Solid-phase extraction methodology

The separation method described later in this chapter was gradually developed into its final stage currently used at NCUT by first modifying the ASTM D2007 method, and then developing a miniature version utilizing the SPE (solid phase extraction) methodology that also rendered separation of the olefins. 

The analysis of isoflavones has been discussed by several authors. The extraction of isoflavones from soy products preferably occurs by acid hydrolysis of the glucoside conjugates followed by a (hot) extraction with acidic methanol, ethanol, or acetonitrile. Extraction of isoflavones from biological fluids, such as serum, plasma, urine, and milk usually occurs using solid-phase extraction methodology [95]. 

In recent decades the development of preconcentration steps to be implemented prior to analytical determinations of trace level compounds has been explored in considerable depth. With a view to eliminating or at least minimising the use of organic solvents used in conventional liquid-liquid extraction, other methodologies have been developed, such as membrane extraction, solid-phase extraction, solid-phase microextraction, etc. 

Furthermore, multicomponent reactions can also be performed under fluorous-phase conditions, as shown for the Ugi four-component reaction [96], To improve the efficiency of a recently reported Ugi/de-Boc/cyclization strategy, Zhang and Tempest introduced a fluorous Boc group for amine protection and carried out the Ugi multicomponent condensation under microwave irradiation (Scheme 7.84). The desired fluorous condensation products were easily separated by fluorous solid-phase extraction (F-SPE) and deprotected by treatment with trifluoroacetic acid/tet-rahydrofuran under microwave irradiation. The resulting quinoxalinones were purified by a second F-SPE to furnish the products in excellent purity. This methodology was also applied in a benzimidazole synthesis, employing benzoic acid as a substrate. 

Supercritical fluid extraction Solid phase extraction (SPE) Keypoints Introduction Methodology... 

In contrast to the solid-phase extraction approach, only nonpolar Cig-deriva-tized silica has been used as the sorbent in matrix solid-phase dispersion technique. This technique, which simplifies the overall methodology and removes most of the interfering compounds from milk and tissues, has been successfully applied in the determination of sulfonamides in fish muscle (264-267), bovine and swine muscle (66, 268, 269), and milk (270). 

For the determination of CCA in biological samples, methods not based on LC-MS/MS technology [39, 41-43] and methods that used LC-MS/MS [40, 52] have been reported. Most of the sample extraction methods used liquid-liquid extraction (LLE) technology, since this extraction method is simpler and able to minimize matrix effects. Consequently, LLE methods are considered to provide cleaner samples as compared to solid phase extraction (SPE) methods. Since LC-MS/MS methodology uses nonvolatile solvents or a combination of nonvolatile and volatile solvents, difficulties in the evaporation process and associated interferences when samples are injected onto the system can arise [51]. However, Bahrami as well as Souri [42,43] applied a combination of nonvolatile and volatile solvents in which the nonvolatile solvents were acidic buffers (pH 5 or less). Analytes eluted from SPE prepared samples did not undergo evaporation as applied commonly encountered in extraction procedures [37, 45]. 

Capillary electrophoresis (CE) coupled to MS has the advantage of high resolution and soft ionization for biomolecules, which may be used to differentiate post-translational modifications and variants of intact proteins and oligonucleotides. Different modes of CE (capillary zone electrophoresis, capillary isoelectric focusing, capillary electrochromatography, micellar electrokinetic chromatography, nonaqueous capillary electrophoresis) to MS as well as online preconcentration techniques (transient capillary isotachophoresis, solid-phase extraction, membrane preconcentration) are used to compensate for the restricted detection sensitivity of the CE methodology [77, 78]. 

A methodological approach for an effective and reliable quality control of Chinese star anise [I. verum Hook. F.) was developed and validated by Lederer et al. (2006). A combined method of TLC and HPLC-MS/MS was used for differentiation ofvarious Ulicium species, especially Chinese and Japanese star anise. Species can be distinguished by their TLC flavonoid pattern. A sensitive and selective HPLC/ESI-MS/MS method was developed for the detection and quantification of lower admixtures of I. anisatum and of further toxic Ulicium species at a low concentration range using the sesquiterpene, lactone anisatin, as a marker. This assay includes a solid-phase extraction clean-up procedure with a high recovery (> 90%). 

Recently, Hawthorne et al. coupled the ASE technique to solid-phase extraction using sorption discs that were placed in the extraction chamber together with the sample in order to simultaneously concentrate and extract polar compounds such as acid herbicides and their esters from soils, using strong anion-exchange (SAX) discs [99]. They also used this combined methodology to develop a convenient method of shipping extracts from field sites to the analytical laboratory [100]. In the former application, the esters of the... 

The procedure to be used to extract carbamate pesticides from environmental samples depends on their polarity and on the type of sample matrix involved. Various choices exist for the extraction of pesticides ranging from conventional procedures (e.g., Soxhlet extraction, liquid-liquid extraction (LLE), evaporation, steam distillation) to new methodologies including solid-phase extraction (SPE), solid-phase microextraction (SPME), supercritical fluid extraction (SEE), matrix solid-phase dispersion (MSPD), accelerated solvent extraction (ASE) and microwave-assisted extraction. " ... 

Recently, Blount et al. (2000) summarized a methodology to detect di- -butyl phthalate metabolites in urine. In humans or animals, di- -butyl phthalate is metabolized to mono- -butyl phthalate and oxidative products, which are excreted through the urine and feces. Human urine samples are processed by P-glucuronidase hydrolysis (to release the mono phthalate ester) followed by solid-phase extraction. The eluate is concentrated mono- -butyl phthalate is chromatographically resolved by reverse-phase HPLC, detected by negative ion atmospheric pressure chemical ionization (APCI) tandem mass spectrometry, and quantified by isotope dilution. 

The extension of the methodology for determination of cephalexin by using the H-point standard additions method (HPSAM) and the generalized H-point standard additions methods (GHPSAM) (after solid phase extraction cartridges) permitted also its analysis in urine [53]. 

Olsen, J. Martin, P. Wilson, I.D. Jones, G.R. Methodology for assessing the properties of molecular imprinted polymers for solid phase extraction. Analyst 1999,124, 467 71. 

The monomers used to prepare the imprinted polymers for the triazine herbicides were acrylamidopropyl sulfonic acid (AMPS) and methylenebisacrylamide (BIS). This methodology has also been used in the synthesis of imprinted membranes used in the solid phase extraction of terbumeton, another member of the group of triazine herbicides form water [59]. 

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