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Negative-ion liquid chromatographic-mass spectrometric analysis of the pigment composition of the bottom sediment (15–20 cm) of a eutrophic lake revealed the presence of a novel series of chlorophyll transformation products, in which a series of C 27 C 30 sterols and stanols are esterified to a pyrophaeophorbide a nucleus of algal origin. The major components are algal-derived chlorophyll a and b degradation products, and the presence of a bacteriochlorophyll-related phaeophytin indicates the presence of anoxic conditions extending into the photic zone when the sediment was laid down.

The high-performance liquid chromatographic separations, on 3-μm silica, of a variety of free-base alkyl porphyrins of the type isolated from sediments and petroleums, and of a number of their acetylated counterparts, have been compared. Members of pseudohomologous series and structural isomers of both aetioporphyrins and cycloalkano porphyrins are readily separable, although the method appears to be less effective for the separation of positional isomers. Substitution of a β-methyl substituent for a β-hydrogen atom results in an increase in t R , presumably partly as a result of increased basicity. The effect of the introduction of an acetyl substituent is to shorten t R in the cycloalkano components, despite the polarity increase, but to increase t R in the aetio components. The differences in t R are explicable, therefore, in terms of an interplay between basicity and polarity, brought about by changes in the structural features of the substituents. The availability of isolated components for coinjection provides a method for routine studies of the distributions of the components of sediments and petroleums.

Recently developed gas chromatographic—mass spectrometric (GC-MS) and high-performance liquid chromatographic (HPLC) procedures for the analysis of petroporphyrios have been employed in the search for benzoporphyrins in six sediments, a bitumen and a petroleum. In addition, structurally assigned monobenzocycloalkanoporphyrms (benzo-CAPs) isolated from Boscan crude oil (Cretaceous, Venezuela) have been used in a co-chromatographic study of these minor components (ca. 1% of total porphyrins). The petroporphyrins are generally obtained by demetallation of metalloporphyrins from samples representing a variety of geographical locations and ages ranging from Permian (ca. 235 million years) to Palaeocene (ca. 60 million years). The data show that, where the benzo-CAPs were detected, up to 24 components can occur, although the dominant member in each case is the C33 compound. Studies of a chromatographic fraction from Boscan crude oil, enriched in high-carbon-number benzo-CAPs, indicates that the series extends from at least C30 to C38 in this sample. The GC behaviour of the benzo-CAPs as the bis(tert.-butyldimethylsiloxy)Si(IV) [(TBDMSO)2Si(IV)] derivatives is characterised by the high Kovats retention indices (ca. 3900-4300; OV-1 column). Similarly, under normal-phase HPLC conditions, the free-base benzo-CAPs elute after the major alkylporphyrins. HPLC co-chromatography of the free-bases provides a rapid means of identification of the major benzo-CAPs (C32 and C33), while the GC-MS procedure allows more detailed characterisation and quantitation of the benzo-CAP distributions as their (TBDMSO)2Si(IV) derivatives.

A significantly improved method is described for the high resolution high-performance liquid chromatographic analysis of alkyl porphyrins on 3-μm silica. This improvement has been achieved by addition of varying amounts of both acetic acid and pyridine to the mobile phase. The technique is of special value in the analysis of complex mixtures of sedimentary alkyl metalloporphyrins after demetallation, and provides a complementary method to the gas chromatographic-mass spectrometric analysis of the bis-( tert .-butyldimethylsilyl)siloxyporphyrin derivatives.

Computerised capillary gas chormatographic—mass spectrometric analysis of the petroporphyrins [as their bis( tert. -butyldimethylsiloxy)Si(VI) derivatives] of Gilsonite (an Eocene bitumen, Uinta Basin, UT, U.S.A.) has revealed 123 components in the C 26 C 36 carbon number range, demonstrating the complexity of such mixtures. Four structural classes have been recognised: (i) the A class comprising 43 components with alkyl β-pyrrole substituents (formerly aetioporphyrins), (ii) the major A-2 class (one further degree of unsaturation; 57 components) containing compounds bearing an exocyclic ring, (iii) the A-4 class (two further degrees of unsaturation; 13 components), and (iv) the A-6 class (three further degrees of unsaturation; 10 components). Co-chromatography of n -alkanes, allowing computer-aided calculation of Kovats retention indices, has enabled further classification into homologous or pseudo-homologous series. Co-chromatography of derivatised porphyrins of known structure has allowed structural assignment of 9 components; at least 24 other compounds are assumed to be structurally related to these components by extrapolation on Kovats plots.