Elucidation of aquatic humic partial structures by multistage ultrafiltration and two-dimensional nuclear magnetic resonance spectrometry

An on-line wavelet transform (WT) algorithm was proposed and successfully used in processing the photoacoustic (PA) signal. By investigating the spectra of three rare earth compounds, it was indicated that after on-line decomposition by WT, the noise in the PA spectra was cleanly removed, and the resolved information in the overlapping peaks was easily retrieved. The effect of different sampling rate on resolved results was also investigated. The experimental results showed that the position of peaks after decomposition agreed with the corresponding intramolecular energy transition bands, which demonstrated that WT is a useful and efficient tool for the study of energy bands of rare earth compounds using PA spectroscopy. Received: 7 July 1998 / Accepted: 14 September 1998