Page 65 - LC-SFC_Pharma_Brochure

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