Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

The material comprising the living "organic" share of any ecosystem (leaves, fungi, bark, tissue; Figure 1) differs fundamentally from the material of the non-living "inorganic" share (rocks and their constituent minerals, oxygen, water, metals). Organic material contains carbon linked to a series of other carbon and hydrogen molecules (Figure 2), which distinguishes it from inorganic material. Carbon's wide valency range (-4 to +4) allows it to form up to four separate covalent bonds with neighboring atoms, usually C, H, O, N, S, and P. It can also share up to three covalent bonds with a single other atom, such as the triple bond in the often-poisonous cyanide, or nitrile, group. Over the past 4.6 billion years, this flexibility has led to an amazing array of chemical structures, which vary in size, complexity, polarity, shape, and function. The scientific field of organic geochemistry is concerned with the identification and characterization of the whole range of detectable organic compounds, called biomarkers, produced by life on this planet, as well as others, through geologic time.

Figure 1. Organic material, such as trees, leaves, and moss, are chemically and visually distinct from inorganic material, such as pavement.

1. Collect the Necessary Materials

1. Samples (leaves, dirt, fungi, bark, tissue), usually frozen, freeze-dried, crushed, and homogenized prior to extraction, extracted in groups to maximize efficiency. Extract three samples.
2. Depending on the size of the sample, vials with volumes ranging from 4-60 mL may be used. For this experiment, borosilicate glass vials (40 mL) and solvent safe caps are used. Vials, borosilicate glass pipettes, and weighing tins should be combusted at 550 °C for 6 h pri

At the end of extraction, a total lipid extract (TLE) for each sample is evident. Each vial contains the extractable organic matter from a sediment, soil, or plant tissue. These TLEs can now be analyzed and their chemical constituents identified and quantified.

Different classes of biomarkers impart information on specific aspects of the Earth system. For example, in its infancy, organic geochemistry was primarily concerned with the formation, migration, and alteration of petroleum, and many of the chemical tools organic geochemists use today are based on those initial investigations. It was through the investigation of a class of compounds called isoprenoids, having a repeating five carbon pattern (Figure 2), that scientists discovered petroleum comprised the