8 Replies Latest reply on Apr 12, 2019 4:06 AM by noreuter

    Can PLOT columns, specificaly those with the particle traps, be trimmed?

    jason.minter

      I am seeing a drop in Area Counts across Standards, even with fresh, new stock. I am trying to identify any other possibility besides having contaminated the column as it was just installed 4-5 months ago, but haven't had much luck. In my other lab, we had different columns and trimming was a way of life there. However, I remember reading somewhere that it was not advisable to trim these types of columns. Is this correct? I haven't trimmed this particular column yet but was beginning to think about it, and thought I should "ask the experts."

        • Re: Can PLOT columns, specificaly those with the particle traps, be trimmed?
          james_jenkins

          Hi Jason,

          I moved your post for better visibility.

          Regards

          James

          • Re: Can PLOT columns, specificaly those with the particle traps, be trimmed?
            noreuter

            Hi James,

             

            you can trim PLOT columns like WCOT columns, maybe just a little more careful when you snip the cut part away if there is no particle trap.

            If the PLOT column has a coupled particle trap you can even replace it with a new one.

            If you find a lower area count then also think of checking/removing the front ferrules, the inlet, the inlet septum or even the gold seal. It normally means you loose analyte in the injector region, can be by a leak, by absorption in the liner, a column too high mounted in the inlet, through the septum purge.

             

            Best regards,

             

            Norbert

            • Re: Can PLOT columns, specificaly those with the particle traps, be trimmed?
              jason.minter

              I should clarify that this is attached to an auto-sampling headspace analyzer. Removal of septa, liner (and thereby gold seal) is usually only done during the yearly PM in order to minimize variations. Also, the column had not been removed or re-inserted when the loss occurred, so I don't see the inlet depth being the issue. Since the samples presented are almost entirely gaseous (headspace) I am not too sure even how necessary a trim would be. I am just trying to eliminate any other possibilities other than column degradation. This column is only a few months old at the onset of area loss, and I don't want to have to replace the column that often.

                • Re: Can PLOT columns, specificaly those with the particle traps, be trimmed?
                  noreuter

                  Hi Jason,

                   

                  then your inlet should be ok. Let's talk column and components then:

                  • What column do you use?
                  • What components are analyzed?
                  • Are all components effected by the area loss?
                  • What is your detector?
                  • Where there changes in the matrix, incubation time or temperature?
                    • Re: Can PLOT columns, specificaly those with the particle traps, be trimmed?
                      jason.minter

                      Column: HP-PLOT/Q+PT 30M +5M Duraguard (2.5M on either end) 0.530 mm megabore, 40Micro film

                      Primary components residual EO and PO in various acceptor chemistries. Separate STDs for each, both are showing area decline, on FID, recently switched out flame tip due to blockage/non-ignition. Area counts were already down before blockage of flame tip, and did not return after replacement.

                      No changes to matrix or method/procedure. I had seen this issue before and finally determined that it was due to column contamination. Replaced the column in November of last year and area counts were good for 2.5-3 months. Initially thought the recent loss was due to STD age, and replaced both STD cyliders. Area counts remained low.

                      I have put a filter on our Hydrogen, carrier line, from our benchtop hydrogen generator but that may have been closing the barn door after the horses have escaped. Otherwise, I'm not sure what could be getting into the column at this point.

                        • Re: Can PLOT columns, specificaly those with the particle traps, be trimmed?
                          noreuter

                          All Q-polymers are made by radical polymerization and the process leaves free electrons (radicals) in the polymer. EO and PO are prone to radical polymerization and can react with the polymer's surface very slowly. This reaction changes the column's selectivity irreversibly. The longer a Q-column stays at high temperatures, the more migration of the free electrons take place and therefore reaction with reactive monomers like EO and PO increase.

                           

                          You could use an apolar liquid phase (100% dimethylpolysiloxane) with a very thick film (5 or 8 µm) for the separation. EO has a retention index of ca. 420 and PO of ca. 450, so they can easily be separated without any polymerization reactions.