Yinhan Gong

Application of diaza-18-crown-6-capped β-cyclodextrin bonded silica particles as chiral stationary phases for ultrahigh pressure capillary liquid chromatography

Two bonded chiral stationary phases (CSPs), 8-aminoquinoline-2-ylmethyl- and 8-aminoquinoline-7-ylmethyl-diaza-18-crown-6-capped [3-(2-O-beta-cyclodextrin)-2-hydroxypropoxy]propylsilyl silica particles (non-porous, 1.5 microm), have been prepared and evaluated using capillary liquid chromatography at high pressures (> or = 8000 p.s.i.). High column efficiency (up to 400 000 plates m(-1)) was achieved for chiral separations. These CSPs with two recognition sites, i.e. substituted-diaza-18-crown-6 and beta-cyclodextrin combined with high chromatographic efficiency provide good resolution of a variety of enantiomers and positional isomers in relatively short times under reversed-phase conditions. After inclusion of a Ni (II) ion from the mobile phase, the positively charged crown ether-capped beta-cyclodextrin facilitates specific static, dipolar, and host-guest complexation interactions with solutes.

Preparation and evaluation of calix[4]arene-capped β-cyclodextrin-bonded silica particles as chiral stationary phase for high-performance liquid chromatography

Calix[4]arene-capped [3-(2-O-beta-cyclodextrin)-2-hydroxypropoxy]propylsilyl-appended silica particles (C4CD-HPS), a new type of substituted beta-cyclodextrin-bonded chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC), have been synthesized by treatment of bromoacetate-substituted [3-(2-O-beta-cyclodextrin)-2-hydroxypropoxy]propylsilyl-appended silica particles (BACD-HPS) with calix[4]arene oxyanions in anhydrous N-methyl-2-pyrrolidone. The synthetic stationary phase is characterized by means of elemental analysis. This new type of CSP has a chiral selector with two recognition sites: calix[4]arene and beta-cyclodextrin (beta-CD). The chromatographic behavior of C4CD-HPS was studied with several disubstituted benzenes and some chiral drug compounds under reversed-phase conditions. The results show that C4CD-HPS has excellent selectivity for the separation of aromatic positional isomers and enantiomers of chiral compounds due to the cooperative functioning of calix[4]arenes and beta-CDs.

Androgenic and estrogenic response of green mussel extracts from Singapore's coastal environment using a human cell-based bioassay

In the last decade, evidence of endocrine disruption in biota exposed to environmental pollutants has raised serious concern. Human cell-based bioassays have been developed to evaluate induced androgenic and estrogenic activities of chemical compounds. However, bioassays have been sparsely applied to environmental samples. In this study we present data on sex hormone activities in the green mussel, Perna viridis, in Singapore’s coastal waters. P. viridis is a common bioindicator of marine contamination, and this study is a follow-up to an earlier investigation that reported the presence of sex hormone activities in seawater samples from Singapore’s coastal environment. Specimens were collected from eight locations around the Singapore coastline and analyzed for persistent organic pollutants (POPs) and heavy metals. Tissue extracts were then screened for activities on androgen receptors (ARs) and estrogen receptors (ER-α and ER-β) using a reporter gene bio-assay based on a HeLa human cell line. Mussel extracts alone did not exhibit AR activity, but in the presence of the reference androgenic hormone dihydrotestosterone (DHT), activities were up to 340% higher than those observed for DHT alone. Peak activities were observed in locations adjacent to industrial and shipping activities. Estrogenic activities of the mussel extract both alone and in the presence of reference hormone were positive. Correlations were statistically investigated between sex hormone activities, levels of pollutants in the mussel tissues, and various biological parameters (specimen size, sex ratio, lipid and moisture content). Significant correlations exist between AR activities, in the presence of DHT, and total concentration of POPs (r = 0.725, p < 0.05).

Synthesis of cyclam-capped β-cyclodextrin-bonded silica particles for use as chiral stationary phases in capillary electrochromatography

β-Cyclodextrin (β-CD) was anchored onto silica particles at its C(2) position, derivatized primarily at the C(6) position by treatment with bromoacetyl bromide, and finally reacted with two types of cyclams to form cyclam-capped β-CD-bonded silica particles. When used as chiral stationary phases in capillary electrochromatography, these novel bonded silica particles exhibited excellent enantioselectivities for chiral separations.

Enantiomeric separations in capillary electrochromatography with crown ether-capped β-cyclodextrin-bonded silica particles as chiral stationary phase

Two novel types of crown ether capped β-cyclodextrin (β-CD) bonded silica, namely, 4′-aminobenzo-X-crown-Y (X=15, 18 and Y=5, 6, resp.) capped [3-(2-O-β-cyclodextrin)-2-hydroxypropoxy] propylsilyl-appended silica, have been prepared and used as stationary phases in capillary electrochromatography (CEC) to separate chiral compounds. The two stationary phases have a chiral selector with two recognition sites: crown ether and β-CD. They exhibit excellent enantioselectivity in CEC for a wide range of compounds. After inclusion of metal ions (Na+ or K+) from the running buffer into the crown ether units, the stationary phases become positively charged and can provide extra electrostatic interaction with ionizable solutes and enhance the dipolar interaction with polar neutral solutes. This enhances the host-guest interaction with the solute and improves chiral recognition and enantioselectivity. Due to the cooperation of the anchored β-CD and the crown ether, this kind of crown ether capped β-CD bonded phase shows better enantioselectivity than either β-CD- or crown ether bonded phases only. These new types of stationary phases have good potential for fast chiral separation with CEC.

