|GCxGC–HRTOFMS analysis of a complex lipid profile in human sebum
|Comprehensive Chromatography - The State of the Art
|Mr Masahiro Hashimoto
|Mr Kouji Okuda
Dr A. John Dane
Dr Robert B. Cody
Mr Bram van der Meer
Abstract Information :
Skin is an active metabolic tissue that synthesizes a variety of complex lipid compounds. Sebum, an oily material secreted by the skin, is known to provide moisturizing effect, sun light protection, and antibacterial protection for the skin surface. The sebum consists of a complex mixture of free fatty acids, squalene, cholesterol, wax esters, diacylglycerols and triacylglycerols. These species and their concentrations vary depending on skin conditions.
Lipid compounds are generally measured by using GC–FID, GC–MS or LC–MS. However, these methods are often unable to separate all of the individual compounds from each other under the same measurement conditions. In addition, it can be difficult to definitively identify each lipid compound due to coelution.
On the other hand, two-dimensional GC - high resolution time-of-flight mass spectrometry (GCxGC–HRTOFMS) is a powerful tool for identifying analytes in complex mixtures such as crude oils. The purpose of this work is the comprehensive detection and identification of lipid compounds in sebum by using GCxGC–HRTOFMS.
The sample was collected onto square aluminum sheets wiped across a human forehead. The lipid compounds were then extracted from the aluminum sheets using a 50 / 50 volume solution of methanol / dichloromethane with sonication. Next, the extraction solution was centrifuged and concentrated. Afterwards, the final solution was analyzed using GCxGC–HRTOFMS.
The 2D GC conditions resulted in high chromatographic separation of the lipid compounds from low boiling point fatty acids up to high boiling triglycerides in a single measurement. Additionally, these lipid compounds were comprehensively identified using a combination of accurate mass measurements and library searches by HRTOFMS.
As an example, the peaks detected at retention time 18.684 minute (1st column), 6.756 seconds (second column) was matched to oleic acid using an NIST library search. Furthermore, this mass spectrum showed a molecular ion that coincided with the calculated accurate mass of oleic acid (error of 1.4 mDa). The results for the other compounds present in the sebum sample will be presented in this work.