Solid-phase Extraction Of Compounds Research Articles

Molecularly imprinted beads based on modified cellulose hydrogel:A novel solid phase extraction filler for specific adsorption of camptothecin

Traditional solid phase extraction (SPE) suffers from a lack of specific adsorption. To overcome this problem, a combination of adsorption method and molecular imprinting technology by polydopamine modification was proposed to realize specific recognition of target compounds in SPE, which is of great significance to improve the separation efficiency of SPE. Cellulose hydrogel beads were prepared by dual cross-linking curing method and modified with polydopamine to make them hydrophilic and biocompatible. Subsequently, cellulose hydrogel-based molecularly imprinted beads (MIBs) were synthesized by surface molecular imprinting technology and used as novel column fillers in SPE to achieve efficient adsorption (34.16 mg·g−1) with specific selectivity towards camptothecin (CPT) in 120 min. The simulation and NMR analysis revealed that recognition mechanism of MIBs involved hydrogen bond interactions and Van der Waals effect. The MIBs were successful used in separating CPT from Camptotheca acuminata fruits, exhibiting impressive adsorption capacity (1.19 mg·g−1) and efficient recovery of CPT (81.54 %). Thus, an environmentally friendly column filler for SPE was developed, offering a promising avenue for utilizing cellulose-based materials in the selective separation of natural products.

Trace analysis of parabens preservatives in drinking water treatment sludge, treated, and mineral water samples.

Parabens have been widely used as antimicrobial agents, mainly in food products, pharmaceuticals, and cosmetics. Although they are known as safe preservatives, they also cause some harm to human health, which has been discussed lately. Therefore, the aim of this study was to evaluate the occurrence of nine parabens (including isomers) in mineral and drinking waters, besides in drinking water treatment sludge (DWTS) samples with determination by liquid chromatography tandem mass spectrometry (LC-MS/MS). Both methods solid phase extraction (SPE) and QuEChERS were validated. Calibration curves showed a correlation coefficient of 0.99 for all compounds. LOQ values ranged from 0.04 to 4μgL-1 in aqueous matrices and from 5 to 500ngg-1 in DWTS. Recoveries between 70 and 115% were reached with RSD below 20% for all compounds in SPE whereas recoveries between 62 and 119% were found with RSD below 20% for almost all compounds in QuEChERS. Matrix effect had low values (< 20%); it was only above 20% for methylparaben in the SPE and for pentylparaben in the QuEChERS. Using a quick and simple extraction procedures with SPE, QuEChERS, and LC-MS/MS analyses, these methods proved to be selective and sensitive. They were successfully applied to real samples (treated water, mineral water, and sludge), and methylparaben was detected at concentration levels below 0.242μgL-1 in mineral and treated water samples and 10ngg-1 in DWTS samples.

New hydrophilic materials for solid-phase extraction

Solid-phase extraction (SPE) is increasingly being used as a sample-pre-treatment technique to cover a wide range of analytes, including the most polar. This involves the development of new sorbents that are able to trap the most polar analytes. We provide an overview of the new sorbents, both commercially available and synthesized in-house, which improve the extraction of the most polar compounds in SPE. We mainly cover polymeric sorbents with a large specific surface area and a hydrophilic character that is obtained by either copolymerizing polar monomers or introducing polar functional groups. Other novel material technology, such as monoliths, is also described. For these new sorbents, we describe morphological and chemical properties that we relate to their retention capabilities towards polar compounds. We discuss the recoveries of polar compounds when these sorbents are used in SPE and compare them with recoveries when other sorbents are used.

Frontal analysis of aqueous phenol solutions in amberlite XAD-4 columns: Implications on the operation and design of solid phase extraction systems

Frontal analysis of aqueous phenol solutions in Amberlite XAD-4 columns was carried out at different experimental conditions. Operating variables such as the concentration, pH and ionic strength of the influent, the presence of competitor solutes, the fluid flow-rate and the column length were considered and their effects on the front profile, the phenol breakthrough volume and the equilibrium parameters were determined. The obtained results may explain some contradictory reported data concerning the recovery of hydrophilic compounds in solid phase extraction (SPE) systems using Amberlite XAD-2 or XAD-4 columns. Furthermore, it is demonstrated that the adsorption parameters derived from a frontal analysis in an XAD-4 column are directly transposable to columns of different sizes (at the analytical level). Therefore, the results of this study may also be used for prediction and/or design of a phenol SPE system adapted to a particular problem.

Influence of chemical modification of polymeric resin on retention of polar compounds in solid-phase extraction

Three polymeric adsorbents, two of which had been chemically modified with different hydrophilic functional moieties and the third, which was the corresponding unmodified polystyrene-divinylbenzene (PSDVB) resin, were compared for solid-phase extraction (SPE) of several polar pesticides and phenolic compounds from water samples. The SPE system was online coupled to a liquid chromatograph with UV detector.

Effect of resin sulfonation on the retention of polar organic compounds in solid-phase extraction

The hydrophobic nature of polymeric resins used in solid-phase extraction (SPE) often limits their efficiency by preventing intimate surface contact with aqueous samples. A polymeric resin modified by a series of chemical derivatizations with sulfuric acid was found to display excellent surface hydrophilicity and improved extraction efficiencies. The degree of sulfonation was found to play a vital role in determining the SPE efficiency of such resins. By measuring the capacity factor of several polar organic solutes in pure water, an optimum sulfonation capacity of 0.6 mequiv./g was determined. Loose sulfonated resin and Empore membranes embedded with sulfonated resin were used for SPE. Average recoveries were greater than 95% for both types of sulfonated resin for a wide variety of organic compounds including phenols, alcohols, nitro compounds, aldehydes, esters and halogenated alkanes. Breakthrough curves for p-cresol, ethyl acetoacetate, isophorone and nitrobenzene were used to compare Empore membranes embedded with sulfonated and unsulfonated resin. The sulfonated membrane yielded sharper and more efficient breakthrough for all compounds tested.

The role of capacity factor in method development for solid-phase extraction of phenolic compounds. II

Recently, a simple method was developed for the determination of capacity factors of phenolic compounds on solid-phase extraction cartridges [ J. Chromatogr. A, 693 (1995) 217]. In the present paper the capacity factors determined by this method are used to predict recoveries of phenolic compounds in solid-phase extraction at three different sample volumes. The values are compared with those of recovery tests from both model solutions and spiked surface water samples. Based on calibration data the minimum sample concentrations which can be determined by the SPE procedure are also calculated from the capacity factors.