The present invention aims to provide a method for preparing
a peptide-containing sample that enables identifying a greater number of trace proteins in
proteome analysis of biological samples such as
dried blood spots (DBS), and that allows for the automated
processing of a large number of samples. By washing a
fiber aggregate having a biological sample adsorbed thereon with an aqueous
solvent, hydrophilic proteins contained in the biological sample are removed from the
fiber aggregate. Residual proteins bound to the
fiber aggregate are digested with a
protease, and the fiber aggregate is removed from the
digestion reaction mixture to obtain
a peptide mixture. By allowing magnetic particles such as
iron powder to be adhered to the fiber aggregate and magnetically adsorbing the fiber aggregate, operations such as
recovery, washing, and transfer of the fiber aggregate having the biological sample adsorbed thereon are carried out. The present invention also aims to provide a technique for easily and reliably separating non-magnetic
solid-phase carriers dispersed and suspended in a liquid from the liquid. By agitating a liquid containing magnetic particles and a non-magnetic
solid-phase carrier, the magnetic particles are allowed to be adhered to the non-magnetic
solid-phase carrier. The non-magnetic solid-phase carrier having the magnetic particles adhered thereto is then magnetically adsorbed and separated from the liquid. When a non-magnetic solid-phase carrier having a porous structure is used, magnetic particles can enter the voids within the porous structure through agitation, thereby allowing the non-magnetic solid-phase carrier to be more reliably magnetically adsorbed. When a
thickening agent is added to the liquid, the
sedimentation rates of the non-magnetic solid-phase carrier and the magnetic particles become equally small, allowing the two to mix well in the liquid and the magnetic particles to be uniformly incorporated into the non-magnetic solid phase carriers, thereby ensuring more reliable adsorption to the
magnet.