Solid-phase extraction experiment

EXECUTING THE SOLID-PHASE EXTRACTION EXPERIMENT IN FIVE STEPS... 

A simple predecessor of the CEM setup for microwave-mediated SPOS was employed by Murray and Gellman in their synthesis of 14-hehcal 6-peptides [42], A 4 mL polypropylene solid-phase extraction tube was inserted into a 10 mL CEM vessel, allowing for both microwave heating and simple resin manipulation (Eig. 11). While using this setup gave reproducible results for their experiments, a discrepancy between the reactions target (set) temperatures and the actual temperatures was observed. Therefore, use... 

GC, utilizing flame ionization detection (FID), has been used to measure diisopropyl methylphosphonate in meat, grain, or milk (Caton et al. 1994). Sample preparation steps include homogenization, filtration, dialysis, and extraction on a solid sorbent. Two common solid phase extractants, Tenax GC and octadecylsilane bonded silica gel (C18 Silica), were compared by Caton et al. (1994). They reported 70% recovery when using Tenax GC and 85% recovery when using C18 Silica. Sensitivity was not reported. Equilibrium experiments indicate that 8-10 mg of Tenax GC are required to achieve maximum recovery of each g of diisopropyl methylphosphonate (Caton et al. 1994). By extrapolating these... 

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]. 

To illustrate potential problems that may occur with real samples, the effect of flow rate was investigated. To demonstrate this effect, riboflavin was trace-enriched from 10 mL of an aqueous solution. A fresh solid-phase extraction device was properly conditioned and used for each experiment. The surface of the solid phase must be solvated so that the cartridge can be properly conditioned. Directions for solvating the surface can be found in the operating instructions that accompany the cartridge. 

While the experiment has been tested on the SepPak brand, equivalent solid-phase extraction devices should also work in this experiment. As an alternative, homemade columns can be constructed from Pasteur pipets plugged with glass wool at the outlet tip and dry-packed with bulk packing material (refer to Chapter 6 for details). Silica gel (200 mesh) can be purchased from many supply houses. Preparative Ci8 packing of 50 to 100-jCtm particle size is available from many chromatography suppliers. 

Fluorous affinity separation was originally used to remove catalysts from complex reaction mixtures [6], A perfluoroalkyl moiety (generally no shorter than -C6F13) is appended to a compound of interest. Tagged molecules are then rapidly separated from other components in the mixture by either liquid-liquid extraction or liquid-solid-phase extraction. Fluorous affinity-based separation has recently been used in biomolecule purification, proteomics, and microarray experiments [15-20],... 

We have applied this protocol to the evaluation of the measurement uncertainty for a method for the determination of three markers (Cl solvent red 24, Cl solvent yellow 124 and quinizarin (1,4-dihydroxyanthra-quinone)) in road fuel. The method requires the extraction of the markers from the sample matrix by solid phase extraction, followed by quantification by HPLC with diode array detection. The uncertainty evaluation involved four experimental studies which were also required as part of the method validation. The studies were precision, trueness (evaluated via the analysis of spiked samples) and ruggedness tests of the extraction and HPLC stages. The experiments and uncertainty calculations are described in detail in Part 2. A summary of the uncertainty budget for the method is presented in Fig. 3. 

Solid-phase extraction (SPE) (Fig. 6) is a miniature version of the liquid chromatography experiment. It was commercialized and introduced in the late 1970s. With the availability of prepacked cartridges, SPE first became popular in the mid-1980s [19]. It has been widely applied to sample cleanup in the drug discovery... 

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