Biomedical subjects

Qilong Ren

Publications and source records attributed to Qilong Ren.

7 recordsLinked to original sources

PubMed2006

Determination of soyasaponins Ba and Bb in human serum by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

A rapid, sensitive and selective high-performance liquid chromatography-tandem mass spectrometric method (HPLC-MS-MS) has been developed and validated for the determination of soyasaponins Ba and Bb in human serum using glycyrrhizin as internal standard (I.S.). Soyasaponins Ba and Bb were extracted from human serum by liquid-liquid extraction and cleaned up by C(18) solid-phase extraction (SPE), followed by separation on a C(18) reversed-phase column using acetonitrile/water containing 0.025% acetic acid as a mobile phase for gradient elution. Soyasaponins Ba and Bb, and I.S. were ionized by negative ion pneumatically assisted electrospray and detected by HPLC-MS-MS in the multiple-reaction monitoring (MRM) mode using precursor-->product ion combinations at m/z 958-->940, 942-->924 and 822-->351, respectively. The calibration curves were linear (r(2)>0.991) in the concentration range of 0.5-100.0 ng/mL, with lower limits of quantification of 0.5 and 0.3 ng/mL for soyasaponins Ba and Bb, respectively, in human serum. Intra-day and inter-day relative standard deviations (R.S.D.) were less than 7.9 and 11.3%, respectively. The mean recoveries of soyasaponins Ba and Bb ranged from 92 to 101% and from 85 to 94%, respectively.

Chromatography, High Pressure Liquid↗

PubMed2006

Parallel pore and surface diffusion of levulinic acid in basic polymeric adsorbents.

The equilibrium and kinetics of levulinic acid (LA) adsorption on two basic polymeric adsorbents, 335 (highly porous gel) and D315 (macroreticular), were investigated. Experimental adsorption rates in batch stirred vessels under a variety of operating conditions were described successfully by the parallel pore and surface diffusion model taking into account external mass transfer and nonlinear Toth isotherm. The film-pore diffusion model was matched with the rate data and the resulting apparent pore diffusivities were strongly concentration-dependent and approached to a constant value for 335 adsorbent. Thus, the constant value was taken as the accurate pore diffusivity, while the pore diffusivity in D315 was estimated from the particle porosity. The surface diffusivities decreased with increasing initial bulk concentration for both adsorbents. The inverse concentration dependence was correlated reasonably well to the change of isosteric heat of adsorption as amount adsorbed.

Adsorption↗

PubMed2006

Rapid quantification and characterization of soyasaponins by high-performance liquid chromatography coupled with electrospray mass spectrometry.

A method using high-performance liquid chromatography (HPLC) with electrospray ionization mass spectrometry (ESI-MS) in the negative mode is presented for the quantification and characterization of different soyasaponins using six authentic soyasaponin standards. This method was successfully applied to the rapid separation of diverse soyasaponins, more than 50, including soyasaponins A in different degrees of acetylation, and soyasaponins B in both their 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP)-conjugated and non-conjugated forms in different samples in one single run for only 30 min. Standard calibration curve was linear over the concentration range of 0.010-1.0 mg/L for each soyasaponin. Within-day and day-to-day relative standard deviations were less than 9.2 and 13.1%, respectively.

Acetylation↗

PubMed2005

Separation of naproxen enantiomers by supercritical/subcritical fluid chromatography.

An isocratic supercritical/subcritical fluid chromatography method for the separation of naproxen enantiomers on the Kromasil CHI-TBB column was investigated. The mobile phase was composed of supercritical CO2 with 2-propanol as modifier. The experimental conditions were temperature 293 K-323 K, pressure 9.4 MPa-21.3 MPa, and 2-propanol concentration 6%-15% (by mass), respectively. The enthalpic contribution to the overall enantiomer transfer energy was more important than the entropic contribution in the temperature range examined. The preferred operation conditions were 293 K, 9.4 MPa, and the concentration of 2-propanol in the mobile phase 11% (by mass).

2-Propanol↗

PubMed2005

[Progress in the determination of trace polycyclic aromatic hydrocarbons in complex matrices].

The analytical methods of polycyclic aromatic hydrocarbons (PAHs) in different samples, e.g., vegetable oils, waters and soils, have been reviewed. The sample pretreatment steps play a key role during the analysis due to the very low PAHs contents. The pretreatment methods for water samples include liquid-liquid extraction, solid phase extraction, etc. The pretreatment methods for soil samples include Soxhlet extraction, ultrasonic extraction, microwave assisted extraction, accelerated solvent extraction, and supercritical fluid extraction, etc. The pretreatment methods for vegetable oils include saponification, liquid-liquid partitioning, caffeine complexation, solid phase extraction, and supercritical fluid extraction, etc. Gas chromatography with mass spectrometry and high performance liquid chromatography (HPLC) with fluorescence detection are mainly used for separation and detection. The novel on-line determination method, e.g., the coupling of liquid chromatography with high performance liquid chromatography, or with gas chromatography may obtain ideal results. Fifty-two references are cited.

Chromatography, Gas↗

PubMed2004

[Extra-thermodynamic properties of 2-arylpropionic acids on a chiral-AGP column by high performance liquid chromatography].

The effect of temperature (274-313 K) on the chromatographic behavior of naproxen and ibuprofen on a Chiral-AGP column was investigated with a mobile phase consisting of 50 mmol/L phosphate buffer (pH 6.41) and 0.5% (or 1.0%, v/v) 1-propanol. Higher temperature was found disadvantageous to the enantiomeric separation. With temperature increased, the retention time, resolution and selectivity of the chiral separation were decreased. The resolution of naproxen was larger than that of ibuprofen in all cases. When naproxen and ibuprofen enantiomers were entirely separated by the mobile phase containing 1.0% 1-propanol, the maximum temperatures allowed were 298 K and 288 K, respectively. All of the Van' t Hoff plots of the In k vsrsus 1/T were found to have good linearity, with the correlation coefficients better than 0.99 in all cases. The thermodynamic parameters (changes of enthalpy, i. e., deltaH0, for the transfer of enantiomers from the mobile phase to the stationary phase and differences of enthalpy and entropy changes, i. e., deltaS,R deltaH0 and deltaS,R deltaS0) were calculated. In general, in the temperature range examined the enthalpic contribution to the overall enantiomer transfer energy was found to be more significant than the entropic one.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2003

Study on retention factor and resolution of tocopherols by supercritical fluid chromatography.

To develop a process for separation of natural alpha-tocopherol from gamma- and delta-tocopherols by supercritical fluid chromatography, the effects of pressure, temperature and the ethanol concentration in the mobile phase on the retention factor and resolution of tocopherols were studied comprehensively. The ranges of the studied pressure, temperature and ethanol concentration were 12 to 20 MPa, 30 to 90 degrees C and 0 to 6.54 wt% respectively. It was found that the retention factors of the tocopherols decrease as the ethanol concentration in the mobile phase increases. The resolution of tocopherols increases as the temperature increases and as the pressure decreases, and there is a maximum of the ethanol concentration curve at a definite temperature and pressure. A simplified model of the retention factor ln k' = A + B/T + C rho - D(rho/T) + E(rho2/T) based on the unified molecular theory was proposed. The experimental data were correlated by the model with the AARD% less than 14.70%.

Chromatography, Supercritical Fluid↗