Extending the Limits of Solid Phase Microextraction

Solid phase microextraction (SPME) is a solventless extraction technique that combines sample preparation and sample introduction into a gas chromatograph into a single step. For the past 20 years, solid-phase micro-extraction (SPME) has been used in numerous fields such as: food analysis, including juices, alcohols fruits and vegetables for volatiles, aroma, caffeine, fatty esters, environmental applications including volatile organic contaminants, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phenols, pesticides, steroids, herbicides, acid/neutral/base compounds, and organometallic compounds from water, air, soil, sludge, and sediment samples and in biomedical analysis. This work demonstrates the extension of the limitations of SPME with respect to extraction and analysis of a) extension of headspace SPME to larger polycyclic aromatic hydrocarbons from fish oil b) less volatility analytes, combination of SPME-Gas Chromatograph –Mass Spectrometer –Mass Spectrometer (SPME-GC-MS-MS) to achieve lowered detection limits with steroids in water and c) and highly selective detection of fatty acid methyl esters in olive oil. Headspace solid-phase microextraction (HS-SPME) was used in combination with gas chromatography-mass spectrometry (GC-MS) to screen standards of polycyclic aromatic hydrocarbons (PAH) at part per billion levels and to detect and quantify PAHs in fish oil. Samples from menhaden fish were collected in 2010 to study the effect of Gulf of Mexico oil spill on marine life. The method presented a linear range from 50-1500 ng/g, with precision lower than 10% RSD. The limit of detection and quantification varied from 0.1 to 50 ng/g. Naphthalene, fluorene, fluoranthene, pyrene, anthracene were detected in real samples. The concentrations of PAH’s detected in the real samples were well below the limits given by the FDA. This is the first demonstration of the use of HS-SPME to detect larger PAHs such as benzo(a)pyrene in a complex matrix. Direct immersion SPME-GC-MS-MS was used for the analysis of steroids in water at part-per-trillion (ppt) and lower concentrations. The method was validated and extended to real sample analysis. The method was linear from 0.01 to 5 ng/mL with precision less than 10% relative standard deviation for a steroid mixture at 1 ng/mL. Limits of quantitation and limit of detection was found to be 200- 1200 pg/L and 30-200 pg/L respectively and recoveries ranged from 88-103 %. To understand the extraction efficiency of the fiber, a depletion study was performed. The fiber/ sample partition coefficients for the steroids were determined to be 1.0x104 to 1.5x 104. The extraction was performed without derivatization or the use of an internal standard. This work demonstrated both reduced the detection limits (parts per quadrillion, ppq) and quantitative analysis of steroids without derivatization or use of an internal standard. For the analysis of fatty acid methyl esters (FAMES) in olive oil, headspace SPME was used, followed by GC–MS-MS with a traditional DB-5 (95% dimethyl polysiloxane and 5 % biphenyl) column. A 37 component FAME mixture was used as standard mixture. Since FAMES are polar analytes, a polar fiber Car/PDMS/DVB (50/30 µm) fiber was used for the extraction. The product scan and multiple reaction monitoring (MRM) mode of MS-MS were used for the analysis. The selectivity provided by the GC-MS-MS detector demonstrated separation of the polar fatty acid methyl esters on a non- polar column. This work demonstrated several extensions of SPME with GC-MS. HS-SPME is demonstrated to be effective for analysis of larger PAH not normally analysed using headspace technique. With GC-MS-MS, SPME was extended to part per quadrillion analysis of steroids, without requiring internal standards or derivatization for effective quantitation. The use of selective detection by MS-MS allows the quantitation of polar FAMES on a traditional non polar column. Further all of the work in this research, although the analytes were disparate: steroids, polycyclic aromatic hydrocarbons, fatty acid methyl esters, was performed using a single non polar stationary phase: 5% phenyl polydimethylsiloxane (DB-5) and column dimensions: 15m x 0.25mm x 0.25 µ