Investigation of effective biomarkers for cancers is currently a popular area of study in clinical and cancer researches, because it can potentially lead to pre-cancer screening or pre-cancer diagnosis and may provide useful information on cancer type and the disease's stage of progression. More and more biochemical or chemical fluid components of the human body such as urine, blood, and cerebrospinal fluid have been considered to contain biomarkers, which are useful in cancer researches, pre-cancer diagnosis, and cancer follow-ups during or after cancer treatment. Several modern analytical techniques, such as gas chromatography (GC), high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and other separation techniques as well as hyphenated techniques, have been extensively used in study of cancer biomarkers. Among these techniques, CE is considered to be a highly efficient and practical analytical technique because of the small sample volume requirement and its wide separation versatility, ranging from small inorganic molecules to large biomolecules. This review discusses the latest developments involving biomarkers and their analysis by CE, including a discussion of instrumental conditions, method developments, and data analysis.

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A method to detect polyamines and catecholamines in PC-12 tumor cell extracts by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) is described for the first time. Both derivatization conditions and buffer concentrations and pH were optimized. Under optimized conditions the polyamines (putresine, spermine, spermidine) and catecholamines (dopamine, norepinephrine, epinephrine, serotonin) were derivatized with fluorescein isothiocyanate and separated at 25 kV in a fused-silica capillary (50 microm ID x 40 cm) with 0.1 M borate, pH 9.0, in less than 18 min. The influence of running buffer conditions, such as buffer pH and concentrations, were also investigated. Linearity of the analytes ranged from 0.05 to 1.0 micromol/L, and the detection limit (S/N = 3 ) ranged from 0.03 to 2.50 nmol/L. The concentrations of polyamines and catecholamines in PC-12 tumor cell extracts were determined with this method.

The on-line incorporation of cloud point extraction (CPE) to flow injection analysis (FIA) is demonstrated for the first time. The technical difficulties of inducing the cloud point phenomenon, separating the surfactant-rich phase from the aqueous phase, and detecting trace amounts of analyte(s) in the presence of the highly scattering surfactant medium in an on-line FIA system were resolved by the following: (1) mixing the sample solution containing the analyte(s) and CPE surfactant with an appropriate salting-out agent, (2) using a collection column to entrap the analyte-containing surfactant aggregates, and (3) employing the peroxyoxalate chemiluminescence reaction for the sensitive and selective determination of the analyte(s) in the presence of surfactant micelles. The figures of merit for the determination of coproporphyrin in pretreated urine samples were as follows: precision, 1.1-2.2% (RSD); limit of detection, 2.0 microg/L; and the calibration curve was linear from 46 to 2319 (micro/L (r = 0.9996).