36
Calibration
4000 MiD® Instructions, V6695
5.
Start a timer when the liquid meniscus reaches the first visible gra-
duation on the flow meter tube.
6.
Measure the time taken for the liquid meniscus to travel over a num-
ber of graduations.
7.
Stop the timer when the mobile phase reaches the desired gradua-
tion on the flow meter tube.
8.
The output flow rate can now be calculated using the following equa-
tion:
Flow rate (µL/min) =
Note:
The measured flow rate should be slightly higher (~20%) than the
desired flow rate defined from the spit ratio
9.
If the flow rate is not as expected, repeat the measurement using
steps 3-8.
10.
If the measured flow rate is still incorrect, the next step is to clean the
DFI/SFI see section 8.5 below.
The same procedure can be used to measure the output flow when a
custom split ratio is created for an SFI (see„5.8.1 The Split Flow Interface
(SFI)“ on page 23). If the measured flow is incorrect the user can simply
change the length or diameter of the waste line and re-measure the flow
rate.
9.5 Spraychip assembly cleaning
The DFI and SFI can both be flushed and cleaned. The flow meter assem-
bly will be required to follow the procedures in this section.
9.5.1 Cleaning the Direct Flow Interface
The following procedure should be used to clean the DFI.
1.
Fill a syringe with a 50:50 (v/v) mixture of HPLC grade methanol and
water with no additives and mount in a syringe pump.
2.
If fitted remove the spraychip from the DFI (see „8.2 Removing and
replacing the spraychip“ on page 33).
3.
Screw the flow meter adaptor into the DFI (Fig. 35) using the same
procedure as when fitting a spraychip (see
).
Fig. 21
DFI with flow meter adapter
Number of divisions
Time/min
Procedure
flow meter
adapter
DFI