Study On The Analytical Method Of Lipid Biomarkers In Marine Sediments

Lipid biomarkers can provide the important reference information about the source of organic matter, distribution and deposition law in marine sediments, as well as the ancient marine environment. The paper described the determination of n-alkanes, fatty alcohols and fatty acids in marine sediments by gas chromatography mass spectrometry with accelerated solvent extraction(ASE) for sample pretreatment. The main factors which affect the extraction yield of n-alkanes, fatty alcohols and fatty acids by ASE, such as the proportion of extractant, the temperature, static time and cycle times were discussed. The following conclusions from the study: when the long carbon chain n-alkanes to be detected or be higher in samples, we recommend using methanol-methylene chloride(V:V, 1:3) as the extraction solvent while the short carbon chain n-alkanes to be detected or be higher in samples, we recommend using methanol-methylene chloride(V:V, 1:9) as the extraction solvent; the quantity of short and long carbon chain n-alkanes and the total n-alkanes gradually increases with the increasing of the temperature, static time and number of cycles. The optimum parameters for n-alkanes extraction from marine sediments were: temperature of 150℃, static time of 15 min and 3 cycles. The precision of method was 3% to 14% RSD. Alternatives recovery was 84-114%. The optimum conditions of fatty alcohol: the quantity of short and long carbon straight-chain alcohols and the total straight-chain alcohols gradually increases with the increasing of the temperature, static time and number of cycles. The optimum parameters for straight-chain alcohols extraction from marine sediments are: the extractant of methanol-methylene chloride(V: V, 1:3), temperature of 150℃, static time of 15 min and 3 cycles. The precision of method is from 3% to 17%(n=5), the recovery is 77.5% to 117.1%. The optimum conditions of fatty acids: For the conditions of the extraction temperature and static extraction time, different types of fatty acids vary regularly presented. The method to extract the fatty acids to maximize(highest extraction efficiency) as the basis to optimize the optimal experimental conditions: temperature of 110℃, static time of 10 min and 3 cycles. The precision of method was 3% to 23% RSD. This method is simple, fast, efficient and having high recovery and good precision, which is applicable to the quantitative analysis of straight-chain alcohols in marine sediment. We studied the methods of separation and purification of n-alkanes, aromatic hydrocarbons and alcohols in the marine sediments by SiO2/C3-CN(1g/0.5g, 6mL) and NH2(0.5g, 3m L) solid phase extraction column. The results showed that: SiO2/C3-CN(1g/0.5g, 6mL) solid phase extraction column with 4.5mL hexane and 4.5mL hexane-methylene chloride(V: V, 1: 1) can completely elute and separate n-alkanes and aromatics, the recovery of n-alkanes was 98.1%, while the low number of rings of aromatic compounds and n-alkanes are eluted in the fraction of hexane. NH2 solid phase extraction column with 3mL hexane-methylene chloride(V: V, 1: 1) and 4m L dichloromethane-methanol(V: V, 1: 1) can elute completely and separate aromatics and alcohols, the recovery of alcohols was 112.3%, while high number of rings of aromatics and alcohols were together eluted in dichloromethane-methanol fraction. The use of SiO2/C3-CN and NH2 solid phase extraction column to do actual sample repeatability test, the precision(RSD) were each from 1.0 to 18.1% and from 0.8 to 16.6 percent, And the impurity matrix in the marine sediment samples can be effectively purified. According to different demand of actual determination, those methods can be used in the purification and separation of marine sediments or other complex matrices.