Optimization of Simultaneous Extraction and Detection Methods for n-Alkanes and Polycyclic Aromatic Hydrocarbons in Marine Sediments

N-alkanes and polycyclic aromatic hydrocarbons serve as key molecular indicators for reconstructing marine paleoclimate, tracing organic matter sources, and evaluating anthropogenic pollution. Current literature still employs separate pretreatment and detection methods for these two substance categories. For co-extraction, highly polar mixed solvents such as chloroform-methanol or chloroform-acetone are typically used, resulting in numerous co-extracted impurities that reduce quantitative accuracy. Our study employed n-hexane-acetone (4∶1) as the extraction solvent with lower polarity. This approach minimized co-extracted impurities while ensuring recovery rates of all components, thereby enhancing detection accuracy. GC-MS effectively separated all 53 compounds under the same temperature program, with a total detection time of only 80 min. A new method was established for the simultaneous extraction and detection of 53 compounds in marine sediments, encompassing 34 n-alkanes and 16 polycyclic aromatic hydrocarbons (PAHs), along with PAH surrogates including naphthalene-D₈, anthracene-D₁₀, and p-tritylbenzene-D₁₄. Methodological evaluation results indicate that 53 compounds exhibit good linearity within the range of 10 ng/mL to 20 μg/mL, with correlation coefficients exceeding 0.999. The detection limits for n-alkanes range from 0.04 to 1.35 ng/g, while the quantification limits range from 0.16 to 5.40 ng/g. For polycyclic aromatic hydrocarbons, the detection limits ranged from 0.14 to 0.43 ng/g, with quantification limits from 0.56 to 1.72 ng/g. At three spiking levels (1×, 2×, and 8× the QL), recovery rates for target compounds ranged from 60% to 130%, with relative standard deviations (RSD) ranging from 0.22% to 7.04% (n = 6). The detection limits and quantification limits for both substance categories were below standard method requirements, and recovery rates met standard criteria. This work is applicable for the simultaneous extraction and detection of n-alkanes and polycyclic aromatic hydrocarbons in marine sediments.