Development of a QuEChERS-based method combined with gas chromatography-mass spectrometry for the analysis of alkanes in sediments

We present a new method based on the QuEChERS protocol (Quick, Easy, Cheap, Effective, Rugged, and Safe) for the determination of 29 n-alkanes (C-12-C-40) and two isoprenoid acyclic hydrocarbons (pristane and phytane) in sediments using gas chromatography-mass spectrometry for their separation and determination. Different factors affecting the extraction efficiency of these lipid biomarkers (such as type of extraction solvent, water addition proportion and timing, agitation mode, and type and amount of clean-up sorbent) were optimized by means of a step-by-step approach. The methodology was validated in terms of matrix-matched calibration, detection and quantification limits, and recovery using 5-alpha-androstane as internal standard. Calibration curve determination coefficients were higher than 0.9902 while relative recovery values varied in the range 60-117% for alkanes C-20-C-40, C-14, C-16, and C-18 and 34-69% for C-12, C-13, C-15, C-17, C-19, pristane, and phytane, with relative standard deviation values below 20%. The method's quantification limits ranged between 2.2 and 37.9 ng/g. Finally, five sediment samples from the Neanderthal site of El Salt (Alicante, Spain) were analyzed using the new method, yielding alkanes C-22 to C-34 with odd to even predominance and C-16 to C-33. This paper represents the first application of QuEChERS for the extraction of alkanes and the analysis of archaeological or geochemical samples