Disk-based solid-phase extraction

M. Miro, W. Frenzel, J.M. Estela, V. Cerda, A novel flow-through disk-based solid-phase extraction diffuse reflectance optrode. Application to preconcentration and determination of trace levels of nitrite, Analyst 126 (2001) 1740. 

M. Mir6, W. Frenzel, V. Cerda, J.M. Estela, Determination of ultratraces of nitrite by solid-phase preconcentration using a novel flow-through spectrophotometric optrode. Anal. Chim. Acta 437 (2001) 55—65. M. Mir6, W. Frenzel, J.M. Estela, V. Cerda, A novel flow-through disk-based solid-phase extraction diffuse reflectance optrode. Application to preconcentration and determination of trace levels of nitrite. Analyst 126 (2001) 1740-1746. 

Alternative 2. By hyphenating an optical fiber sensor for implementing disk-based solid-phase extraction and direct optosensing at the solid surface, there is no need for further elution to perform the optical detection in the eluate phase, as demanded in conventional sorbent-extraction protocols previously reported for sulfide, thus yielding improved enrichment factors [14] (Figure 7.5). 

Off-hne solid-phase extraction (SPE) procednres, based on cartridges, Empore disks, or ZipTip procednres, are freqnently apphed for clean-np of peptide mixtures prior to ESI-MS or LC-MS analysis. This was evalnated by Erdjnment-Bromageeia/. [23]. 

Solid-phase extraction (SPE) is a procedure in which an analyte, contained in a liquid phase, comes in contact with a solid phase (sorbent particles in a column or disk) and is selectively attracted to the surface of that solid phase. All other materials not adsorbed by chemical attraction or affinity remain in the liquid phase and go to waste. A wash solution is then usually passed through the sorbent bed to remove any loosely adsorbed contaminants from the sample matrix, yet retain the analyte of interest on the solid phase. Einally, an eluting solvent (usually an organic solvent such as methanol or acetonitrile that may be modified with acid or base) is added to the sorbent bed. This solvent disrupts the attraction between the analyte and solid phase that cause desorption,... 

One recent application in lEC consists of solid phase extraction disks which are used to eliminate matrix interference prior to analysis. The disk contains a membrane composed of resin beads enmeshed in a PTFE membrane, housed in a polypropylene housing. The resin is treated to remove specific ions such as H+ to remove hydroxide, Ag+ for excess halides and Ba to remove sulphate. Other disks such as hydroxide for acid removal and neutral styrene-divinylbenzene to eliminate hydrophobic components which can damage resin based IC columns are being developed [23]. 

Shamsipur, M. Ghiasvand, A.R. Sharghi, H. Naeimi, N. Solid phase extraction of ultra trace copper(lI) using octa-decyl sihca membrane disks modified by a naphthol-derivative Schiff s base. Anal. Chim. Acta 2000, 408, 271. 

Solid-phase extraction is a relatively new sample preparation method based on chemically modified silica gel or other sorbent type packed into a small plastic disposable cartridge or column. The cartridges are usually coimected to the end of a syringe and samples passed through by pressure, and the columns and disks are normally used in a vacuum manifold. Sorbents with various functional groups can be obtained in different configurations and sizes from commercial suppliers, which can supply procedures for analyses and bibliographies of applications. 

SPME was developed by Pawlisz)m and coworkers in 1987 [161-163]. The reader may find further information on the historical evolution, principles, and commercially available devices of SPME in an excellent review by the pioneer of the technique [164]. SPME is based on a partitioning equilibrium of the solutes between the sorbent phase and the aqueous and/or gas matrix. A small amount of sorbent phase is dispersed on a solid support, which will be exposed to the sample for a predetermined time. Different implementations were developed such as suspended particles, coated-stirrer, vessel walls, disks, stirrers, or membranes, although the fiber and in-tube are explored theoretically and experimentally in depth. The former consists of a thin, fused-silica fiber-coated with sorbent on its surface and mounted in a modified GC syringe, which protects the fiber and allows handling. The latter in-tube implementation consists of an internally coated tube or capillary. The analytes are extracted by sorption when either coated fiber or tube are immersed in the water sample (direct SPME) or in the headspace above the sample (HS-SPME). 

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