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Product information
4000 MiD® Instructions, V6695
significantly reduces the equipment noise, footprint, and size. This also
eliminates complications associated with rotary pumps, such as back-
stream of pump oil and the added expense of purchasing an oil trap.
The vacuum system comprises three sections:
The vac-chip interface
The ion guide chamber
The analytical chamber
The pressures in the chambers are monitored using Pirani gauges which
also act as high-voltage interlocks. These gauges turn off any high volta-
ges if the pressure readings in the chambers are above a set safety value.
3.1 Theory of microspray
Microspray is a soft ionisation technique. A voltage, generally between
0.7 and 1.5 kV, is applied to an analyte dissolved in a suitable solvent;
generally a mixture of water and an organic solvent. The solvent passes
through an emitter or capillary tip at a flow rate of 300-1000 nL/min. The
voltages and flow rates used in microspray are lower than for convention-
al electrospray ionisation. This means that lower volumes of sample and
solvent are consumed by the MiD. When coupled with a nano-flow LC,
solvent consumption is reduced by several orders of magnitude when
compared to traditional HPLC systems.
Under the correct conditions, a plume of charged aerosol droplets forms
from a Taylor cone. Gas-phase analyte ions are subsequently formed from
these aerosol droplets. Ions produced by this method can have single
or multiple charges. Generally, high molecular weight compounds, for
example, proteins, produce a series of multiply-charged ions.
3.2 Views
3.2.1 The front panel
Fig. 1 shows the connections and ports on the front panel of the MiD.
Refer to the labels listed in the table below during operation.
Connection
Description
K
USB Port
L
On/Off Power switch
M
LED Status Indicators
N
Spraychip assembly high voltage connection
