10 Replies Latest reply on Jun 18, 2018 2:00 PM by mmcmenamin

    CDS2 sample prep issues

    mmcmenamin

      My lab recently switched from CDS1 to CDS2 and one of our LC methods is now not working consistently/correctly.  We need a sample prep in which 10ul from one vial is injected to the sample vial, followed by 55ul from another vial followed by mixing and a wait period before injecting. We have tried multiple things including mixing in the seat vs, the sample, vs the air as well as drawing the liquid before mixing and not drawing before mixing and we cannot seem to get consistent results through any of this trouble shooting.  Could anyone give an example of a basic mixing method that has worked in case we are missing some obvious step that is causing inconsistent results.  Below is the example of our sample prep method on an Agilent 1260 with CDS2 software.  Thank you!

       

      sample prep.png

        • Re: CDS2 sample prep issues
          ryoboyle

          Hello,

           

          I added tags to this post to increase visibility.

          • Re: CDS2 sample prep issues
            ryoboyle

            What revision of OpenLAB CDS 2.x are you running and what revisions firmware do your 1260 modules have loaded?

              • Re: CDS2 sample prep issues
                mmcmenamin

                CDS version 2.1

                 

                controller: B.02.21[0003]

                Pump: A.07.01[001]

                MLS: D.07.20[0008]

                TCC: A.07.02[0001]

                MWD: B.07.20[0007]

                FD: A.07.02[001]

                  • Re: CDS2 sample prep issues
                    ryoboyle

                    Thank you!

                     

                    Can you also tell me what revision of LC driver you are running in your OpenLAB CDS 2.1 installation? This can be found by going to File>About in your acquisition window:

                     

                     

                    And by CDS1, what software do you mean? OpenLAB ChemStation? Do you know what revision of ChemStation and LC driver you were using?

                        • Re: CDS2 sample prep issues
                          ryoboyle

                          That is a pretty big jump from OpenLAB ICM 3.3.2 to OpenLAB CDS 2.1. If this mixing method worked on this instrument previously and no other changes were made to the instrument (i.e. firmware) then it is possible this could be caused by the LC instrument driver.

                           

                          Before diving into that, I think it would be good to have someone with LC expertise look at mixing method and determine if there is anything that might be improved. I am going to move this post to the LC section of the community to improve its visibility to such users.

                           

                          Also, would you mind elaborating on what you mean by "cannot seem to get consistent results". Are you having issue with your peak area reproducibility or peak shapes?

                  • Re: CDS2 sample prep issues
                    wydnaa

                    Hello!

                     

                    In the past, to get efficient mixing of samples like this in low volume vials or vials with inserts, repeated (3x I think) drawing maximum volume (or the total sample volume) from low in the vial (below the default position), and ejecting from high in the vial (above the default position) seemed to work well for me.  I'm pretty sure we did these at pretty high draw and eject speeds too!

                     

                    Hope that helps.

                    /Andy

                      • Re: CDS2 sample prep issues
                        mmcmenamin

                        Thank you Andy ! we will have to try this! Although it seems to be a software issue. I think there is a bug because we will have a sequence work, that we changed nothing from the original in which it did not work.  But as soon as lines are added, removed or some other non-method altering change is made, the peak areas change, sometimes causing no peak to elude at all. We've had 2 sequences made, both by the same user, that work. Then a different user will use that exact sequence, with expected results. But once another user changes the sequence, as stated before, the method no longer produces the expected results.

                      • Re: CDS2 sample prep issues
                        dannymobbs

                        Hello,

                         

                        Which Multisampler do you have A or B, and what is the exact configuration? I need to know which metering device volume and which loop volume is installed.

                         

                        Your injector program (line 5) has you drawing 100ul and then trying to mix. If you have a 100ul metering device the syringe has nowhere to move to and the subsequent mixing will not be good.

                         

                        Thanks in advance,

                        Danny

                          • Re: CDS2 sample prep issues
                            mmcmenamin

                            Hello Danny,

                             

                            According to our manual it seems we have a 100uL metering device/ sampling loop. So this may be part of our problem, however I am not sure if this solves our software issue. Thank you for the input, we will have to try a different volume before mixing!

                             

                            Thanks!

                             

                            Mychaela