Soret band porphyrin structure index via 3rd derivative UV/VIS spectroscopy

This paper reports on Soret band wavelength which provides a porphyrin structure index which is useful to classify natural metalloporphyrin extracts. The approach involves rapid measurement by photodiode array spectrophotometry. The average value for a porphyrin mixture. λSoret ± 0.1 nm, is obtained by third derivative computation. A blue shift in λSoret implies an increasing etio to exocycle ratio. High ratios have been associated with catagenesis (Dydik, 1975, Baker, et al., 1978, 1983), and with predispositional generation (Baker and Louda (1984). As a reference, we measured the Soret band response to simulated maturation of a Woodford Shale (350 Ma) sample after hydrous pyrolysis (Lewan, 1981), as described in greater detail elsewhere at this meeting