Is it possible detach one single molecule of water into vacuum lab?
One can certainly separate water molecules at low temperature on a surface, as demonstrated by STM images. In Hossain et al. 2003 they show that the molecules stick to C defects on the surface. In (Shin et al 2010) they have nicer pictures of dissociated molecules on the surface.
I suspect one can also make free-flying vacuum molecules simply by having heated water evaporate in vacuum and sending the thin vapor through filters and turbomolecular pumps in the right direction. It is easier to capture and control a charged object, but I see no technical reason why one could not get a single molecule. One might also use optical tweezers to bring togeher a $H^+$ and a $OH^-$ and build on from scratch.
Hossain, M. Z., Yamashita, Y., Mukai, K., & Yoshinobu, J. (2003). Model for C defect on Si (100): The dissociative adsorption of a single water molecule on two adjacent dimers. Physical Review B, 67(15), 153307.
Shin, H.-J., Jung, J., Motobayashi, K., Yanagisawa, S., Morikawa, Y., Kim, Y., & Kawai, M. (2010). State-selective dissociation of a single water molecule on an ultrathin MgO film. Nature Materials, 9(5), 442–447. doi:10.1038/nmat2740