I ever obtained phloem sap from soybean  by centrifuging. You can try to isolate phloem sap from Arabidopsis at the mature stage using suitable centrifugation speed at RT. Of course, the plants should be cut by appropriate length, and then put them into the suitable tues, and stored at -80 ℃ for 30 min before centrifugation.

This video/protocol should be helpful: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3960974/

Also, look into Guelette et al. (2012): http://www.ncbi.nlm.nih.gov/pubmed/22442409

We've used this protocol for proteomics analysis of phloem sap collected from pathogen-infected Arabidopsis.

Very professional! Thank you!

EDTA is a reasonably good method of qualitative profiling of phloem metabolites, but it is also prone to contamination of from burst cells and xylem sap. The EDTA prevents the rapid occlusion of phloem sieve plates that normally occurs upon cutting, but the mechanism is unknown.  Normally the cutting should be done with the tissue already immersed in EDTA solution - that wasn't clear in the Arabidopsis video.  All this could be avoided by using a plant that spontaneously exudes phloem sap upon cutting and for which there is no occlusion to begin with.  The best choice is Lupinus (spp). I recommend Lupinus albus or Lupinus angustifolius (but other Lupinus species work too).  Ricinus works as well, but you must be careful with those infamous toxins.  For these plants you can just make a shallow stem incision (pod tips work very well too) and the phloem flows for several minutes and you can get mL amounts from a few mature plants. The collection is from a live, uncompromised plant, and reflects real-time physiology.

Thank you all for the informative comments!

I am working on Lac insect since 1997. I am also looking for a nano syringe which can used to drawing the sap from the phloem in field condition. My plan of work is to collect the sap and analyze it in lab for qualitative data