B–2
Model 3480 Electrospray Aerosol Generator
Figure B-1
Schematic Diagram of the Electrospray
C a p i l l a r y F l o w C h a r a c t e r i s t i c s
The liquid flow rate Q (nL/min) through the capillary is governed by
the following equation for Poiseuille flow in a circular tube:
⎟
⎠
⎞
⎜
⎝
⎛
Δ
⋅
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
⋅
⋅
⎟
⎠
⎞
⎜
⎝
⎛
⋅
⋅
=
L
P
D
c
Q
c
μ
π
8
1
2
4
Equation B-1
where:
D
c
is the capillary inner diameter (µm)
µ is the liquid viscosity (poise)
Δ
P is the pressure across the capillary (psi)
L is the length of the capillary (cm)
c is a constant to account for all unit conversions (4.14E4)
The capillary in the Electrospray has a diameter of 25
±
2 µm and a
length of 25 cm, a typical pressure across the capillary is 3.7 psi
(¼ atm), and the viscosity of water at 20
°
C is 0.89E-2 poise. Given
these conditions, the nominal liquid flow rate is 66 nL/min.
Table B-1 lists values of the liquid flow rate as a function of