What are the major components of an analytical sample cell?
A typical cell has three components: a window assembly, centerpiece and housing.
- AUC cells require two window assemblies (top and bottom)
- Windows can be quartz or sapphire
- Quartz works well for absorbance measurements and sapphire works better for interference
- Epon (epoxy) centerpieces are most common and can be spun ≤ 42,000 RPM
- Solid aluminum centerpieces can be spun ≤ 60,000 RPM and require an extra gasket on both sides
- Higher-concentration samples require a smaller, 3mm centerpiece to allow more light to pass through
- Two-cell centerpieces can be used for SV and SE measurements
- Six and eight sector centerpieces are used primarily for sedimentation equilibrium (SE) measurements
- This has the same number of fill holes as the centerpiece used, with a key to help line up all parts correctly
- A typical two-hole assembly might look like this: