• Rearranged
NEW MICROWAVE DIGESTION BOMBS
100
aa20R 50
/3/320S
I ^i_
AfjjjU 70
75
80 Time (min)
85
90
Figure 3. Sterane distributions in crude oils determined by single ion monitoring of /77/Z217. The resulting distribution consists of regular and rearranged steranes, some of which have similar retention times. The stereochemistry of the C29 steranes is shown on the peaks corresponding to these isomers.
PAT. PENDING
Now in two sizes, 23 ml and 45 ml. The speed and convenience of microwave heating can now be applied to the digestion of inorganic, organic, or biological materials in a Teflon Lined Bomb. The new Parr Microwave Digestion Bombs have been designed to combine the advan tages of closed high-pressure and high temperature digestion with the requirements of microwave heating. Many samples can be dissolved or digested with less than one minute heating times. As with all Parr Digestion Vessels, careful design and test ing effort have gone into the safety and sealing aspects of this unique vessel and operating environment. Call or write for Bulletin 4781 with complete technical details.
high concentrations of C29 sterols that will give C29 steranes. (Recent work, however, has shown that certain algae also contain abundant C29 sterols.) The ratio of the C27/C29 steranes has been used to indicate the relative amount of marine vs. higher plant source material present in a particular sample. In cer tain cases, specific steranes have been associated with a particular class of or ganism. For example, dinoflagellates contain an abundance of 4-methylsterols, which will produce 4-methylsteranes. Steranes possess a number of carbon atoms at which the configuration of the
hydrogen atom can change as the ma turity of the samples changes. Most sterols have a Δ5 double bond which, as a result of early diagenetic reduction, will lead to stands and steranes with a 5a(H)/5!S(H) ratio that is usually great er than 3 to 1. This ratio will increase even further as maturity increases, leading to a dominance of the 5a(H) configuration. The stereochemistry of the hydrogen atoms at C14 and C17 also changes from the 14α(Η), 17α(Η), or aa configuration to the ββ configura tion with increasing maturity. The 20/? configuration, present in naturally oc curring sterols, is transformed to 20S
Pentacyclics
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