Solid-phase extraction isolation

Solid-Phase Extractions In a solid-phase extraction the sample is passed through a cartridge containing solid particulates that serve as the adsorbent material. For liquid samples the solid adsorbent is isolated in either a disk cartridge or a column (Figure 7.17). The choice of adsorbent is determined by the properties of the species being retained and the matrix in which it is found. Representative solid adsorbents... 

Prepai ative isolation of nonvolatile and semivolatile organic compounds fractions (hydrophobic weak acids, hydrophobic weak bases, hydrophobic neutrals, humic and fulvic acids) from natural and drinking waters in optimal conditions was systematically investigated by solid-phase extraction method with porous polymer sorbents followed by isolation from general concentrate of antropogenic and/or toxic semivolatile compounds produced in chlorination and ozonation processes. 

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. 

Carmine extracted from cochineal insects is one of the most used natural colorings for beverages and other foods. Some representative articles refer to isolation and spectrometric analysis or the use of HPLC or capillary electrophoresis (CE) to separate and characterize all cochineal pigments. Its active ingredient, carminic acid, was quantified by rapid HPLC-DAD or fluorescence spectrometry. Carminic acid, used as an additive in milk beverages, was separated within 9 min using a high-efficiency CE separation at pH 10.0 after a previous polyamide column solid phase extraction (SPE), ... 

Another equally important consideration before development of a determinative or confirmatory method is an understanding of the chemical properties of the analyte. Such an understanding becomes the cornerstone of a successful method since the unique chemical properties of each analyte provide the basis for isolation and detection schemes. Table 1 lists some of the important chemical properties that could be considered. For example, knowing the or p/fb of an analyte could influence the choice of a liquid-liquid extraction scheme, solid-phase extraction (SPE) cartridge, mobile phase pH, or mass spectrometric ionization. Knowing the overall polarity of the analyte can be very helpful in the evaluation of an extraction or separation. Currently, computational methods are available to obtain an estimate of the logP... 

Solid phase extraction (SPE) is a very simple, rapid and reproducible cleanup technique that is now widely accepted as an alternative to the time-consuming liquid-liquid extractions. Additionally, SPE uses relatively small volumes of solvents, and is easy to automate. It is available in a number of different formats, including cartridges, disks, loose material, well plates or SPME using film-coated capillaries. SPE can be considered as an extraction technique when used for isolation and concentration or a cleanup technique when used to remove co-extractives from solvent extracts. The use of SPE for cleanup is discussed later. 

Recently, solid phase extraction (SPE) has been used to isolate members of this class of compounds. No solid phase support has been used exclusively and both hydrophobic- and hydrophilic-based solid phase extraction columns have been used for this assay. 

Fluorous ligands introduce an ease of purification in that the tagged phosphine ligand, the palladium catalyst complexed ligand, and the oxidized ligand can be completely removed by direct fluorous solid-phase separation (F-SPE) prior to product isolation. Similarly, an example of a fluorous palladium-catalyzed microwave-induced synthesis of aryl sulfides has been reported, whereby the product purification was aided by fluorous solid-phase extraction [91]. 

The assembly of tetrapeptide 19 that contains all possible 0-dipeptide bonds, (03-03)-, (03-02)-, and (02-03), and also a turn inducing 03-(R)-Ala-02-(R)-Val element was achieved employing a Boc-strategy (Scheme 5). A fluorous benzyl group was incorporated in the first amino acid to streamline the purification procedure by fluorous solid phase extraction (LSPE) (Lilippov et al. 2002 de Visser et al. 2003). Thus, the assembly of the fully protected tetrapeptide commenced with the construction of the first 03-03-peptide bond by applying the previously established conditions. A residence time of 3 min at 90°C provided the Boc-protected dipeptide 15 in 91% isolated yield after LSPE. Notably, the product precipitated in the collection flask, which was kept at ambient temperature, indicating the poor solubility of this class of compounds (Hessel et al. 2005). 

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. 

Mills and Thurman [105] studied the mixed mode isolation of Triazine metabolites from soils using automated solid phase extraction with methanohwater (4 lu/u) extracts of the sample. Methanol is evaporated from the extract and the metabolites are collected on an octadecyl resin (Cl8) column. The analytes are eluted with ethyl acetate leaving the impurities on the C18 resin column. The detection limit of this method is 0-lgg kg 1-... 

