SPME Samples

Extraction occurs when the needle of the syringe is exposed to fast moving, hot streams of gas within the injection port of the gas chromatograph [55]. 

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The main characteristics of on-line SPME-GC coupling are given in Table 7.10. Although the SPME sampling regime itself (room-temperature operations) is not harsh, other parts of the analytical system (such as the... 

Twenty-five archaeological samples from ancient Egypt were also analysed with the PDMS fibre, at 80°C, over 1 h [25], The samples were from the collections of the Guimet Museum in Lyon and are either balms sampled on different mummies or oils or unguents found in containers inside tombs. The best results were obtained when the samples were compact materials able to be ground just before SPME sampling. The five following examples are taken from the literature [25]. 

A. Keszler, K. Heberger, Influence of extraction parameters and medium on efficiency of SPME sampling in analysis of aliphatic aldehydes, J. Chromatogr. A, 845, 337 347 (1999). 

M. E. Miller, J. D. Stuart, Comparison of gas sampled and SPME sampled static headspace for the determination of volatile flavor components, Anal. Chem., 71, 23 27 (1999). 

Fig. 6.12 Chromatogram repeatability test (a) separation between toluene and decane (b) separation between decane and DMMP and (c) separation between decane and dodecane. The insets in parts (a) and (b) are the chromatogram for each individual gas component. Variation in peak height is due to the variations in SPME sampling time. Curves are sifted vertically for clarity. Reprinted from Ref. 27 with permission. 2008 American Chemical Society...

Solid-Phase Micro extraction (SPME) Sampling... 

The volume of standard added should be kept to a minimum if headspace sampling or SPME sampling is performed. For extraction work-up procedures, the amount of solvent added via the standard may not be critical at all. 

GC combined with mass spectroscopic (MS) detection provides very accurate identification and quantification of FFAs. Pinho et al. (2003) monitored changes in the FFA content during the ripening of ewe cheese. Sampling was done by headspace solid-phase microextraction (SPME). An excellent correlation was observed between the initial concentration of the sample and the amount absorbed on the SPME fiber. SPME sampling was done at 65 °C with a fiber coated with 85-p.m polyacrylate film. After equilibration at 65 °C for 40 min, the fiber was exposed to the sample headspace for 20 min and inserted into the GC port. Despite its accuracy, the GC-MS method is not widely used, presumably because of its cost and complexity. 

The following table provides the temperature dependence of the saturated vapor pressure and vapor density of water. This information is useful in gas chromatographic headspace analysis and for SPME sampling.12... 

SolidPhase Microextraction - SPME), sampling the analytes directly from the medium of interest (gas, liquid)... 

One of the major advantages of SPME is that it is a solventless sample preparation procedure, so solvent disposal is eliminated [68,131], SPME is a relatively simple, straightforward procedure involving only sorption and desorption [132], SPME is compatible with chromatographic analytical systems, and the process is easily automated [131,133], SPME sampling devices are portable, thereby enabling their use in field monitoring. 

SPME can be used to extract semivolatile organics from environmental waters and biological matrices as long as the sample is relatively clean. Extraction of semivolatile organic compounds by SPME from dirty matrices is more difficult [134], One strategy for analyzing semivolatiles from dirty matrices is to heat the sample to drive the compound into the sample head-space for SPME sampling another approach is to rinse the fiber to remove nonvolatile compounds before analysis [134],... 

An effective combination of FMAE and SPME to enhance selectivity for the quantitative GG analysis of cocaine in leaves of E. coca has been proposed by Bieri et al. [38]. The dual extraction step greatly improved the selectivity, thus allowing much faster GG-EID analysis. Einally, by optimizing the desorption step after SPME sampling and by using a fast GG method, Ilias et al. [37] were able to complete a quantitative cocaine analysis from coca leaves (i.e. sample preparation, extraction, and chromatography) in less than Ih (Eigure 12.3). 

The speed of extraction is controlled by the mass transport of the analytes from the sample matrix to the coating. This process involves convective transport in an air or liquid sample, desorption of the analytes from the solid surface when particulate matter is present, and diffusion of the analytes in the coating [205], In direct SPME sampling, the mass transfer rate is determined by the diffusion of analytes in the coating provided the sample matrix is thoroughly agitated. 

Optimisation of Headspace Solid Phase Microextraction (HS-SPME) sampling for GC-MS analysis of CFSV compounds... 

Microextraction (HS-SPME) Sampling for GC-MS Analysis of Tropical Fruit Scenting Sulphur Volatiles (TFSV) Compounds... 

Commercial SPME sampling devices have a number of inherent problems when deployed in a hostile sampling environment ... 

Using SPME fibers and SPME sampling chambers in the sampling and preconcentration steps has several advantages over the methods described before ... 

Keszler, A., Heberger, K., and Gude, M. 1998. A quantitative analysis of aliphatic aldehydes by headspace SPME sampling and ion-trap GC-MS, Chromatographia, 48, 127. 

Unlike solvent extraction, the entire amount of analyte is not extracted. The amount of analyte extracted by the coated fiber is proportional to the concentration of analyte in the sample. This will be true if equilibrium between the fiber and the sample is achieved or before equilibrium is achieved if the sampling conditions are controlled carefully. SPME sampling and desorption can be used for qualitative and quantitative analyses. 

SPME sampling is used for a wide variety of analytes, including environmental pollutants, volatiles from botanical samples (e.g., used to identify tobacco species). 

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