Solid phase extraction technique

Due to the risk of contamination during field extraction of water samples using SPE, it is highly desirable to avoid contact of water being sampled with the mechanical 

Recovery of Spiked Organochlorine Contaminants from Organic-Free and Lake Ontario Water and Suspended Solids 

Source- From Fox, M.E., in Methods for Analysis of Organic Compounds in the Great Lakes, University of Wisconsin Sea Grant Institute, Madison, 1986, 27-34. With permission nd. Not detected. 

An example of a system for high-volume extraction in the field based on solid-phase extraction techniques. 

Published High Volume Solid-Phase Extraction Configurations for Water Sampling in the Field 

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It is noteworthy that trifluoroacetic acid was introduced as the most appropriate acidifler for column chromatography and solid phase extraction techniques, i.e., low boiling point due to its high acidity, requiring low amounts to reach the respective pH. Also, its high volatility allows easy evaporation thus minimizing the thermal load and acidification during concentration. 

Exudate collection in trap solutions usually requires subsequent concentration steps (vacuum evaporation, lyophilization) due to the low concentration of exudate compounds. Depending on the composition of the trap solution, the reduction of sample volume can lead to high salt concentrations, which may interfere with subsequent analysis or may even cause irreversible precipitation of certain exudate compounds (e.g., Ca-citrate, Ca-oxalate, proteins). Therefore, if possible, removal of interfering salts by use of ion exchange resins prior to sample concentration is recommended. Alternatively, solid-phase extraction techniques may be employed for enrichment of exudate compounds from the diluted trap solution (11,22). High-molecular-weight compounds may be concentrated by precipitation with organic solvents [methanol, ethanol, acetone 80% (v/v) for polysaccharides and proteins] or acidification [trichloroacetic acid 10% (w/v), per-... 

Table 3 Summary of solid-phase extraction techniques applied to the preparation of water samples for the determination of triazine pesticides...

Sample preparation—Analytes of interest were extracted from human plasma using the online solid phase extraction technique. The steps required are noted below ... 

Tap water Extract compound with solid-phase extraction technique that uses a membrane impregnated with reverse-phase particles elute with acetonitrile LC Low ppb (pg/L) 82-93 Hagen et al. 1990... 

Product extraction from large volumes of fermentation broth can be complex, requiring large volumes of organic solvent or solid-phase extraction techniques, which can sometimes greatly reduce or even cancel out the benefits of the biotransformation itself, such as shorter route and environmentally benign conditions. 

Krause, A.A. and Niemczyk, H.D. Gas-liquid chromatographic analysis of chlorthal-dimethyl herbicide and its degradates in turfgrass thatch and soil using a solid-phase extraction technique, J. Environ. Sci Health, B25(5) 587-606, 1990. Kresheck, G.C., Schneider, H., and Scheraga, H.A. The effect of DzO on the thermal stability of proteins. Thermod3mamic parameters for the transfer of model compounds from HzO to DzO, J. Phys. Chem., 69(9) 3132-3144, 1965. 

Solid-phase extraction techniques that are based mostly on reversed-phase (Cis) sorbents, have been also widely used for cleanup and concentration purposes (23, 25, 27, 31, 34, 37, 46, 51, 52, 55, 65). However, many applications have indicated that cleanup using these nonpolar materials may not be very effective in removing interfering substances from sample extracts. Hence, polar sorbents such as silica (23, 26, 29, 30, 32, 40, 42, 44, 52, 53) or Florisil (45) have been also suggested as more powerful alternatives for the isolation and/or cleanup of amphenicols. 

Simjouw, J.-E, Minor, E. C., and Mopper, K. (2005). Isolation and characterization of estuarine dissolved organic matter Comparison of ultrafiltration and C18 solid-phase extraction techniques. Mar. Chem. 96, 219-235. 

Kaye, B. Herron, W. J. Macrae, P. V. Robinson, S. Stopher, D. A. Venn, R. F. Wild, W. 1996. Rapid, solid phase extraction technique for the high-throughput assay of darifenacin in human plasma. Anal. Chem., 68,1658-1660. 

Analytes may accumulate in the sorption phase either by adsorption onto the surface of solid sorbent materials or by absorption in absorbent liquids or polymers that behave like subcooled liquids.The advantage of solid adsorbents is the potential to select materials with a high affinity and selectivity for target analytes. However, the sorption capacity of adsorbents is usually limited, and the description of adsorption/desorption kinetics of analytes to adsorbents is complex. Typically, the adsorbent materials used in passive samplers are similar to those used in solid-phase extraction techniques. 

