Figure 5. Time series plots of chromatographic CFC-12 peak areas from air and calibration samples injected at the South Pole between 05/10/94 and 08/03/94 (i.e. days 130 - 215 of the year 1994). Air samples were injected from two seperate sample streams shown here in green (AIR1 in the right-hand margin of the plots) and black (AIR2). Calibration samples were injected from two seperate working standards tanks shown here in red (CAL1) and blue (CAL2). The plot of the original peak analysis (top frame) shows a considerable degree of instability resulting from an insufficiently-constrained analysis method. This allowed a chromatographic feature just ahead of the CFC-12 peak to intermittently interfere with the software's determination of the starting point for the peak. This type of situation occurred in several places throughout the areas/heights database and was addressed by reanalyzing chromatograms under tightened constraints (bottom frame).