Nian Wu

Chiral separations using dextran and bovine serum albumin as run buffer additives in affinity capillary electrophoresis

Abstract A method utilizing dextran as a run buffer additive in addition to bovine serum albumin (BSA) for chiral separation by means of affinity capillary elec

Peroxyoxalate chemiluminescence detection in capillary electrophoresis

Abstract The feasibility of employing peroxyoxalate chemiluminescence (PO-CL) detection in capillary electrophoresis (CE) was demonstrated using a two- step approach for the CE separation and dynamic elution (elution under pressure) of the analytes. In this approach, potential problems associated with incompatibilities between mixed aqueous-organic solvent and clectrically driven separation systems were avoided by switching off the CE power supply at an appropriate time and connecting the CE capilliary to a syringe pump to effect dynamic elution. The effect of dynamic flow- rate and PO-CL reagent concentration on the CL signal intensity and/or peak width were examined for the measurements of three dansylated amino acids. The average limit of detection for these analytes using this PO-CL method is about 1.2 fmol ( ca. 85 nM) which is approximately 35-fold lower than UV absorption methods.

Speciation of aluminum using capillary zone electrophoresis with indirect UV detection

Abstract Capillary zone electrophoresis was evaluated as a method for the speciation of aluminum in aqueous solution using indirect UV absorption detection. Flu

Enantiomeric Separation by Cyclodextrin-Modified Micellar Electrokinetic Chromatography Using Bile Salt

Abstract A method for enantiomeric separation by cyclodextrin-modified micellar electrokinetic chromatography (MEKC) with bile salt micelles is described. The enantiomeric resolution was achieved with a mixed sodium taurodeoxycholate (TDC)-β-cyclodextrin (CD) solution (pH 7–9) utilizing a bare capillary. In sodium dodecyl sulfate (SDS)-CD solutions, similar result were not obtained. The effect of varying concentrations of TCD and β-CD and pH on the selectivity and resolution were also briefly investigated.

Separation of porphyrins and porphyrin isomers in capillary electrophoresis using mixed ionic surfactant-bovine serum albumin buffer systems

Abstract The separation of six porphyrins having two to eight carboxylic acid side-chains by capillary electrophoresis using a combination of ionic surfactant and protein as a novel modifier in the run buffer is reported. Using sodium dodecyl sulfate (SDS) together with bovine serum albumin (BSA) as buffer additives, efficient and reproducible separation of mesoporphyrin, coproporphyrin, uroporphyrin, penta-, hexa- and heptacarboxylporphyrins was achieved at pH 7.4 whereas sodium taurodeoxycholate (bile salt) combined with BSA in the run buffer separated type I and III isomers of coproporphyrin as well. The presence of SDS or bile salt appeared to minimize protein-and/or porphyrins-inner capillary wall (untreated silica) interaction and to enhance solubilization and selectivity of porphyrins due to the formation of ionic surfactant-protein complex(es) in the run buffer.

Light emission from bilirubin using the peroxyoxalate chemiluminescence reaction

Abstract The observation of light emission from bilirubin in an organic solvent as a result of the peroxyoxalate chemiluminescence reaction is reported for the first time. The results presented herein indicate that bilirubin chemiluminescence can be detected in N,N′ dimethylformamide but not in chloroform, dimethylsulfoxide, or pyridine. To elucidate this phenomenon, the effects of solvent on the chemiluminescence intensity were examined as a function of solvent composition. Furthermore, analytical utilization of the present observation for the determination of bilirubin in biological materials was evaluated. Relative and absolute limits of detection were found to be 8.5 nmol 1 −1 and 5.0 ng, respectively, and the response was found to be linear at least over three orders of magnitude. Selectivity for the detection of bilirubin in the presence of a number of common interference species was also examined. Finally, the visible spectrum of bovine serum in the blue-green region was obtained using the present chemiluminescence method and was briefly compared with those obtained from absorption ad fluorescence methods.

Separation of serum bilirubin species by micellar electrokinetic chromatography with direct sample injection

Four major bilirubin species in serum were separated by micellar electrokinetic chromatography with 25 mM sodium dodecyl sulfate (SDS) and 20 mM sodium tetraborate-boric acid buffer at pH 8.5. Due to the solubilization of the serum proteins by the SDS micelles, serum samples were injected directly into a 50 cm x 75 microns I.D. fused-silica capillary and complete separation of the four bilirubin species was accomplished within ca. 10 min without extensive sample pretreatment. Detection was performed by absorbance at 450 nm and average limit of detection was in the 6.0 microM concentration range. The usefulness of this method was demonstrated for the separation and detection of a number of bilirubin species present in pathological human serum samples.

Investigations of gas-flow patterns within a cylindrical glass tube having dimensions identical with those of a graphite furnace atomizer under the influence of forced convective flow

Gas-flow patterns within a cylindrical glass tube having the same dimensions as a typical graphite furnace atomizer were investigated by introducing two streams of argon gas seeded with a light-scattering medium of TiO2 particles into the open ends of the tube and viewing the scattering profiles of the particles. By placing a sample of iodine solution near the centre or ends of the cylindrical glass tube, further insight into gas-flow patterns is gained by examining the spatial distributions of the iodine vapour under the influence of convective flow. The TiO2 particle and iodine spatial profiles suggest that at room temperature the argon streams follow a laminar-flow pattern in the bulk-flow region between the ends of the cylindrical tube and the sample introduction hole; however, at the junction region where the two argon streams converge and discharge from the dosing hole, local turbulences or eddies may be generated owing to abrupt changes in gas-flow velocity and direction in the vicinity of an area (boundary layer) directly beneath the dosing hole.

Improved Detection System for Whole Column Detection in Capillary Isoelectric Focusing

Abstract An improved whole capillary scanning device was constructed which permitted die scanning of capillaries. This device allowed examination of electropherograms during the course of development, as well as eliminated the need to handle the capillaries after separation. The scanning device consisted of a detector constructed around the capillary, which was laterally driven by a DC motor via a rubber belt along polished steel rail. This design produced noise levels better than die earlier prototype on a separation of test proteins. The S/N ratio is close to that of static detection, provided a bare fused silica capillars is scanned. UV transparent capillaries still produced unacceptable noise levels, probably due to optical inhomogeneities in the outer coating which exaggerated minor positional changes due to vibration.

The Effect of Fumed Silica Suspensions on the Peroxyoxalate Chemiluminescence of Biological Porphyrins

Abstract An investigation of the effect of fumed silica suspensions on the chemiluminescence of various biological porphyrins was carried out. The effect of silica particle size, concentration, solvents and pH was investigated for a variety of some common biological porphyrins; hematoporphyrin and coproporphyrin. Both the DNPO (di-nitrophenyl oxalate) and TCPO (tri-chlorophenyl oxalate) systems were used and compared. Enhancement of the chemiluminescence signal was observed for both hematoporphyrin and coproporphyrin. A similar effect for uroporphyrin was not observed. The uniformity of the silica suspensions was also briefly investigated over a few different particle sizes. All of these effects were observed for two different container types; i.e., both square and round cuvettes. ∗ Current address: Department of Chemistry, University of Illinois at Champaign-Urbana, Urbana, IL 61801