Development and application of chip-based and capillary-based capillary electrophoresis : inductively coupled plasma atomic emission spectroscopy and mass spectrometry
Abstract of thesis entitled
DEVELOPMENT AND APPLICATION OF CHIP-BASED AND
CAPILLARY-BASED CAPILLARY ELECTROPHORESIS -
INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION
SPECTROSCOPY AND MASS SPECTROMETRY
for the degree of Doctor of Philosophy
at The University of Hong Kong
in July 2005
A novel interface has been developed to couple chip-based capillary electrophoresis (CE) to inductively coupled plasma (ICP) for metal species separation and quantification. The CE-ICP interface was based on- cross-flow nebulization. The nebulization efficiency of the interface and broadening effects of the spray chamber / aerosol transfer tube have been characterized. A novel scheme of manipulation of sample and buffer solution flow in the microchannel of the CE chip has also been developed. Two capillaries were inserted into the polydimethylsiloxane (PDMS) microchip for solution injection. The direction and flow rate of the solution were controlled independently using two micro-syringe pumps. The capillary -microchannel connection requires precise alignment of the capillary outlets (internal diameter 50 um and external diameter 320 um) and the 50-um microchannel. A novel method to pre-fabricate a set of holes in the PDMS slab for precise capillary-microchannel alignment has been developed.
To allow flexible and rapid prototyping of the PDMS chips, a new PDMS polymer curing method using IR lamp heating and a new plasma treatment method
of the PDMS slabs using microwave-oven-generated plasma have been developed. The microwave plasma-treated PDMS slabs sealed irreversibly to form microfluidic devices that could sustain a solution flow under an applied pressure of 42 psi without leakage. The topology and relative concentration of surface oxygen-containing functional groups of the plasma-treated PDMS surface were characterized using atomic force microscopy (AFM) and attenuated total reflection-Fourier Transform infrared spectroscopy (ATR-FTIR). The microwave plasma-treated PDMS surface was found to bear silica characteristics.
A new continuous-flow field amplified sample stacking (FASS) preconcentration method has been developed. A 3-mm water plug was introduced into the microchannel of the CE chip to set up a concentration gradient at the boundaries of buffer solution-water plug and sample solution-water plug. Continuous flow of sample solution in the microchannel replenished analyte ions during FASS preconcentration of the analyte. Large quantities of analyte ions could be preconcentrated into the "water" plug. Enhancement in analyte concentration of 100 fold or higher was achieved. Calibration curves of linearity of at least one order of magnitude of analyte concentration were obtained using the preconcentration method.
Capillary-based CE-ICPAES or ICPMS were used to characterize metal species in the extract and fluid of plant samples. The feasibility of sample preparation methods including microwave-assisted extraction and ultrasonic extraction in water or mixed solvents was examined.
School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:capillary electrophoresis inductively coupled plasma atomic emission spectrometry
Date of Publication:01/01/2005