Both column chromatography and HPLC are used routinely for sample preparation, particularly for protein samples after particulate contamination has been removed by filtration or centrifugation. In addition, the use of ultrafiltration or solid-phase extraction techniques prior to chromatography often will result in a simplified, more concentrated sample. 

Aminoquinolines 62 have been prepared in a two-step, one-pot, three-component reaction of 2-azidobenzophenones, secondary amines and arylac-etaldehydes [110]. The microwave-assisted reaction proceeded via the initial formation of enamines 59. Subsequent addition of 2-azidobenzophenones 60 afforded the triazoline intermediates 61, which underwent thermal rearrangement and cyclocondensation to furnish 2-aminoquinolines 62 (Scheme 41). Direct comparison with conventional thermal conditions demonstrated the superiority of microwave dielectric heating in terms of yields (73% vs. 31% of heterocycle 63 after 10 min at 180 °C). Furthermore, the formation of by-products due to decomposition of azide 60 was diminished in the microwave-assisted synthesis. Purification of the products was achieved using solid-phase extraction techniques. 

Combined with expedient purification techniques (e.g., scavengers, reagents on solid support, and solid phase extraction techniques) [ 14], microwave-assisted synthesis is leading the way towards genuine high-throughput chemistry that will hopefully ease the chemistry-related bottleneck in the drug development process. 

Solid phase extraction techniques have been applied both in the isolation and clean-up of flavor extracts. As an example, Uhlig et al. (22) extracted celery with dichloromethane and then passed the dichloromethane extract over a LC-Si Supelclean cartridge. 

Heymann, et al (24) have used solid phase extraction techniques for the isolation of pyrazines from wines. In this analysis, it was necessary to first distill the pyrazines from the wine and then pass the distillate through a Sep-Pak C-18 cartridge (Waters Assoc.). To speed the analysis, the distillate was forced through the cartridge at a rate of 30 ml/min. 

J.A. T0rnes, A.M. Opstad and B.A. Johnsen, Use of solid-phase extraction in determination of chemical warfare agents. Part I Evaluation of the solid-phase extraction technique, Int. J. Environ. Anal. Chem., 44, 209-225 (1991). 

A number of techniques can be used to isolate analytes from water. The technique used will depend on the volatility of the analyte. Volatile compounds (i.e., more volatile than n-C12) can be analyzed using Purge and Trap techniques or by Headspace analysis. Semivolatile compounds are extracted using liquid—liquid or solid phase extraction techniques. 

Krishnan, T. R. and Ibraham, 1., Solid-phase extraction technique for the analysis of biological samples, /. Pharm. Biomed. Anal, 12, 287, 1994. 

In a subsequent study, solvent partitioning and solid-phase extraction techniques were used to produce a partial ly -pur If led extract (15). The first step In the purification scheme Involved partitioning of a highly oonoentrated ethanol 1c extract of house fly ovaries between chloroform and water. Further processing of the chloroform layer (I.e., evaporation, solvent exchange, and filtration through a bed of Porapac Q) eventually produced a methanol 1c extract with a 23-fold Increeee In OH activity over the crude extract. 

Donat, J. R., Statham, P. J., and Bruland, K. W. (1986) An Evaluation of a C-18 Solid Phase Extraction Technique for Isolating Metal-Organic Complexes from Central North Pacific Ocean Waters, Mar. Chem. 18, 85-99. 

Stationary phases (silica, reversed phases, Amberlite, and Sephadex) or by solid-phase extraction techniques using different adsorbents, which in the last decade has been found very convenient for the isolation of flavonoids from complex matrices. 

Solid-phase extraction, or liquid-solid extraction, can overcome several of these problems. Solid-phase extraction techniques use membranes or small disposable syringe-bairel columns or cartridges. A hydrophobic organic compound is coated or chemically bonded to powdered silica to form the solid extracting phase. The compounds can be nonpolar, moderately polar, or polar. For example, an octadecyl (C jj) bonded silica (ODS) is a common packing. The functional groups bonded to the packing attract hydrophobic compounds in the sample by van der Waals interactions and extract them from the aqueous solution. 

Liska, I., Krupcik, J., and Leclercq, P. A. 1989. The use of solid sorbents for direct accumulation of organic compounds from water matrices—A review of solid-phase extraction techniques, J. High Resol. Chromatog., 12 577-590. 

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