Prepare your solutions carefully, Avoid using a stirrer, For operation with the fc-550 flow cell – INFICON RQCM - Quartz Crystal Microbalance Research System User Manual
Page 35: Avoid excessive differential pressure, Keep a constant line pressure, Prepare your solutions carefully -11, Avoid using a stirrer -11, For operation with the fc-550 flow cell -11, Avoid excessive differential pressure -11, Keep a constant line pressure -11
RQCM – RESEARCH QUARTZ CRYSTAL MICROBALANCE
OPERATION
3-11
3.9.4.4
Prepare Your Solutions Carefully
To avoid effects due to changes in the properties of the buffer liquid or solvent, solutions should
be prepared carefully. Whenever possible, use purified samples at high concentration and dilute
them in the appropriate buffer or solvent just before measurement. Use solvents or buffers from
the same stock during one measurement.
3.9.4.5
Avoid Using A Stirrer
If possible, avoid using a magnetic stirrer. Stirrers create turbulences. However, many solutions
often require the use of a magnetic stirrer to keep a solution well mixed. If this is the case, keep
the stirrer rotating speed constant throughout the experiment.
3.9.5
FOR OPERATION WITH THE FC-550 FLOW CELL
The FC-550 is used in place of the Crystal Retainer Ring to create a flow chamber of ~ 0.1 mL.
This setup can be used for either gas or liquid flow. In both cases, observe the following tips to
avoid unwanted effects in the measurements.
3.9.5.1
Avoid Excessive Differential Pressure
The differential pressure from the front to the back of the crystal must be minimized to avoid
frequency errors due to stress on the crystal and to avoid crystal breakage. INFICON’s 1-inch, 5
MHz, AT cut crystal will fracture at pressure differentials above 5 PSI.
3.9.5.2
Keep a Constant Line Pressure
Using a pumping system that minimizes pulsation and maintains a constant line pressure
throughout the experiment. A syringe pump is a good choice because it provides pulse-less flow.
If a peristaltic pump is used then it is better to pull the liquid through the flow cell to reduce
frequency fluctuations caused by pulsing. Gravity flow is another good method for flowing fluid
through the cell without the pulsation effects. However, the line pressure does change as the
volume of the fluid reduces in the reservoir. Care must be taken to maintain the volume in the
reservoir.
3.9.5.3
Allow Ample Time For the Crystal To Come to Equilibrium
Expose the flow cell’s chamber and the sensor crystal to the medium. Wait for it to come to
equilibrium and establish a baseline prior to making measurements.