The main objective of this study is to present the chromatograms and mass spectra of aldehydes so that geochemists could easily identify these compounds in sediment samples. Aldehydes are rare compounds found in the s...The main objective of this study is to present the chromatograms and mass spectra of aldehydes so that geochemists could easily identify these compounds in sediment samples. Aldehydes are rare compounds found in the surface environment, particularly in sediments. To date, aldehydes have not been used as environmental proxies. In this study, long-chain aldehydes detected from coral collected from the east coast of Kenya are analyzed by gas chromatography mass spectrometry (GC/MS) using the typical procedure for biomarker analysis. The retention time of the long-chain aldehydes and fatty acid methyl esters slightly overlapped. Hence, the peak corresponding to the aldehyde in the GC chromatogram is buried with that corresponding to the ester, possibly overlooking the aldehyde. After assessing the difference in the retention time between the aldehydes and fatty acids methyl ester, the aldehydes were easily detected using the standard analytical procedure for biomarkers analysis. A molecular ion (M+) with greater than 23 carbon atoms was detected from long-chain aldehydes. The base peak was observed at m/z 82 in the mass spectra of the aldehyde, where characteristic 68 + 14n ions corresponding to even-numbered ions were observed. The M-18 ion, which was formed by the loss of H2O, as well as M-46 or M-84 ions, was characteristic ions observed for long-chain aldehydes of the number of all carbon. The results obtained from this work, in which aldehydes were identified from coral samples, represent a good example of what could be achieved by geochemists when working with sediment samples and using aldehydes as environmental proxies.展开更多
文摘The main objective of this study is to present the chromatograms and mass spectra of aldehydes so that geochemists could easily identify these compounds in sediment samples. Aldehydes are rare compounds found in the surface environment, particularly in sediments. To date, aldehydes have not been used as environmental proxies. In this study, long-chain aldehydes detected from coral collected from the east coast of Kenya are analyzed by gas chromatography mass spectrometry (GC/MS) using the typical procedure for biomarker analysis. The retention time of the long-chain aldehydes and fatty acid methyl esters slightly overlapped. Hence, the peak corresponding to the aldehyde in the GC chromatogram is buried with that corresponding to the ester, possibly overlooking the aldehyde. After assessing the difference in the retention time between the aldehydes and fatty acids methyl ester, the aldehydes were easily detected using the standard analytical procedure for biomarkers analysis. A molecular ion (M+) with greater than 23 carbon atoms was detected from long-chain aldehydes. The base peak was observed at m/z 82 in the mass spectra of the aldehyde, where characteristic 68 + 14n ions corresponding to even-numbered ions were observed. The M-18 ion, which was formed by the loss of H2O, as well as M-46 or M-84 ions, was characteristic ions observed for long-chain aldehydes of the number of all carbon. The results obtained from this work, in which aldehydes were identified from coral samples, represent a good example of what could be achieved by geochemists when working with sediment samples and using aldehydes as environmental proxies.
