A method and apparatus for concentrating dilute biomolecules in samples using electrophoresis are described. The method involves using the charged nature of the biomolecules to localize them to a microspot containing a dialysis membrane. The method and apparatus may also be used for identifying the presence of a biomolecule in a mixture or to quantitate the amount of a specific biomolecule in a mixture. The method and apparatus may also be used to produce a high throughput method for analysis and quantitation of a sample containing biomolecules.