[The separation of overlapping peaks of lanthanide complex by photoacoustic phase-resolved method]

Photoacoustic(PA) phase-resolved method is used to separate the overlapping peaks of lanthanide complex for the first time. PA peaks of Nd3+ are covered completely by the PA absorption of tryptophan(Trp) for Nd(Trp)3Cl3.H2O within 300-400 nm. The patterns of PA phase spectrum depend on the ligand and lanthanide ion, and the phase angles are associated with the lifetime of the excited states and the optical absorption coefficient. Different phase angles of the ligand and lanthanide ion bring the possibility to separate their overlapping peaks by PA phase-resolved method. The phase angle of Trp(106 degrees) is calculated according to the in-phase and out-of-phase signals. In the PA amplitude spectrum, only the contribution of Nd3+ can be observed when the phase angle varies 90 degrees. PA peaks of Nd(Trp)3Cl3.H2O are separated well and assigned. PA phase-resolved method has the advantage to interpreted the spectrum based on different phase angles, and is free from the overlapping of different absorption bands.