Sample Cell / Mobile Fill Station FAQ

Q: The literature says to clean and dry before filling with sample. Is this required between each sample measurement or just at the start of the testing?

• Yes, you should clean and dry the sample cell between each sample measurement, not just at the start of testing.

Q: Should we be running a blank in between each sample if all samples utilize the same solvent?  

• No — if all samples use the same solvent, you do not need to run a blank between each sample, provided your polarimeter and conditions remain stable

• The blank sets the baseline once.
  Running a solvent blank (pure solvent) establishes the zero point that corrects for any optical rotation from the solvent, sample cell, and optics. Once that’s done, the instrument applies that same correction to all subsequent samples.

• The solvent’s effect doesn’t change.
  As long as every sample uses the same solvent under the same temperature and wavelength, its optical contribution remains constant — so a single blank remains valid.

• Unnecessary blanking adds variability.
  Each time you re-zero or re-blank, small differences in temperature, solvent purity, or alignment can introduce slight shifts, which can actually reduce consistency across measurements.

Q: For the Zero Normal 0.000 button, it seems that this button is pressed when blanking the instrument with the solvent, but what exactly does it do?

• When you press Zero, the polarimeter measures the current optical rotation reading — usually with the cell filled with pure solvent (the blank) — and then sets that reading as the reference point of 0.00°.

Q: Is there any harm in pressing this button in between sample measurements?

• There’s no physical harm in pressing the Zero button between samples,
  but it’s not recommended unless you have a specific reason to do so.

• When you press the Zero button, the polarimeter takes whatever optical rotation it’s currently seeing (even a tiny residual rotation, alignment shift, or temperature drift) and sets it as the new baseline.

  That means all subsequent readings will be measured relative to that new zero — not the original one.

• You may introduce baseline drift or inconsistency.
  Each new “zero” can be slightly different due to tiny changes in solvent, temperature, or optical alignment — even if everything seems stable. Over time, that can make your results less comparable from sample to sample.

• You could accidentally zero over contamination.
  If a trace of the previous sample, residue, or bubble remains in the cell, pressing Zero will “normalize” that error — and all your next readings will be off.

• You lose your verified blank reference.
  The solvent blank you ran at the start establishes a trusted baseline. Re-zeroing replaces that with a new, unverified reference.