PerkinElmer Lambda 25, Руководство пользователя

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Lambda 25, 35, 45 User’s Guide
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The absorption characteristics of a sample can be changed during sample
preparation, depending on the amount of reagent added for color development and
so on. For details, refer to reference books covering these subjects.
Temperature has an influence to a greater or lesser degree on the absorption
characteristics of a sample. You should check this effect if non-repeatable results are
obtained.
If you are measuring temperature-dependent samples, either wait until temperature
equilibrium has been attained or use a thermostatted cell or cell holder.
Chemically Reactive Samples
If a reaction takes place in the cell between the sample material and the solvent,
spectral data based on that sample cannot always be expected to have sufficient
reliability or repeatability.
For samples of this type, use a quantitative method that takes advantage of the
change in transmittance with time at a fixed wavelength. For details, refer to
reference books covering this specific subject.
Photoactive Samples
Some samples are known to be photoactive in that they fluoresce upon absorbing
radiation. Since a small portion of the fluorescent radiation will be measured by the
detector, a higher apparent transmittance will often result.
Samples are also known that undergo photochemical reactions as they absorb
radiation. With such samples, which are mostly biochemical, lack of reproducibility
will characterize the resultant data.
Other Sample Properties
Samples that are polarizing in nature, or have a double index of refraction, are often
difficult to measure accurately. The emerging monochromatic radiation is slightly
polarized due to having been refracted.
Thin-film samples also pose a problem since optical interferences may develop,
causing a regular interference pattern to be superimposed on the spectral curve.
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