Application of capillary isoelectric focusing with absorption imaging detection to the quantitative determination of human hemoglobin variants

The capillary isoelectric focusing (CIEF)-absorption imaging detector is a multicapillary separation instrument. Several protein samples can be separated and detected in a single run. The analysis time for one run is only 3 min. Because an imaging detector is used, the mobilization process of conventional CIEF is not necessary, eliminating such drawbacks as long analysis time and poor reproducibility in mobilization speed. Human hemoglobin variants were quantitatively determined using the instrument. The peak areas of the analytes were proportional to their concentrations in the concentration range of 0-200 micrograms/mL. Hemoglobin variant A2, which only comprises 2% of the whole hemoglobin, can be quantitatively determined with a standard deviation of less than 10%. For the high concentration variants, such as variant S, the deviation is less than 1%.