Solid SPME-HPLC

GC injection port) may well be. This was clearly demonstrated by a comparison between cryotrapping/direct injection, cryotrapping/SPME, and solid-phase (Tenax-GC) extraction for sampling of odorous sulfur compounds [71], Thermally labile compounds are likely to break down in the GC injection port/column/transfer line. Instead of SPME-GC, the recently developed SPME-HPLC [72] might be more applicable to analysis of such thermally unstable compounds. 

Aulakh, J.S., A.K. Mailk, V. Kaur, et al. 2005. A review on solid phase micro extraction—High performance liquid chromatography (SPME-HPLC) analysis of pesticides. Crit. Rev. Anal. Chem. 35 71-85. 

SPME can either be performed by head-space extraction (HS-SPME) by placing the fiber in the vapour above a gaseous, liquid or solid sample, or by direct immersion extraction (DI-SPME), by immersing the fiber in a liquid sample. After a certain extraction time, the SPME needle is removed from the septum and inserted into the injection port of the GC or into the desorption chamber of the SPME-HPLC interface. The desorption is performed by heating the fiber in the GC inlet, or by pumping a solvent through the desorption chamber of the SPME-HPLC interface. The main advantages of SPME compared to LLE and solid phase extraction (SPE) are that no or little solvent is... 

A solventless technique of solid-phase microextraction (SPME) has been also employed for HPLC determination of MC in a natural Microcystins sp. bloom in a freshwater, where three dominant MC variants MC-LR, -YR, and -RR were quantified. For this purpose a measuring system with commercial SPME-HPLC interface was employed. Microcystins were sorbed from acidified solutions using SPME fibers with carbowax/templated resin and polydi-methylsiloxane/divinylbenzene coating and desorbed at dynamic mode with HPLC eluent, which was used in isocratic elution mode and consisted of water and methanol with 0.05% TFA. For each toxin partition equilibrium was achieved within 60 min and example response obtained in SPME-HPLC system is shown in Fig. 6. The detection limits for all examined MC for 5 ml samples were reported at about 7 ppb. 

HPLC solvents (PDMS-coated fibres are incompatible with hexane). PDMS fibres are more selective towards nonpolar compounds and polyacrylate fibres towards polar compounds such as acids, alcohols, phenols and aldehydes. Another feature of SPME fibre selectivity is discrimination towards high-MW volatiles. SPME has successfully been applied to the analysis of both polar and nonpolar analytes from solid, liquid or gas phases. Li and Weber [533] have addressed the issue of selectivity in SPME. 

Diffusive sampler Membrane extraction (MESI) Liquid-liquid extraction (LLE) Solid-phase extraction (SPE) SPE-PTV-GC Solid-phase microextraction (SPME) Headspace GC (SHS, DHS) Large-volume injection (LVI) Coupled HPLC-GC Membrane extraction (MESI) Difficult matrix introduction (DMI) Conventional solvent extraction methods 1 Pressurised solvent extraction methods Headspace GC (SHS, DHS) Thermal desorption (TD, DTD) Pyrolysis (Py) Photolysis Photon extraction (LD) Difficult matrix introduction (DMI)... 

Miniaturisation of scientific instruments, following on from size reduction of electronic devices, has recently been hyped up in analytical chemistry (Tables 10.19 and 10.20). Typical examples of miniaturisation in sample preparation techniques are micro liquid-liquid extraction (in-vial extraction), ambient static headspace and disc cartridge SPE, solid-phase microextraction (SPME) and stir bar sorptive extraction (SBSE). A main driving force for miniaturisation is the possibility to use MS detection. Also, standard laboratory instrumentation such as GC, HPLC [88] and MS is being miniaturised. Miniaturisation of the LC system is compulsory, because the pressure to decrease solvent usage continues. Quite obviously, compact detectors, such as ECD, LIF, UV (and preferably also MS), are welcome. 

A combination of various chromatographic techniques, such as RP-HPLC-DAD, RP-HPLC-MS, solid-phase microextraction (SPME) - GC, was employed for the elucidation... 

