Waters 2489, Руководство оператора

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1-14 Theory and Principles of Operation
The major difference between the detector and a double-beam
spectrophotometer is that the detector employs only one flow cell or cuvette,
rather than a simultaneous sample and a reference pair.
Recommendation:
Use a matched pair of cuvettes for the zero and sample
scans.
The detector obtains an absorbance spectrum by performing two types of scan
on the flow cell or using the cuvette:
• Zero scan – Characterizes the baseline absorbance spectrum of a solvent.
• Sample scan – Subtracts the zero scan, so the results displayed or
charted are of the sample only.
To obtain a spectrum of a sample with the detector, you need to run a zero
scan first, followed by a sample scan. Typically, the zero scan is run with pure
solvent and the sample scan is of the analyte dissolved in that solvent.
Spectra can be simultaneously charted on the channel A output, or acquired
and stored in memory for later playback.
See also: “Scanning using the cuvette” on page 3-59 and “Scanning using a
flow cell and a syringe” on page 3-62 .
Cuvette operations
The detector cuvette option is used to measure the absorbance spectrum of a
sample in a cuvette.
To generate and store a spectrum:
1. Acquire a zero scan, which measures the absorbance of the contents of
the cuvette and flow cell over the desired wavelength range.
2. Acquire a sample (absorbance) scan, which measures the absorbance of
the analyte dissolved in mobile phase.
The detector subtracts the zero scan from the sample scan to create a sample
spectrum.
Since the cuvette scan is acquired by measuring the absorbance from a light
path that includes both the flow cell and the cuvette, the solvent conditions in
the flow cell should be identical for both scans. For a detailed explanation of
cuvette scanning, see
“Scanning using the cuvette” on page 3-59 .