14. Disturbances
FlowStar2 LB 514
124
Luminescence caused by incomplete mixing
The mixing process in the measuring cell is not yet completed. One reason
is, for example, that the scintillator mixes only badly with the solvent. In
addition to heat, light and luminescence are also generated. Open the
measuring cell inlet, put the stainless steel capillary in a transparent glass
container and let the cocktail flow off inside the glass. An incomplete mixing
process is indicated by the fact that streaks are still noticeable.
Remedy:
In most cases the desired homogeneous mixture can be obtained with a
longer (30 - 50 cm) pinch-type capillary mixer.
Increase, in some cases “reduce”, the scintillator share in the cocktail.
Flash effect
Interference in solid cells. With some purely organic, non-conductive sol-
vents (n-Hexan, chloroform) static charge effects are noticeable at a higher
flow rate. The friction of the molecules produces a static voltage which is
not carried off due to the high resistance of the eluate. Consequently, the
voltage is discharged and high-energy flashes of light (flash effect) occur
which cause interference in both discriminator channels. The interference
still persists even when the flow rate has been stopped and decreases only
very slowly.
Remedy:
1. Interference disappears suddenly when adding a small amount (1-3%)
of conductive solvent (e.g. Methanol).
2.
Use “D”-cells which include a “conductor” on the inside, e.g. the cells
YG-150 D, YG-150 U5 D.
