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Solid-phase extraction, with desorption/injection

Principles and Characteristics As mentioned already (Section 3.5.2) solid-phase microextraction involves the use of a micro-fibre which is exposed to the analyte(s) for a prespecified time. GC-MS is an ideal detector after SPME extraction/injection for both qualitative and quantitative analysis. For SPME-GC analysis, the fibre is forced into the chromatography capillary injector, where the entire extraction is desorbed. A high linear flow-rate of the carrier gas along the fibre is essential to ensure complete desorption of the analytes. Because no solvent is injected, and the analytes are rapidly desorbed on to the column, minimum detection limits are improved and resolution is maintained. Online coupling of conventional fibre-based SPME coupled with GC is now becoming routine. Automated SPME takes the sample directly from bottle to gas chromatograph. Split/splitless, on-column and PTV injection are compatible with SPME. SPME can also be used very effectively for sample introduction to fast GC systems, provided that a dedicated injector is used for this purpose [69,70],... [Pg.437]

In the 1990s, Pawliszyn [3] developed a rapid, simple, and solvent-free extraction technique termed solid-phase microextraction. In this technique, a fused-silica fiber is coated with a polymer that allows for fast mass transfer—both in the adsorption and desorption of analytes. SPME coupled with GC/MS has been used to detect explosive residues in seawater and sediments from Hawaii [33]. Various fibers coated with carbowax/divinylbenzene, polydimethylsiloxane/divinylbenzene, and polyacrylate are used. The SPME devices are simply immersed into the water samples. The sediment samples are first sonicated with acetonitrile, evaporated, and reconstituted in water, and then sampled by SPME. The device is then inserted into the injection port of the GC/MS system and the analytes thermally desorbed from the fiber. Various... [Pg.43]

Solid-phase microextraction (SPME). used as a sample introduction technique for high speed gc, utilizes small-diameter fused-silica fibers coated with polymeric stationary phase for sample extraction and concentration. SPME lias been utilized for determination of pollutants in aqueous solution by the adsorption of analyte onto stationary-phase coated fuscd-silica fibers, followed by thermal desorption in the injection system of a capillary gas chromatograph. Full automation can be achieved using an autosampler. [Pg.1626]

Thermal desorption from a solid phase microextraction (SPME) fiber has shown considerable potential for selectively introducing semivolatile chemicals into an IMS. ° The SPME approach is a simple design patterned after the early platinum wire introduction thermal desorption system described. With SPME, semivolatile compounds are extracted by either absorption or adsorption onto a nonvolatile polymeric coating or solid sorbent phase that has been coated onto a small fiber. Normally, the adsorption liber is housed in the needle of a syringe to permit puncture of a sample bottle septum and to protect the fiber from contamination during transfer of the fiber from the sample to the IMS instrument. After the analytes are adsorbed onto the SPME fiber, the fiber is retracted into the needle and then injected in a normal syringe technique such that the fiber is extended into the heated region of the IMS and the analytes are desorbed from the fiber into the clean carrier gas of the IMS. [Pg.53]

Solid-phase microextraction (SPME) is a solvent-free sample preparation technique. The volume of the extraction phase is very small compared to the sample volume. The extraction is not exhaustive, but is based on equilibrium between the sample and the extraction phase, which is located on a fiber. SPME involves an adsorption step of the analyte, from a gas headspace or in a liquid sample (direct immersion), and a desorption step, which often is coupled directly with injection in the analytical system. Although SPME is mainly used in combination with GC, it has also been automated for HPLC. Eigure 9.10 shows a schematic representation of an SPME device. [Pg.178]


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Extract phase

Injection Phase

Phase desorption

Phase extraction

Solid desorption/injection

Solid-phase extraction, with

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