TSI Incorporated 3480, Руководство пользователя

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Operating the Electrospray 4–3
range of conductivities, a 0.2 S/m buffer solution is typically used.
An experimental analysis of the useful range of liquid conductivity
as a function of liquid flow rate using an electrospray method is
discussed in the following journal article:
Chen, Da-Ren, David Y.H. Pui, and Stanley L. Kaufman [1995]
“Electrospraying of Conducting Liquids for Monodisperse Aerosol
Generation in the 4 nm to 1.8 µm Diameter Range.”
J. Aerosol Sci., 26:963-977.
Measuring and Adjusting pH
A pH meter is useful for measuring the pH of a buffer solution.
Ammonium hydroxide or acetic acid can be added to the buffer
solution to increase or decrease the pH value, respectively. Since
the pH value should be greater than the pI value for proteins, a
useful reference for pI values of selected proteins is:
Righetti, P.G., G. Tudor, and K. Ek [1981]
“Isoelectric Points and Molecular Weights of Proteins: A New Table.”
Chromatographic Reviews 149,
J. Chromatography, 220:115-194.
Typical Solutes
Any solid or nonvolatile liquid that is soluble in a buffer solution
can be used to make a sample for use with the Electrospray. With a
standard buffer solution, useful solutes include sucrose, PSL, and
proteins. The properties of each solute and methods of preparing
each sample are discussed below.
Sucrose
The sucrose concentration of a sample can be varied to create
continuously variable particle sizes. For a given conductivity and
flow rate, the diameter of the primary droplets produced by the
Electrospray will remain the same. Once the liquid evaporates from
the primary droplet, the sucrose contained within the volume of the
primary droplet will determine the resulting particle diameter.
The resulting particle diameter D
p
may be calculated using the
formula D
p
= 150 (
ϕ
)
1/3
, where 150 being the primary droplet size
1
in
nm and
ϕ
being the sucrose volume fraction per unit volume buffer.
For example, at
ϕ
= 0.1 (10% volume sucrose per unit volume
buffer), the resulting particle diameter will be 69 nm. At
ϕ
= 0.001,
the particle diameter will be 15 nm. The maximum particle
diameter that may be created is 78 nm at
ϕ
= 0.143 reflecting
smaller droplet sizes at higher concentrations.
1
The viscosity of sucrose solutions may vary by concentration, influencing the flow rate and, thereby, the primary
droplet size. Refer to Morison (2002) for more information.