14 Replies Latest reply on May 14, 2018 8:07 AM by ryoboyle

    OpenLAB CDS Peak area problem

    kingsley

      Hi Everyone,

       

      I am using Agilent 1200 with openLAB CDS for the analysis that I am doing. I am plotting a standard calibration curve but I observed that the peak area does not increase as the concentration increases. The peak area provided by the integration output does not follow a defined order. Does anyone know how to solve this problem? I hope to hear from someone soon.

        • Re: OpenLAB CDS Peak area problem
          valentinrusu

          Hello kingsley, welcome! Which OpenLAB are you using (choices are ChemStation Edition, EZChrom Edition, or simply CDS 2.0, 2.1, or 2.2) and what revision? You can find out both of these pieces of information if you click Help > About; both the type of software and Revision should be right in that window. 

            • Re: OpenLAB CDS Peak area problem
              kingsley

              Hi Valentin, Thank you for the response.

               

              I am using chemstation revision A.02.01

                • Re: OpenLAB CDS Peak area problem
                  valentinrusu

                  I am assuming you’re using ChemStation Revision C.01.06 in that case. Can you confirm that’s true? I should clarify that Help > About in the actual analytical software should reveal the correct information we’re looking for. In other words, don’t look for the Revision in the OpenLAB Control Panel. 


                  Sorry to harp on this, but the advice you get will vary significantly based on the software type and Revision. 

                    • Re: OpenLAB CDS Peak area problem
                      kingsley

                      Yes your right. I am using  Rev.C.01.06[61]

                        • Re: OpenLAB CDS Peak area problem
                          valentinrusu

                          Ok, thanks for confirming! So, let’s tease out what you’re trying to accomplish. When you say that the areas are not increasing with increasing concentration, which part of the software are you referring to? If you’re looking at the calibration table, it sounds to me like perhaps you haven’t loaded more than one data file when building your concentration levels. Since by your question you’re implying that you are trying to build a multi-level calibration curve, you should have a separate corresponding data file for each concentration level. When building the curve, load the data file corresponding to the first concentration, create the first level, then move to the next file and so on. 

                            • Re: OpenLAB CDS Peak area problem
                              kingsley

                              I am not building a multilevel calibration table. I just run the standards and copy out the peak area in the data analysis section. I plot the calibration curve in excel.

                                • Re: OpenLAB CDS Peak area problem
                                  valentinrusu

                                  So you’re saying that when you inject increasingly higher concentrations for example, the data files you obtain in ChemStation don’t show higher peak areas? In that case, I would guess that either the sample preparation is problematic or the concentrations you’re injecting are outside the linear dynamic range of the detector. It might help to post your method parameters and the chromatograms that show the discrepancy to which you’re referring. 

                                    • Re: OpenLAB CDS Peak area problem
                                      kingsley

                                      Yes that is the problem. I am using porosell 120 C18 column with internal diameter of 4.6 and length of 50mm. The mobile phase is 0.1% Formic acid + water (A) and 0.1% Formic acid + Acetonitrle (B). the gradient elution time table is stated is as follows: 90% A and changing to 90% B at 6mins and finally returing to the initial conditions at 12mins.

                                      The calibration standards are prepared from 196 ul of potassium phosphate buffer at pH 7.4 and 5uL of microsomal protein followed by the addition of 1uL of standard working solutions(2ug/ml,3ug/ml,24ug/ml,48ug/ml,180ug/ml and 420ug/ml) and 10ul of acetonitrile containing internal standard was added to reach the final concentration. The solution was centrifuged and filtered using a centrifugal filter device and 10uL of the filtrate was injected onto the LC.

                                      This method is been validated for the drug metabolism studies that am doing.

                                       

                                      I hope to hear from you soon.

                        • Re: OpenLAB CDS Peak area problem
                          ryoboyle

                          Hello kingsley,

                           

                          Do you still need any help with this issue or have you found a working solution? Please let us know if you need any further assistance and we can pick it up from there. If you have resolved the problem, it would be appreciated if you could reply to this post with the solution and mark it as the "Correct Answer".

                          • Re: OpenLAB CDS Peak area problem
                            kingsley

                            HellI there,

                            Thank you for reaching out. Unfortunately, I have not been around to reply to this post. The problem has not solved.