Solid phase extraction purpose

What is the purpose of including an initial solid-phase extraction ... 

Concentration of an analyte prior to measurement may be necessary where the level is likely to be close to or below the practical detection limit of the technique to be used. Solvent extraction, solid phase extraction and ion-exchange may be used for this purpose. Where a complex... 

A recent review by Pichon and Haupt169 summarizes the progress in the area of utilization of MIPs for sample preparation purposes and cites several examples of solid phase extraction (MISPE) from biological matrices. The requirements and applications of MIPs are reviewed in a recent book170 and other literature.171-176... 

Due to the predicted and previously detected low concentrations of pesticides in environmental samples (usually around the nanogram per liter level), a preconcentration step of the water samples is necessary prior to measurement. In this way, a preconcentration factor of several orders of magnitude (200-1,000-fold) is mandatory to reach the low detection limits necessary for the identification of pesticides, especially in complex wastewater samples. Also, the use of surrogate standards (e.g., triphenyl phosphate) added before the extraction step is a common practice in order to account for possible errors during the extraction process and for quantitative purposes. The commonly used extraction methods for polar compounds from water matrices involve isolation using liquid-liquid extraction (LLE) and solid-phase extraction (SPE), which are commented on below. Other methods such as semipermeable membrane devices (SPMD) are also mentioned. 

In order to study simultaneously the behaviour of parent priority surfactants and their degradation products, it is essential to have accurate and sensitive analytical methods that enable the determination of the low concentrations generally occurring in the aquatic environment. As a result of an exhaustive review of the analytical methods used for the quantification within the framework of the three-year research project Priority surfactants and their toxic metabolites in wastewater effluents An integrated study (PRISTINE), it is concluded that the most appropriate procedure for this purpose is high-performance (HP) LC in reversed phase (RP), associated with preliminary techniques of concentration and purification by solid phase extraction (SPE). However, the complex mixtures of metabolites and a lack of reference standards currently limit the applicability of HPLC with UV- or fluorescence (FL-) detection methods. 

Chen XH, Franke JP, Ensing K, Wijsbeek J, De Zeeuw RA. 1993. Pitfalls and solutions in the development of a fully automated solid-phase extraction method for drug screening purposes in plasma and whole blood. J Anal Toxicol 17 (7) 421-426. 

Fig. 18.1 Systems used to absorb aroma compounds from samples for analytical purposes, a Traps loaded with various adsorbents [4]. b Solid-phase extraction (disk in a holder assembly) [5]. c Solid-phase microextraction (coated needle inserted in sample) [5]. d Twister (1 -cm length) [4]. (Courtesy of GERSTEL GmbH and Co. KG)...

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. 

Elimination of coextracted materials and concentration of tetracyclines have also been accomplished using mixed-phase extraction membranes with both re-versed-phase and cation-exchange properties (294,295), or solid-phase extraction columns packed with cation-exchange materials such as CM-Sephadex C-25 (301), aromatic sulfonic acid (310), and carboxylic acid (283, 300). For the same purpose, metal chelate affinity chromatography has also been employed. In this technique, the tetracyclines are specifically absorbed on the column sorbent by chelation with copper ions bound to small chelating Sepharose fast flow column (278-281, 294-296). 

Sample Preparation/Extraction The process of separating potentially interfering components from a sample prior to LC-MS analysis for the purposes of improving sensitivity, specificity, and/or method ruggedness. Variations include solid phase extraction (SPE), liquid-liquid extraction (LLE), and protein precipitation (PPT). Extraction may be performed off-line, in which the cleanup is completely independent from the LC-MS analysis, or on-line, in which the cleanup is integrated directly into the LC-MS analysis. 

Traditional analytical approaches such as GC-MS, HPLC fluorescence, and conventional LC-MS, are not sufficiently sensitive to quantify the low-pg/mL levels of corticosteroids in bodily fluids [4], The purpose of this work was to develop an ultrasensitive and selective approach to quantify corticosteroids present at extremely low, but biologically meaningful concentration in body fluids. A selective solid-phase extraction (SPE) and reversed-phase capillary LC coupled to tandem mass spectrometry (uLC-MS/MS) strategy was employed to achieve a high concentration sensitivity. 

Sample enrichment by solid-phase extraction has several purposes. It not only makes the proteome sample amendable for analysis to a greater extent, it also makes structural information greater. 

The term solid-phase extraction was introduced by personnel of the J. T. Baker Company in 1982. The method consists of retention of the analytes from a liquid or gaseous sample to a solid stationary phase and subsequent removal of analytes using an appropriate eluent. The main purpose of SPE is isolation and preconcentration of compounds of interest or sample clean-up and simplification of the matrix. Application of this sample preparation technique also allows extract fractionation. As a result of significant reduction in the volume of organic solvents used, high recovery, and the possibility of process automation, SPE is a good alternative for conventional liquid-liquid extraction. According to their affinity for the compound of interest, stationary phases are classified as follows ... 

Sample Concentration and/or Purification. Concentrating or purifying an analyte in a sample is often necessary before separation and quantification by HPLC. Several liquid extraction and solid phase extraction (SPE) techniques are used for this purpose. The latter has become very popular... 

Each route of synthesis will result in an impurity profile which can be analysed. Unlike cannabis, heroin and cocaine, the impurities are present in very low concentrations and need to be extracted from the amphetamine matrix. Liquid-liquid extraction (LLE) and solid-phase extraction (SPE) have been most frequently applied for this purpose [13-16], Of these, LLE is currently the most widely used technique. In addition, there are attempts being made to develop the method so that it can be optimized to allow data exchange between different laboratories (in different countries) [17]. 

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