate water-insoluble analytes. Previously, we reported the separation of water-insoluble and neutral synthetic polymers in nonaqueous capillary zone electrophoresis using tetrahydrofuran (THF)-based ternary nonaqueous solutions. In this paper, the effect of the composition of a THF-based ternary solution (THF, acetonitrile, and methanol) containing cetyltrimethylammonium chloride (CTAC) on electrophoretic behavior is investigated using small organic compounds as prove analytes. In addition to general electrophoretic parameters such as electrophoretic mobility, analytical stability was also evaluated. The electric current, electrophoretic mobility of the benzyltriethylammonium cation (ion pair formation with chloride anion), and electrophoretic mobility of coronene (solvophobic interaction with the CTA cation) were dominated mainly by the THF content, and lower THF content resulted in higher values. In contrast, electroosmotic mobility was enhanced by an increase in THF content and was affected mainly by methanol content. Interestingly, in addition to stable electropherograms, we observed instable (fluctuation of baseline or zero current) electropherograms, which were obtained irregularly. Although a notable relation between the composition and the instable behavior was not observed, it is suggested that this “discontinuous instability” is related with the composition distribution (heterogeneous composition) of the ternary solvents in a capillary. Increasing the temperature effectively suppressed the composition distribution and has the potential to decrease the risk of instable behavior.