Ocean Optics DTS - Manual (Page 48)

Chapter 6
6-2 Polychromix DTS TM Near-Infrared Spectrometer
Operator’s Manual
Document Number 04-91-0201-00 Rev A
6.2 Using a Cuvette and Sample Holder
6.2.1 The Cuvette
A cuvette and a sample holder are used when the spectrum of a liquid is to
be obtained. The standard cuvette has a 1 cm path length (although other
lengths may be used)
and requires approximately 2 mL of sample. If the
available sample is less than 2 mL, a number of smaller cuvettes are
available and an adapter can be used to reproducibly position the cuvette.
NOTE: It should be noted that the absorbance of a sample is
proportional to path length, and using a smaller cuvette will be
beneficial for samples with large absorbance values.
The cuvette is an integral part of the optical system, and should be handled
with care. The following points should be noted to ensure the fidelity of
collected spectra:
•
Always place the cuvette in the light path so that the same wall plane
faces the incoming light to ensure a constant path length.
•
Do not get fingerprints on the optical faces of the cuvette. If you
accidentally touch an optical surface, wipe it off with a lint free tissue
saturated with methanol and allow the methanol to evaporate.
•
If an optical surface of the cuvette is scratched, chipped or becomes
cloudy, position the cuvette in the sample holder so that the light does not
go through that surface.
6.2.2 The Sample
The sample should be dissolved in a suitable solvent and should be
homogeneous. Spectroscopic grade or other highly purified solvents should
be used whenever possible. If the source of the solvent is changed, verify
that the new solvent and the old solvent are equivalent and collect a new
background spectrum.
If the sample contains particulate matter, make sure that it is filtered to
remove the solid material.
If there are air bubbles in the sample, remove them before taking a
measurement. Air bubbles are occasionally observed in aqueous samples
that have been allowed to sit undisturbed for a period of time.