Comparison of the reliability of the identification with diode array detector and mass spectrometry

The reliability of compound identification by low resolution mass spectrometry (MS) was quantitatively compared with that for diode array detection (DAD). The quantity of the information obtained with one parent ion and two characteristic daughter ions at low resolution MS–MS was compared with that obtained by UV–vis spectra with large wavelength range from DAD. It was shown that if the UV–vis spectra are reproducible, i.e. with low RSD values for selected wavelengths and relative absorption, the reliability of the identification with DAD is comparable with the one for low resolution MS–MS. Because the sensitivity of the DAD is one or two orders of magnitude lower than that of mass spectrometry, on-column focusing was applied and reliable identification was achieved at 1 ppb concentration. The surprisingly high reliability of identification obtained with contemporary DADs should increase the analysts’ confidence in this method of detection/confirmation.