A syringe works well. Use thin plastic extender tubing and/or glass capillary tubes to reach the aqueous layer. If working with larger volumes, just tap off a small volume, measure, then pour back in. Its all about relative mechanical loss...
TIP - when lowering the syringe through the NP towards the aqueous, it will 'swallow' some NP up the tip. To overcome this, draw up the syringe a little before lowering so that when it is in the aqueous, you can squeeze the syringe to clear it. Then suck up the aqueous.