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C190-E167










                                         New Data Processing Method for
            Technical
            Report                       Photodiode Array Detector
                                         Principle and Summary of i-DReC (Intelligent Dynamic
                                         Range Extension Calculator)

                                         Toshinobu Yanagisawa 1


            Abstract:

            A new data processing method for a photo diode array (PDA) detector, Intelligent Dynamic Range Extension Calculator (i-DReC) enables the
            automatic calculation of peak area and height, utilizing spectrum similarity in the high concentration range where UV signal is saturated. When
            the integrated chromatographic peak area exceeds a user-defined threshold value, i-DReC automatically shifts the chromatographic profile to a
            wavelength with less UV absorption to prevent signal saturation. The absorption ratio between the original target wavelength and the
            wavelength used by the i-DReC function is applied as a correction factor to the peak area of the acquired chromatogram, thereby calculating the
            peak area and height at the original target wavelength. The i-DReC dramatically extends the linear dynamic range of calibration curves, enabling
            reliable quantitation of high concentration samples without need for sample dilution and reinjection, which would otherwise be required.

            Keywords: PDA data processing, dynamic range extension, Nexera X2, UHPLC




            1. Basic Principle of i-DReC                         5. An absorption ratio (k) is calculated from the spectrum in (4).
                                                                  The intensity (Ia) of the spectrum at λa is divided by the intensity
            High concentration samples can produce saturated UV spectral ab-  (Ib) of the spectrum at λb, as follows:
            sorbance, which significantly affects peak area calculation and
                                                                  k=Ia/Ib
            causes a loss of linearity in the relationship of peak area to concen-
            tration. The i-DRec calculates an absorbance ratio between the   6. Peak area and height of the measured peak in the chromato-
            original target wavelength and another wavelength that provides   gram at λb are corrected by the absorption ratio to determine
            less absorbance in a spectrum on the down-slope of the chromato-  the effective area and height at λa, as follows:
            graphic peak where neither wavelength's absorbance is saturated.   Peak area at λa = (peak area at λb) × k
            The corrected peak area and height are then calculated by multiply-  Peak height at λa = (peak height at λb) × k
            ing the measured peak area and height by the absorbance ratio.               Extraction of chromatogram at λb
                                                                      mAU
                                                                     4000 λa nm
              Calculation Algorithm
            1. i-DRec is automatically applied when the intensity of a target
                                                                          Threshold
              peak exceeds the user-defined threshold value. If the threshold  level
                                                                                                      λb nm
              value is not exceeded, i-DReC is not applied.
            2. The wavelength used for correction by i-DReC (λb) can be set   0
              either manually or automatically. When set manually, λb is a us-
                                                                                    Extraction of
              er-defined parameter. When set automatically, λb is determined        spectrum for
                                                                                    sensitivity correction
              as follows:                                             mAU
                                                                          Signal intensity for
                                                                          extraction of sensitiity   Absorption ratio
               A UV spectrum is acquired at the retention time of the target peak.  correction spectrum  is calculated by Ia
                                                                                              and Ib
                The spectrum is analyzed to determine an appropriate wavelength
               for which the absorbance is not saturated, which is then set as λb.   Sensitivity   k =  Ia
                                                                              Ia   correction        Ib
            3. The chromatogram at λb is extracted from the 3D data and inte-     spectrum
              grated to determine peak area and height.
            4. A UV spectrum is extracted from the chromatogram (at the orig-            λa
              inal target wavelength (λa)) at a point on the down-slope of the
                                                                              Ib     λb
              peak (between the peak apex and peak end) where the absor-
                                                                                λ
              bance of neither λa nor λb are saturated.
                                                                             Fig. 1  Basic principle of i-DReC
            1. Analytical & Measuring Instruments Division
                                                                                                                      1
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