Biomedical subjects

Lingxin Chen

Publications and source records attributed to Lingxin Chen.

6 recordsLinked to original sources

PubMed2006

Off-line comprehensive two-dimensional high-performance liquid chromatography system with size exclusion column and reverse phase column for separation of complex traditional Chinese medicine Qingkailing injection.

A comprehensive two-dimensional liquid chromatography system was constructed on the combination of size exclusion chromatography (SEC) and reverse phase liquid chromatography (RPLC). The first dimension used a SEC column with 300 mm x 8mm i.d., packed with Toyopearl HW-40S. The column was eluted with 0.05 mol/l Tris-HCl (pH 6.9) at a flow rate of 0.4 ml/min. The second dimension used a RPLC column with 100 mm x 4.6mm i.d., which was operated in gradient form at a flow rate of 1.0 ml/min. An automatic switching valve was used to collect the effluent of the SEC column every 3 min, and the effluent was automatically injected into the RPLC column. Mass spectrometer was used for peak identification. This system was used to separate Qingkailing injection, a traditional Chinese medicine (TCM). The result showed that the total peak capacity of this system could reach 1134 and the qualitative analysis of seven chemical components of the Qingkailing injection was accomplished by this system. The results show that comprehensive two-dimensional liquid chromatography system is of great importance and high value in the separation of complex TCM.

Chromatography, High Pressure Liquid↗

PubMed2005

A microfluidic device using a green organic light emitting diode as an integrated excitation source.

A simply fabricated microfluidic device using a green organic light emitting diode (OLED) and thin film interference filter as integrated excitation source is presented and applied to fluorescence detection of proteins. A layer-by-layer compact system consisting of glass/PDMS microchip, pinhole, excitation filter and OLED is designed and equipped with a coaxial optical fiber and for fluorescence detection a 300 microm thick excitation filter is employed for eliminating nearly 80% of the unwanted light emitted by OLEDs which has overlaped with the fluorescence spectrum of the dyes. The distance between OLED illuminant and microchannels is limited to approximately 1 mm for sensitive detection. The achieved fluorescence signal of 300 microM Rhodamine 6G is about 13 times as high as that without the excitation filter and 3.5 times the result of a perpendicular detection structure. This system has been used for fluorescence detection of Rhodamine 6G, Alexa 532 and BSA conjugates in 4% linear polyacrymide (LPA) buffer (in 1 x TBE, pH 8.3) and 1.4 fmol and 35 fmol mass detection limits at 0.7 nl injection volume for Alexa and Rhodamine dye have been obtained, respectively.

Acrylic Resins↗

PubMed2005

Application of a high-pressure electro-osmotic pump using nanometer silica in capillary liquid chromatography.

A novel designed electro-osmotic pump (EOP) with simple structure was assembled using three 20 cm x 530 microm i.d. fused-silica capillaries packed with 20 +/- 5 nm silica grains for capillary liquid chromatography. It was found that the pump could generate pressures over 20 MPa and several microL/min flow rate for most of the liquids being delivered with the applied voltage less than 10 kV. By increasing the pressure, decreasing the applied voltage and the electrical current, the thermodynamic efficiency was about 1-4%. A practical application of the EOP in a 20cm x 150 microm i.d. 3 microm C18 fused-silica analytical capillary column demonstrated the applicability of the pump.

Chromatography, Liquid↗

PubMed2004

Preparation and characterization of long methacrylate monolithic column for capillary liquid chromatography.

Long methacrylate monolithic columns (100 cm x 320 microm i.d.) were prepared from silanized fused-silica capillaries of 320 microm i.d. by in situ copolymerization of butyl methacrylate (BMA) with ethylene dimethacrylate (EDMA) in the presence of a suitable porogen. The separation performance and selectivity of the column were evaluated and compared with a 25 cm x 320 microm i.d. column prepared in the same way by capillary high-performance liquid chromatography (micro-HPLC). The results showed that the 1 m long monolithic column can generate 33 x 10(3) plate number and exhibited good permeability, higher sample loadability, and separation capability.

Chromatography, High Pressure Liquid↗

PubMed2004

Study on conical columns with different conical angles for semi-preparative liquid chromatography.

The dynamic flow profiles and separation performances in conically shaped preparative liquid chromatographic columns (inlet i.d. larger than outlet i.d.) with three different angles (7, 10 and 15) were studied and compared with cylindrical column of the same length and internal volume. The shapes of dynamic flow profiles were studied by on-column visualization method. The transparent chromatographic columns made of polymethyl methacrylate (PMMA), packed with C18 bonded silica, were immerged into a cubic pool filled with glycerol to eliminate the cylindrical and conical lens effect. The flow profiles of colored iodine solution in the columns were observed clearly using cyclohexane as mobile phase since the refractive indices of C18, column wall and the mobile phase are very close. In the conical column of 15 degrees (20-7 mm i.d.) the mobile phase in the central region migrated slower than in wall region as it moved toward the column outlet, while in the conical column of 7 degrees (17-11 mm i.d.) the mobile phase in the central region migrated faster than in wall region just like in cylindrical column. We found that a plug-like flow profile was generated in the conical column of 10 degrees (18-9 mm i.d.) during the whole migration process. A carmine and brilliant blue mixture was used as a probe to test the separation ability of the columns. The resolutions of the two compounds on the conical column of 7, 10, 15 and on the cylindrical column were 0.6, 1.57, 1.29 and 0.8, respectively.

Benzenesulfonates↗

PubMed2004

Study of an electroosmotic pump for liquid delivery and its application in capillary column liquid chromatography.

A packed-bed electroosmotic pump (EOP) was constructed and evaluated. The EOP consisted of three capillary columns packed in parallel, a gas-releasing device, Pt electrodes and a high-voltage power supply. The EOP could generate output pressure above 5.0 MPa and constant flow rate in the range of nl/min to a few microl/min for pure water, pure methanol, 2 mM potassium dihydrogenphosphate buffer, the buffer-methanol mixture and the pure water-methanol mixture at applied potentials less than 20 kV. The composition of solvent before/after pumping was quantitatively determined by using a gas chromatograph equipped with both flame ionization detector and thermal conductivity detector. It was found that there were no apparent changes in composition and relative concentrations after pumping process for a methanol-ethanol-acetonitrile mixture and a methanol-water mixture. Theoretical aspect of the EOP was discussed in detail. An capillary HPLC system consisting of the EOP, an injection valve, a 15 cm x 320 microm i.d., 5 microm Spherigel C18 stainless steel analytical column, and an on-column UV detector was connected to evaluate the performance of the EOP. A comparative study was also carried out with a mechanical capillary HPLC pump on the same system. The results demonstrated that the reproducibility of flow rate and the pulsation-free flow property of the EOP are superior to that of mechanical pump in capillary HPLC application.

Acetonitriles↗