Determination of n-alkanes by Gas Chromatograph-Mass Spectrometry Coupled Solid Phase Microextraction with a New Organic/Inorganic Composite Coating

Concentrations of n-alkanes in water often indicate the degree of organic pollution in a specific region. Trace n-alkanes analysis is often associated with the separation and enrichment process in order to improve the sensitivity and selectivity of the method. The conventional separation and enrichment methods, such as liquid-liquid extraction, are time-consuming and utilize a large quantity of organic solvents. Conversely, the Solid Phase Microextraction (SPME) technology has the characteristics of high efficiency and high sensitivity. A new method of determining 26 n-alkanes by using a homemade organic-inorganic hybrid solid phase microextraction coating combined with Gas Chromatography-Mass Spectrometry (GC-MS) has been established. The homemade SPME coating produced by the sol-gel method has good stability and is matrix resistant. The optimized analytical conditions were 30 min of extraction at 25℃ in immersion extraction mode. Under the optimized conditions of SPME-GC-MS, analysis signals of all 26 n-alkanes had good linear relationships with the concentration. The linear correlation coefficient r ranged from 0.9935 to 0.9999. The detection limits (k=3) were in the range of 0.011 to 0.085 (μg/L), and the relative standard deviations (RSD, n=5) ranged between 3.9% and 10.0%. The results show that the detection limits of 26 n-alkanes with homemade organic-inorganic hybrid coating were 2-10 times lower than the commercial PDMS coating, and more types of n-alkane were simultaneously determined with high sensitivity. The method is simple, fast, sensitive and easy to use in the determination of n-alkanes. The homemade organic-inorganic hybrid SPME coating shows excellent performance of n-alkanes analysis and potential applications.