Using a regulated pipette dropper, a droplet of blood serum can be hung at the tip for a period of time long enough for PIXE analysis in air. The external proton beam of the University of Delaware proton microprobe was used to bombard the droplet in room atmosphere. Since no sample preparation is needed, the sample was analyzed in five to ten minutes when only the relative concentrations were needed. To obtain absolute concentration, known concentration of a certain element has to be mixed in the serum to be used as a normalizing factor. This is necessary because charge collection in room atmosphere is not reliable, and no PIXE detectable element in serum is known to be constant enough in concentration that can serve this purpose of normalization. NH 4Br has been tried and found to be very suitable and satisfactory for this purpose.