LC-PDA and LC-ESI-MS separation and determination of process-related substances arising from stilbene-type fluorescent whitening agents. Application to monitoring of their photodegradation products in industrial effluents and aqueous environmental systems



A simple and rapid gradient elution high-performance liquid chromatographic method using photodiode array and electrospray ionization mass spectrometric detectors was developed for separation and determination of the process-related substances and photodegradation products of stilbenesulfonic acids, viz. 4,4´-dinitrostilbene-2,2´-disulfonic acid (DNSDA), 4-amino-4´-nitrostilbene-2,2´-disulfonic acid (ANSDA), and 4,4´-diaminostilbene-2,2´-disulfonic acid (DASDA) in industrial waste waters. Gradient elution was carried out using ammonium acetate and acetonitrile as mobile phase and an Inertsil-ODS 3V column for separation. The negative-ion electrospray ionization mass spectra containing [M–H] ions of sulfonic acids allowed molecular mass determination of unknowns and the structures were proposed on the basis of the fragment ions in the MS/MS spectra.