Solid-phase microextraction basics

The time required for quantification of volatiles by both the Basic Protocol and the Alternate Protocol depends on the isolation/extrac-tion procedure chosen. A complete homogenization of the labeled standards with the sample usually requires not more than 30 min and GC-MS analysis is accomplished within 1 hr. In combination with a high-throughput method like solid-phase microextraction, the GC cycle times (-1 hr) become the limiting factor in the quantification of multiple samples by IDAs. 

Solid phase microextraction (SPME) represents a modem alternative for sample preparation eliminating most of the disadvantages related to water sample preparation, SPME is a new sample enrichment technique that can easily transfer the analytes to the GC inlet. Since the invention of the technique in 1989 by J. Pawliszyn, its applications have dramatically increased. It has been used mainly for environmental water analysis (Pawliszyn, 1997). The basic equipment of SPME is simple. As shown in Fig. 4, a fiised-silica rod is connected to a stainless steel tube that can be withdrawn inside a syringe needle, after sampling, for protection and transfer to GC inlets. 

The newly developed solid-phase microextraction (SPME) technique, first reported by Pawliszyn in 1989, is increasingly used for the gas chromatographic determination of a wide variety of volatile and semivolatile organic compounds in water or aqueous extracts of different substrates. Basically, it involves the extraction of specific organic analytes directly from aqueous samples or from the headspace of these samples in closed vials. The extraction is achieved onto a fused-silica fiber coated with a polymeric liquid phase. After equilibration, the fiber containing the absorbed or adsorbed analyte is removed and thermally desorbed in the hot injector port of a gas chromatograph or in an appropriate interface of a liquid chromatograph. ... 

The quest for new suitable materials represents a similar trend in the development of the solid-phase microextraction (SPME) techniques. Polypyrrole and poly N-phenylpyrrole films exhibit better selectivity toward polar, aromatic, and basic pesticides, due to their inherent multifunctional properties. Their high surface areas (also revealed by scanning electron microscopy) are responsible for the high extraction efficiencies shown by these materials. Mixtures of divinyl-benzene, carboxen, and polydimethylsiloxane-based... 

While open tubular (OT) columns are the most popular type, both open tubular and packed columns are treated throughout, and their advantages, disadvantages, and applications are contrasted. In addition, special chapters are devoted to each type of column. Chapter 2 introduces the basic instrumentation and Chapter 7 elaborates on detectors. Other chapters cover stationary phases (Chapter 4), qualitative and quantitative analysis (Chapter 8), programmed temperature (Chapter 9), and troubleshooting (Chapter 11). Chapter 10 briefly covers the important special topics of GC-MS, derivatization, chiral analysis, headspace sampling, and solid phase microextraction (SPME) for GC analysis. 

Fan, Y. Feng, Y. Da, S. Shi, Z. Poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary for in-tube solid phase microextraction coupled to high performance liquid chromatography and its application to determination of basic drugs in human serum. Analyriica Chimica Acta 2004, 523, 251-258. 

Solid phase microextraction (SPME) was introduced by Arthur and Pawliszyn over 20 years ago [44]. It is a straightforward, solvent-free, and fast sample extraction method. SPME has become a widely used technique in many areas of analytical chemistry, such as food analysis, environmental sampling, forensics/toxicology, and biological analysis. Recent reviews have been published showing the latest development of this versatile extraction method [45 8]. SPME is based on the partition of the analyte between the extraction phase and the matrix. The technique can be used to monitor analytes in liquid samples or in the headspace and is basically compatible with HPLC and CE, but most applications are made by GC. As indicated by its name, it is not an exhaustive extraction technique and only a fraction of the target analyte is actually extracted. The quantity of analyte extracted is proportional to its concentration, as long as the equilibrium between the analyte in the fiber and the sample is reached. It provides linear results for wide concentrations of analytes (typically from levels of parts per million to parts per billion). 

Some of the newer procedures use the same basic principles as the older extraction methods but provide fast and easy-to-use options and generally consume less organic solvent. For the most part, they have higher initial purchase price than the traditional methods. Examples include supercritical fluid extraction, accelerated solvent extraction, and automated solid-phase extraction and microextraction. Modular systems are now readily available that automate these proce-... 

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