Photodiode-Array (PDA) Detector
Definition
An HPLC detector that records a full UV-Vis absorption spectrum at every elution time point, producing a 3D data matrix (time, wavelength, absorbance) that allows both retention-time and spectral matching for each separated component.
- Instrument type
- HPLC detector
- Output
- Full UV-Vis absorption spectrum at each time point
- Data form
- 3D matrix: time, wavelength, absorbance
- Forensic use
- Retention-time and spectral matching in ink analysis
Common questions
Why is a PDA detector more useful than a single-wavelength UV detector for ink work?+
A PDA captures the entire absorption spectrum for every eluting component, letting an examiner compare both when a compound eluted and what its full spectral fingerprint looks like, rather than relying on a single fixed wavelength that could mask differences.
Can two different dyes coelute and still be distinguished with a PDA detector?+
Sometimes; if their spectra differ enough, spectral deconvolution across the peak can separate their contributions, though closely eluting compounds with very similar spectra remain a genuine limitation of the technique.
How does PDA data support a match conclusion between two ink samples?+
An examiner overlays the retention times and full spectra of separated components from the questioned and known inks; consistent retention times paired with matching spectral shapes across multiple components strengthens the association.
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