Solid phase extraction preparation techniques

Sample preparation includes any manipulation of the sample prior to analysis, including such techniques as weighing, dilution, concentration, filtration, centrifugation, and liquid- or solid-phase extraction. These techniques may be performed with the aid of devices such as... 

Metabolite/residue analysis. Milk, urine and plasma samples were first analyzed by a microbiological cylinder/plate procedure against M.luteus which has a limit of detection of 0.02 ppm. A sub-sample of the milk was prepared for this assay by a centrifugation step followed by a pH adjustment to 8.5. In addition, an HPLC/RAM analysis was conducted after treating another sub-sample with FTSH (10% formic acid, 30% trifluoroacetic acid, 2% sodium chloride, 2N hydrochloric acid) followed by centrifugation to precipitate the proteins. The supernatant was basified and concentrated by C-18 solid phase extraction (SPE) techniques. The HPLC conditions were Column - 20 cm x 4.8 mm C-8 Mobile-phase -linear gradient at 5%/minute from 90 10 O.IM pH 7 phosphate buffer methanol to 20 80 Detectors - UV operated at 214 nm and a radioactivity flow detector operated in the DPM mode. 

Solid phase extraction (SPE) techniques are emerging as the perhaps most popular alternatives to liquid-liquid extraction for sample preparation of food and agricultural samples. The principle of SPE is now fully described (9,10). Most sorbents are now available as disks, cartridges or precoiumns (11,12). Among the advantages of SPE, is die easiness for the method to be automated and the possibility for simultaneous combination of extraction and enrichment of the analytes (12). This reduces the whole analytical scheme compared to liquid-... 

The use of solid phase extraction (SPE) techniques in sample preparation is widely spread, since a wide variety of substrates interacting variously with different metal species or organic compounds is available (Fritz 1999). Furthermore, SPE procedures are well suited for automatization and usually require less organie solvents than liquid-liquid extraction techniques. 

For a description of this method see Zief, M. Kiser, R. Am. Lab. 1990, 22 70 Zief, M. NEACT. 1990, 8, 38 Hagen, D. F. Markell, C. G. Schmitt, G. A. Blevins, D. D. Anal. Chim. Acta 1990, 236, 157 Arthur, C. L. Pawliszyn, J. Anal. Chem. 1990, 62, 2145 Dorsey, J. Dill, K. A. Chem. Rev. 1989, 89, 331 Zubrick, J. W. The Organic Chem Lab Survival Manual, 7th ed., Wiley New York, 2008 Simpson, N. J. K, Ed. Solid-Phase Extraction Principles, Techniques and Applications, Marcel Dekker New York, 2000 "Solid Phase Extraction." Retrieved March 19, 2009 from www.sigmaaldrich.com/analytical-chromatography/sample-preparation/spe.html. 

It is also possible to perform preparative TLC, developing the sample with AMD technique [36a]. After a solid-phase extraction of the waste water with C18-Empore discs, alkanesulfonate is isolated by using a specially dimensioned TLC plate and by scraping out the surfactant-containing zone. 

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

The need to understand the fate of pesticides in the environment has necessitated the development of analytical methods for the determination of residues in environmental media. Adoption of methods utilizing instrumentation such as gas chro-matography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid chromatography/tandem mass spectrometry (LC/MS/MS), or enzyme-linked immunosorbent assay (ELISA) has allowed the detection of minute amounts of pesticides and their degradation products in environmental samples. Sample preparation techniques such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), or solid-phase microextraction (SPME) have also been important in the development of more reliable and sensitive analytical methods. 

Principles and Characteristics Solid-phase extraction (SPE) is a very popular sample preparation and clean-up technique. In SPE solutes are extracted from a liquid (or gaseous) phase into a solid phase. Substances that have been extracted by the solid particles can be removed by washing with an appropriate liquid eluent. Usually, the volume of solvent needed for complete elution of the analytes is much smaller (typically < 1 mL) than the original sample volume. A concentration of the analytes is thus achieved. 

This chapter will review recent advances in mass spectrometry, liquid chromatography, and sample preparation techniques that aim at achieving high throughput. In particular, online solid phase extraction and multiplexed HPLC front ends for quantitative bioanalysis will be discussed in detail. 

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

Zimmer D. et al., 1999. Comparison of turbulent-flow chromatography with automated solid-phase extraction in 96-well plates and liquid-liquid extraction used as plasma sample preparation techniques for liquid chromatography-tandem mass spectrometry. J Chromatogr A 854 1999. 

Liquid chromatographic clean up [441,443,450] has been used either in normal phase flow using alumina, silica, or florisil [22,189,403,481,484] or with reverse-phase (RP) columns [409,452,480]. In most cases these techniques are well established and are used in an off-line mode, primarily to remove the bulk of co-extracted materials prior to a more refined clean-up prior to the final determination. These columns may be prepared in the laboratory [22,403 -405] or commercial solid phase extraction (SPE) cartridges can be used [409,452, 463,470,485,486]. In both cases, the normal phase cartridges and column materials are disposable since many of the polar co-extractants bind firmly to the substrate surface and are difficult to remove. This has been overcome to some... 

Sample preparation refers to a family of solid/liquid handling techniques to extract or to enrich analytes from sample matrices into the final analyte solution. While SP techniques are well documented, few references address the specific requirements for drug product preparations, which tend to use the simple dilute and shoot approach. More elaborate SP is often needed for complex sample matrices (e.g., lotions and creams). Many newer SP technologies such as solid-phase extraction... 

Before compounds in biological matrices can be analyzed by LC/MS/MS, the samples must undergo a preparation procedure. There are a variety of techniques available for sample preparation including offline sample preparation techniques (liquid-liquid extraction, protein precipitation, and solid phase extraction) and on-line sample preparation... 

Section II covers the latest trends in reducing sample preparation time, including direct sample infusion/injection and on-line solid phase extraction (SPE). In Section III, we focus on newer trends in stationary phases and how these phases hope to offer different selectivities compared to current CIS-based phases. Section IV briefly provides a few observations on how new detectors are increasing the versatility of HPLC. Finally, in Section V we examine monolithic columns, small particles packed in short columns, high-temperature LC, ultra high-pressure LC, and parallel injection techniques. 

As well as typical sample preparation methods such as filtration and liquid-liquid extraction, newer developments are now extensively used. The first of these is solid-phase extraction (SPE). This is a rapid, economical, and sensitive technique that uses several different types of cartridges and disks, with a variety of sorbents. Sample preparation and concentration can be achieved in a single step. Interfering sugars can be eluted with aqueous methanol on reversed-phase columns prior to elution of flavonoids with methanol. 

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