Figure 4. Times series plots of channel b chromatographic peak areas for calibration samples injected at South Pole between 01/20/95 and 05/20/95 (i.e. days 20 - 140 of the year 1995). CFC-11 (F11 in the right-hand margin of each plot) is shown in red, CFC-113 (F113) in green, CH₃CCl₃ (MC) in blue, and CCl₄ (CT) in black. The plot of the original chromatogram analysis (top frame) shows numerous intermittent occasions when CH₃CCl₃ and CFC-113 were not picked up by the peak analysis software. This often occured throughout the areas/heights database because of an excessively-constrained analysis method. The problem was addressed by reanalyzing chromatograms (examples) utilizing a method with softened constraints (bottom frame). This illustration also shows two regions where CCl₄ was mistakenly identified at CH₃CCl₃ (top frame; see also Figure 3).