INFICON Explorer Portable Gas Chromatograph - Manual (Page 181)

Explorer Operator Manual
179
Filter
Since baseline noise is constant throughout the chromatogram, the reduced slope
sensitivities may allow false noise peaks to be detected. To reduce these effects, the
integrator filters the signal by averaging the signal over larger periods while
reducing the slope sensitivities. This allows the signal to noise ratio to remain
constant throughout an analysis giving good integration on both early and late peaks.
It is not possible to select a single filter that will work ideally under all conditions,
because of variations in carrier flow and column temperature in a GC. If data are too
heavily filtered, adjacent peaks will not be resolved, while if too lightly filtered,
noise creates unwanted peaks. In either case the quality of the integration will suffer.
Filter 1 provides the most filtering with the signal being averaged over the longest
period before the slope is calculated. Filter 4 provides the most versatility; the signal
is analyzed simultaneously by four different filters.
The highest filter level is used to detect the start of each peak. Once a peak is
detected 1, 2, 3 or 4 of the other filters (depending on the Filter selected) will
operate on the same data until they detect integration stop points.
The end result is detection of large peaks since all data are heavily filtered as well as
good resolution of small peaks since all data are also analyzed with relatively little
filtering. When the signal noise is low, select Filter 4. For noisier signals, select
lower Filter numbers. Filter 4 also provides better resolution for co-eluting peaks.
Merged Peaks
Merged peaks are separated in one of two ways. Explorer will draw either a
diagonal or vertical line depending on where the peaks overlap.
Again, as with normal peaks, when the integration stops, the area below the baseline
is subtracted and the resulting peak areas are stored for calculation.