Preparation and characterization of 4-isopropylcalix[4]arene-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles as chiral stationary phase for high-performance liquid chromatography

A new type of 4-isopropylcalix[4]arene-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)propylsilyl-appended silica particles (IPC4CD-HPS) has been prepared by treatment of bromoacetate-substituted (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)propylsilyl-appended silica particles (BACD-HPS) with 4-isopropylcalix[4]arene oxyanions in anhydrous N-methyl-2-pyrrolidone. The bonded silica IPC4CD-HPS has been successfully used as chiral stationary phase (CSP) in high-performance liquid chromatography (HPLC) for the first time. The synthetic stationary phase was characterized by means of elemental analysis and Fourier transform infrared spectroscopy. This new CSP has a chiral selector with two anchored functional moieties: 4-isopropylcalix[4]arene and β-cyclodextrin. The chromatographic performance of IPC4CD-HPS was investigated by separation of positional isomers of several disubstituted benzenes and enantiomers of some chiral drug compounds under reversed-phase conditions. The results showed that IPC4CD-HPS had excellent selectivity for the separation of aromatic positional isomers and enantiomers of chiral compounds due to the cooperative functioning of the anchored 4-isopropylcalix[4]arenes and β-cyclodextrins.

Application of bromoacetate-substituted β-CD-bonded silica particles as chiral stationary phase for HPLC

Bromoacetate-substituted [3-(2-O-beta-cyclodextrin)-2-hydroxypropoxy]propylsilyl-appended silica particles (BACD-HPS), an important and useful synthetic intermediate for preparation of novel types of macrocycles-capped beta-CD-bonded silica particles including crown ether/cyclam/calix[4]arene-capped beta-CD-bonded silica particles, have been prepared and used as chiral stationary phase for HPLC. This synthetic stationary phase is characterized by means of elemental analysis. For the first time, the chromatographic behavior of BACD-HPS was systematically evaluated with several disubstituted benzenes and some chiral drug compounds under both normal and RP conditions in HPLC. The results show that BACD-HPS has excellent selectivity for the separation of aromatic positional isomers and chiral isomers of some drug compounds when used as stationary phase in HPLC.

Preparation and application of rifamycin-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles as chiral stationary phase for high-performance liquid chromatography

Rifamycin-capped (3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles (RCD-HPS), a new type of substituted β-cyclodextrin-bonded chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC), have been synthesized by the treatment of bromoacetate-substituted-(3-(2-O-β-cyclodextrin)-2-hydroxypropoxy)-propylsilyl-appended silica particles (BACD-HPS) with rifamycin SV in anhydrous acetonitrile. The stationary phase is characterized by means of elemental analysis and Fourier-transform infrared spectroscopy. This new CSP has a chiral selector with two recognition sites: rifamycin and β-cyclodextrin (β-CD). The chromatographic behavior of RCD-HPS was studied with several disubstituted benzenes and some chiral drug compounds under reversed-phase HPLC mobile phase conditions. The results show that RCD-HPS has excellent selectivity for the separation of aromatic positional isomers and enantiomers of chiral compounds due to the cooperative functioning of rifamycin and β-CD.

PREPARATION AND APPLICATION OF MIXED OCTADECYLSILYL- AND (3-(C-METHYLCALIX[4]RESORCINARENE)-HYDROXYPROPOXY)-PROPYLSILYL–APPENDED SILICA PARTICLES AS STATIONARY PHASE FOR HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

A new type of mixed octadecylsily (ODS)- and (3-(C-methylcalix[4]resorcinarene)-2-hydroxypropoxy)-propylsilyl–appended silica particles (ODS-MCR-HPS) have been prepared and used as stationary phase for high-performance liquid chromatography (HPLC) for the first time. Elemental analysis and Fourier-transform infrared spectroscopy have been applied to characterize the synthetic ODS-MCR-HPS. The new stationary phase contains two types of interaction sites for separation: ODS and MCR. The chromatographic performance of ODS-MCR-HPS was investigated by separating several disubstituted benzenes and some aromatic hydocarbons under both reversed-phase and normal-phase conditions. The results show that ODS-MCR-HPS exhibits excellent selectivity for the separation of positional isomers of disubstituted benzenes and mixtures of some aromatic hydrocarbon compounds due to the cooperative and complementary functioning of the ODS and MCR under different mobile phase conditions.

Preparation and Application of Aza-15-crown-5-capped Methylcalix[4]resorcinarene-Bonded Silica Particles for Use as Chiral Stationary Phase in HPLC

Aza-15-crown-5-capped (3-(C-methylcalix[4]resorcinarene)-2-hydroxypropoxy)-propylsilyl (MCR-HP)-appended silica particles (15C5-MCR-HPS), a new type of substituted C-methylcalix[4]resorcinarene (MCR)-bonded chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC), have been synthesized by reaction of bromoacetate-substituted MCR-HPS with excessive aza-15-crown-5 in anhydrous acetonitrile in the presence of potassium carbonate. The bonded phase 15C5-MCR-HPS is characterized by elemental analysis and further evaluated by separating several disubstituted benzenes and some chiral drug compounds in HPLC. The new CSP has a chiral selector with two recognition sites: 15-crown-5 and MCR-HP, which can provide cooperative multiple interactions with solutes to enhance chiral recognition and to improve chromatographic separation. The chromatographic evaluation results show that 15C5-MCR-HPS has excellent selectivity for the separation of aromatic positional isomers and enantiomers of some chiral compounds under multiple-mode mobile phase conditions including normal phase, reversed phase, and polar organic mobile phase conditions.Graphical abstract