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signal-to-noise ratio over the wavelength range of your analysis (see the next
section, “Optimizing the signal-to-noise ratio”).
Optimizing the signal-to-noise ratio
To optimize signal-to-noise ratios, choose an acquisition wavelength range
that includes only the wavelengths of interest. It is also important that the
range be one in which the mobile phase absorbs only minimally. You can also
improve the signal-to-noise ratio by increasing the spectral resolution value.
For example, you can choose to operate at 3.6 nm instead of at 1.2 nm
resolution. The signlal-to-noise ratio is also impacted by the filter-time
constant and the sampling rate.
Filtering data
On the General tab of the PDA Instrument Method Editor you can apply an
optional noise filter (via the Digital Filtering parameter) to the data acquired.
See also:
The Empower or MassLynx online Help.
The detector uses a Hamming filter to minimize noise. The filter is a digital
finite-impulse-response filter that creates peak-height degradation and
enhances the filtering of high frequency noise.
The behavior of the filter depends on the filter-time constant you select.
Increasing the filter-time constant reduces baseline noise, improving
signal-to-noise. However, increasing the filter-time constant too much will
artificially broaden the peak and reduce chromatographic resolution.
You can choose among these options when programming a filtering time: Fast,
Slow, Normal, or Other. If you select a fast, slow, or normal filtering time, you
need not specify a value, because the he filtering constant is determined by
the data rate. If you select the Other option, you can specify a value.
Nevertheless, the value you enter is rounded up or down to a value based on
the data rate. Selecting Other and entering a value of 0.0 disables all filtering.
The following table lists the digital filter settings for the allowable data rates.
Digital filter settings for data rates:
Data
Rate
Slow Normal Fast
1 4.000 2.000 1.000
2 2.000 1.000 0.500