There are three signs that a Polyarc may be due for replacement. The indicators all have different potential causes. Sometimes they share commonalities with other GC issues. Regardless, it is beneficial to have a baseline chromatogram to compare new tests with. You can use the Polyarc Test Mix or another applicable known mixture for your baseline tests. We can use this comparison to determine changing trends and identify an issue before it wastes valuable laboratory time. The three signs for a replacement are tailing peaks, loss in response, and inaccurate quantification. 

As explained in the previous replacement blog, tailing peaks can be caused by active sites in the Polyarc. This may be from silicon deposits or exposure to atmospheric conditions when hot. Unfortunately, there is no guaranteed way to fix this issue. Some success has been seen by trimming off a portion of the Polyarc inlet transfer line. Tailing peaks will commonly occur for active compounds. You can identify active compounds by their polarity. In the ARC Test Mix aniline and chlorophenol will first show signs of tailing over a straight chain alkane. Other compounds containing highly electronegative compounds have greater interactions with material in the flow path. Silanol species contain an O-H group that will cause the analytes to drag through the GC and result in poor peak shape. All new Polyarcs have an inert flow path and are QC tested for accurate quantification and correct peak shape. Exposing the Polyarc to ambient atmosphere while still hot can create active sites leading to tailing. Tailing is a sign of an active flow path. If possible, the fastest way to determine whether the Polyarc is due for a replacement is to complete a run with and without the Polyarc. Isolating the GC system can highlight when contamination in the inlet or column are causing tailing. 

April 22, 2022