First, monodisperse OPA-QDs were obtained by purified with high-performance size exclusion chromatography (HPSEC) to remove excess OPA and aggregated QDs.

Secondly, excess free streptavidin (SA) in fresh prepared QD-labeled SA, and the monodisepese QD-SA were used in tumour maker determination.

Thirdly, monodisperse QD-labeled antibody bioprobes has been obtained by removing away the unbound antibody and suspended agglomerates of QDs at the same time via high-performance size exclusion chromatography (HPSEC).