Solid-phase microextraction (SPME) is effectively a miniamrised version of SPE. Instead of using a packed cartridge, a rod is typically used, which is coated with the stationary phase. This is dipped into a solution of the analyte and allowed to extract for a pre-determined period of time. After this incubation period, the rod is removed from the solution and may be inserted directly into the injection system of the GC or HPLC. All of these operations can be automated on an autosampler. Clearly, the success of this technique depends intimately on the affinity of the analyte for the stationary phase. Frost, Hussain and Raghani [34] used SPME with GC-FID to measure benzyl chloride and chloroethylmethyl ether (amongst other process impurities) in pharmaceutical preparations. 

Oxidation, as is well known, leads not only to the formation of heavy compounds but also of volatile compounds that are responsible for off-flavors. Usually they are evaluated by capillary GC, through several sampling techniques are available (purge and trap, head space solid phase microextraction (SPME)). Rovellini et al. [26] recently proposed the application of HPLC for identifying... 

Other innovations include PLE, MAE (see Section 1.3.1), and solid-phase microextraction (SPME). SPME is a sampling method applied to GC, HPLC, and CE. It is based on adsorbent- or adsorbent-type fibers and lends itself well to miniaturization. ... 

The fabrication of imprinted monolithic solid-phase microextraction fibres has been developed for the selective extraction and preconcentration of diacetylmorphine and its structural analogues, triazines, bisphenol A, anaesthetics, and antibiotics followed by GC or HPLC analysis [156,163,179,196,197]. In addition, the on-line coupling of the imprinted monolith as a preconcentration column with a conventional analytical column has been proposed for the enrichment and cleanup of environmental and food samples [163]. However, at present, the capacity of the imprinted fibres and thus the degree of recovery of analytes are very variable and obviously need some improvement. For example, the recoveries of triazines after SPME with an imprinted monolith prepared by in situ polymerisation of MAA as... 

The use of automation results in fast, easy, and reliable methods for SPE. There are a number of instruments available for totally automated SPE, as well as automated methods development of SPE, which span the spectrum in cost. In environmental applications, the choices of automation are limited, with only the Autotrace by Tekmar available for large-volume samples (1 L). In the area of on-line SPE-HPLC, nearly all of the workstations for SPE have the option for direct injection into the HPLC. For on-line SPE-GC/MS, there are several instruments and methods available (a modified PROSPEKT, Varian automated SPME, and the Hewlett-Packard solid-phase extraction workstation). For total automation including addition of internal standards, derivatiza-... 

Solid-phase microextraction (SPME) A sample preparation technique that uses a fused silica fibre coated with a polymeric phase to sample either an aqueous solution or the headspace above a sample. Analytes are absorbed by the polymer coating and the SPME fibre is directly transferred to a GC injector or special HPLC injector for desorption and analysis. 

Solid phase micro extraction (SPME) is a widely used extraction technique that was developed by Pawlistyn and co-workers in 1990 (74). SPME uses a fused silica fiber that is coated on the outside with an appropriate stationary phase (a S to 100 pm thick coating of different polymers, e.g. polydimethylsiloxane, PDMS). The small size of the SPME flber and its cylindrical shape enables it to fit inside the needle of a syringe-like device. Target molecules from a gaseous or a liquid sample are extracted and concentrated to the polymeric fiber coating. SPME has been used coupled to GC and GC-MS (75), as well as to HPLC and LC-MS 7ll>). Figure 7 shows a conunercially available SPME device. 

An automated in-tube solid-phase microextraction HPLC method for NNK and several metabolites have been developed by Mullett et al. ° In-tube SPME is an on-line extraction technique where analytes are extracted and concentrated from the sample directly into a coated capillary by repeated draw-eject steps. A tailor-made polypyrrole-coated capillary was used to evaluate their extraction efficiencies for NNK and several metabolites in cell cultures. This automated extraction and analysis method simplified the determination of the tobacco-specific A-nitrosamines, requiring a total sample analysis time of only 30 min. 

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