INFICON PLO-10i Phase Lock Oscillator - Manual (Page 42)

PLO-10 PHASE LOCK OSCILLATOR
CRYSTALS, HOLDERS AND FLOW CELL 7-8
dry the crystal. It is better to chase liquid off the crystal than to let it evaporate off the
crystal.
♦ Never wipe the crystal – even soft, lint-free cloth will scratch the crystal.
7.2.1 CRYSTAL CLEANING
The surface properties of the sensor crystal determine the interaction of sample material
with the surface. Therefore, the developments of proper procedures for cleaning are
required to obtain meaningful and reproducible measurements. This section provides the
basic information you need to develop a cleaning procedure suited to your sample/surface
preparation.
CAUTION
– When developing a cleaning procedure, always perform
a test run on a crystal before committing to a larger batch cleaning.
Follow the crystal handling guidelines throughout the cleaning process
to protect the crystal quality. Avoid using high pH cleaners since they
will etch the crystal surface.
7.2.1.1 General Cleaning
For general purpose applications such as electrochemistry and liquid or viscoelastic film
experiments, it is usually sufficient to use ultrasonic cleaning method to clean the crystals
in a solution of non-basic detergent in deionized water. Immediately rinse liberally with
deionized water and dry in a gentle flow of filtered nitrogen gas.
7.2.1.2 Organic (hydrocarbon contaminants)
UV/ozone treatment 12 is a powerful tool for removing hydrocarbon impurities which
have been adsorbed from the ambient air. This method utilizes irradiation with ultra
violet light that breaks up the organics on the surface of the sample being cleaned. A
flow of air or a weak vacuum carries off the organics. This method does not affect the
quartz surface; it is low cost and is very efficient.
Oxygen plasma cleaning is another effective method that will remove organic matters. In
this method, the plasma reaction breaks up organic matters at the surface of the sample
being cleaned into smaller molecules and a vacuum pump removes them from the surface
of the sample.
7.2.1.3 Biomaterials (lipids, proteins and similar biomolecules)
Start by treating the crystal in an UV/ozone chamber for 10 minutes, then immerse it into a
1:1:5 solution of hydrogen peroxide (30%), ammonia (25%) and deionized water heated
to a temperature of about 75°C for 5 minutes
22
. Immediately rinse liberally with
deionized water and dry in a gentle flow of nitrogen gas. Immediately before
measurement, treat the crystal with UV/ozone for 10 minutes.
7.2.1.4 Lipid vesicles on SiO
2
surfaces
Treat the crystal in an UV/ozone chamber for 10 minutes, then immerse it into water with
2% of sodium dodecyl sulfate (SDS) at room temperature for 30 minutes
23
. Rinse
generously with deionized water and blow dry with filtered nitrogen gas. Immediately before
measurement, treat the crystal with UV/ozone for 10 minutes.