Mills and Thurmen [105] used a mixed method for the isolation of triazine herbicide metabolites from aquifer sediments using automated solid phases extraction with a mixture of methanol and water (4 1 V/V). Following evaporation of the methanol phases, the metabolites were collected in a column of Cl8 octadecyl resin. The analytes were then stripped from the column with ethyl acetate leaving impurities on the column. Down to O.lpg kg-1 triazine could be determined. 

Fish. Solid biota samples, mainly fish, should be quickly killed by liquid N2 [28] or cervical dislocation [32] and kept at low temperatures (— 20°C). Some authors preferred desiccation of the sample at high temperature (70°C) [33,34] or lyophylisation [28]. The extraction and isolation steps would be combined when using lyophylisation and homogenisation, followed by a Soxhlet extraction, usually with MeOH, and a subsequent solid-phase extraction (SPE) clean-up, prior to the quantification. 

Solid phase extraction followed by capillary zone electrophoresis with UV absorbence detection has been shown to be applicable to the isolation and determination of 3,3 -dichlorobenzidine in water at ppm levels (Cavallaro et al. 1995). 

Experiments to identify disinfection by-products (DBFs) have been carried out using two different procedures. In the first, natural waters (e.g., river, lake) are reacted with the disinfectant, either in a pilot plant, an actual treatment plant, or in a controlled laboratory smdy. fii the second type of procedure, aquatic humic material is isolated and reacted with the disinfectant in purified water in a controlled laboratory study. This latter type of study is relevant because humic material is an important precursor of THMs and other DBFs. Aquatic humic material is present in nearly all natural waters, and isolated humic material reacts with disinfectants to produce most of the same DBFs found from natural waters. Because DBFs are typically formed at low levels (ng/L-pg/L), samples are usually concentrated to allow for DBF detection. Concentration methods that are commonly used include solid phase extraction (SFE), solid phase microextraction (SFME), liquid-liquid extraction, and XAD resin extraction (for larger quantities of water) [9]. 

Analytical Methods Development. A solid-phase extraction (SPE) method that will isolate and fractionate metolachlor and its oxanilic acid (OXA) and ethanesulfonic acid (ESA) metabolites from soil and water will be developed. The SPE method will be used... 

Significant improvements in the isolation of pharmaceutical compounds from plasma, serum and urine, have been achieved using ultra low mass sorbent bed and thin disk solid-phase extraction (SPE) material. The use of low sorbent masses or disk SPE material has allowed a significant reduction in solvent usage and extraction times. Several SPE RP-HPLC methods have been developed using these materials, including... 

More recently, several aroma compounds were isolated from cupuacu pulp by vacuum distillation, solid-phase extraction, and simultaneous steam distil-lation-extarction and were analysed by GC, GC-MS, and GG-O [8]. The olfaction of the extracts obtained by solid-phase extraction indicated linalool, a-ter-pineol, 2-phenylethanol, myrcene, and limonene as contributors of the pleasant floral flavour. In this study, the esters ethyl 2-methylbutanoate, ethyl hexanoate, and butyl butanoate were involved in the typical fruity characteristics. 

A contemporary of the method just described is the use of an absorbent (e.g. C-18) bonded onto granular or disk-type supports (solid-phase extraction [5]). The granular material is used in cartridge form (typically less than 5 ml), while disk forms are placed in a funnel/holder such as shown in Fig. 18.1b. A liquid (e.g. water, milk, or juice) would be passed through the cartridge (or filter disk), the analytes absorbed in the stationary matrix, the absorbent washed with water, and then the analytes of interest eluted from the absorbent with an organic solvent. This method has found limited use in the isolation of volatiles from foods but continues to find significant application in the analytical field overall [6]. 

Human serum sample (0.5 ml), diluted with 2.5 ml of 0.1 N NaOH is incubated at 65°C for 15 min. The free, and glycine- and taurine-conjugated fractions are isolated by means of solid-phase extraction, using BE C18 and BE SAX cartridges in succession [23]. The taurine fraction is enzymatically hydrolysed according to a previously described method [24]. The final residue is treated with 1 ml volume of 0.01% (w/v) KOH methanolic solution (methanokwater 1 9, v/v) at 40°C by ultrasonication for 3 min. Then, 0.2 ml of the obtained suspension is derivatised as described below. BA content is determined in each sample by comparison with an appropriate standard solution. 

---