Method for transferring one or more portions of fluid from a specimen tube, comprising: providing an elongate connector comprising an elongated tube having a lumen or through-hole extending between proximal and distal ends thereof, a Luer-compatible female taper provided on the proximal end of the connector, a flange provided proximate the distal end of the connector; providing a tube seal mounted on the distal end of the connector, the tube seal comprising an elastomeric member having a longitudinal axis, a proximal end, a distal end, and a through-hole extending therebetween, the distal end having a frustoconical or chamfered face forming a funnel, the elastomeric member having an outer diameter sized to sealingly engage with an inner surface of the specimen tube; advancing the distal end of the connector and the tube seal into the specimen tube, the funnel directing the first layer into the through-hole of the connector.