Sl. Kaufman et al., MACROMOLECULE ANALYSIS BASED ON ELECTROPHORETIC MOBILITY IN AIR - GLOBULAR-PROTEINS, Analytical chemistry, 68(11), 1996, pp. 1895-1904
Globular proteins ranging in molecular mass from 5.7 to 669 kDa were s
eparated and analyzed using an aerosol technique based on the electrop
horetic mobility of singly-charged molecular ions in air. The ions wer
e produced by electrospraying and drying 100-nm-diameter droplets of a
Liquid suspension of the proteins, using ionized air to remove the dr
oplet charge due to the spray process. The electrophoretic mobility wa
s measured using a modified commercial continuous-flow differential mo
bility analyzer operated near atmospheric pressure. An unmodified comm
ercial condensation particle counter was used for detection. The conce
ntrations analyzed ranged from 0.02 to 200 mu g of protein/mL of buffe
r, with a liquid sample now rate of approximately 50 nL/min. Sampling
time of 3 min was used for each complete distribution measured. The el
ectrophoretic mobilities measured were determined entirely from air no
w rates, apparatus geometry, and applied potentials. Results were expr
essed as electrophoretic mobility equivalent diameters using a Millika
n formula.