51
Appendices
4000 MiD® Instructions, V6695
Appendices
Appendix A: Flow Splitting
In its simplest form, a flow splitter is composed of a union or tee with
tubing of various inner diameters attached as shown in Fig. 48.
Fig. 34
Basic flow split
The split ratio can be changed by changing both the inner diameter
and the length of the waste line (high flow tube).
The split ratio varies with the input flow rate and liquid composition
(changes during a gradient).
Flow rates can be measured using the flow meter assembly, see chap-
ter „8.4 Liquid flow rate measurement“ on page 35.
For a fixed length decreasing the diameter of the waste line increases
the spraychip flow rate.
For a fixed diameter increasing the length of the waste line increases
the spraychip flow rate.
Changing the diameter of the waste line has a greater effect on the
split ratio than changing the length.
The split ratio (R) is the ratio of the flow rates exiting the high flow tube
and the low flow tube. This is dependent on a number of factors including
the properties of the fluid, for example, viscosity. However, the following
equations can be used to calculate the split ratio for the MiD.
Equation 1
Where
DHF – Inner diameter of the high flow tube in microns
LHF – Length of the high flow tube in centimetres
DLF – Inner diameter of the low flow tube in microns
LLF – Length of the low flow tube in centimetres
Low flow tube
(spraychip 200)
High flow tube
(waste line)
Input flow
(e.g. LC)
