46 Agilent Cary 8454 UV-Visible Spectroscopy System Installation Guide
3 Good Measurement Practices
General Considerations
When using volatile solvents such as acetone or methylene chloride, make
sure that the sample cell is stoppered. Evaporation of a solvent can
change the solute concentration or cause solution noise due to solute
convection currents. Both of these will affect the accuracy of your
measurements. We also recommend stirring and temperature control when
you use volatile solvents.
When using water as solvent we recommend using UV grade or HPLC
grade water to reduce unwanted absorbance from the water. If you are
using the sipper/sampler system the water should be degassed to avoid
bubble formation in the flow cell, especially if the water comes from a
pressurized water supply.
Sample Preparation
The sample cell should be rinsed three to five times with your intended
solvent before you fill it with the pure solvent that will be used in the
measurement. Turning the cell upside down on a small stack of absorbent
tissues will help remove any residual solvent. This treatment will minimize
contamination from previous experiments.
Samples which contain colloidal dispersions, dust or other particulate
matter should be filtered, centrifuged or allowed to settle. If not, the
overall attenuation- of- transmittance spectrum due to light scattering
and/or reflection will hide the spectral information from the analyte.
Many of the solvents in Tab le 1 are hazardous. Be sure you fully understand their
properties before using them.
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