Abstract
Wax esters (ranging from C
32 to C
44), very long mid-chain ketones (ranging from C
31 to C
43) and sterol ethers were isolated from Walvis Bay diatomaceous ooze and identified by glass capillary gas chromatography/mass spectrometry and direct probe high-resolution mass spectrometry.
The wax ester compositions of co-eluting wax esters with the same molecular weight were determined from fragment ions characteristic for the alcohol and fatty acid moieties. Dominant wax esters are the C
3(16F-20A), C
36(18F-18A), C
38(16F-22A), C
38(18F-20A), C
40(18F-22A), C
40(20F-20A) and C
40(24F-16A).
The presence of isoprenoid wax esters and the chain length distributions of alcohol and fatty acid moieties point to an origin from zooplankton. The position of the ketogroup in the mid-chain ketones is determined from characteristic fragment ions. Major ketones are the C
38(C
18H
37-CO-C
19H
39) and C
40(C
18H
37-CO-C
21H
43).
The sterol ethers have C
8 and C
9 ether moieties and C
27, C
28, and C
29 steroid moieties. The origin and significance of the ketones and the sterol ethers is obscure.