Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

Every lab needs standards that track the performance, accuracy, and precision of its instruments over time to ensure a measurement made today is the same as a measurement made a year from now (Figure 1). Because standards must test the performance of instruments over a long period of time, large volumes of the standards are often required. Many chemical standards can be purchased from retail scientific companies, like Sigma-Aldrich and Fisher. However, some compounds that occur in nature and that are relevant to paleoclimatic studies have not yet been isolated and purified for purchase. Therefore, these compounds need to be extracted from natural samples, and because of the large volumes of standards required, large volumes of sediment need to be extracted. The Accelerated Solvent Extraction (Dionex) and sonication extractions are not appropriate for the extraction of such large sediment volumes. In these circumstances, a Soxhlet extraction is used.

Figure 1. Schematic depicting how chemical standard tracks the performance of an instrument through time. The dashed line represents a 1:1 relationship between the accepted and measured (on the instrument) value of a variable. Each star is a weekly measurement of the chemical standard. Green stars represent standards that are accurate. Red stars reflect those that are not accurate indicating that the instrument requires corrective maintenance.

1. Setup and Preparation of Materials

1. Collect a sample of frozen, freeze-dried, crushed, and homogenized marine sediment. A sample like this contains many of the compounds needed for standards.
   1. Standards are often made from sediments that are left over after a coring expedition or analysis. For example, in this experiment, sediment that was obtained from the 'Mud Patch' located just south of Cape Cod is extracted. This sediment was taken as part of a coring expedition but will not be used

At the end of extraction, a total lipid extract (TLE) for the sample is produced. The round-bottomed flask contains the extractable organic matter from the sediment sample. This TLE can now be analyzed, and its chemical constituents identified and quantified.

The extract from the marine mud contains compounds called alkenones, which are used in paleoceanography. Alkenones are long-chained alkyl-ketones produced by certain classes of haptophyte algae that live in the sunlit surface ocean³ (Figure 3). The two most common alkenones are 37 carbon atoms long and have two or three double bonds in them. The haptophytes adjust the ratio of these two alkenones in their cells according to the temperature of the water they live in. The ratio of the two a

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