52 Agilent Cary 8454 UV-Visible Spectroscopy System Operator’s Manual
4 Good Measurement Practices
General Considerations
General Considerations
There are many factors that can affect the results of your measurements. This
section provides brief discussions of some of the more important ones.
Spectrophotometer Design
The sample compartment of the spectrophotometer is open. Unlike
conventional instruments the UV-Visible spectrophotometer does not suffer
from ambient false light. The open sample area makes it easier to access it
generally and to connect tubing to a flow cell or thermostattable cell holder.
Making Measurements
Blank (Reference) and Sample Measurement
Your spectrophotometer is a single beam instrument so you must measure a
blank before you measure a sample. For the high accuracy measurements, the
blank and the sample measurement should closely follow each other.
In general, a blank measurement should be repeated as often as is practical.
Even in a thermally stable environment, a blank measurement should be taken
at least every half hour to ensure accurate results.
Chemically, the only difference between the blank and the sample should be
the presence of the analyte(s). For measurements with liquid samples, the
blank should be a sample cell filled with the solvent you plan to use.
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