Solid-phase Extraction Of Polar Compounds Research Articles

Hydrophilic interaction chromatography-type sorbent prepared by the modification of methacrylate-base resin with polyethyleneimine for solid-phase extraction of polar compounds.

Hydrophilic interaction chromatography (HILIC)-type sorbents were newly developed for the solid-phase extraction (SPE) of polar compounds. Two methacrylate-base resins with different cross-linking monomers and pore properties were synthesized, and three polyethyleneimines (PEIs) with different molecular weights were modified onto each base resin. In both cases, PEIs with a molecular weight of 10,000 (PEI-10,000) exhibited the highest adsorption properties for polar compounds (uracil, uridine, adenosine, cytidine, and guanosine). To control the water-enriched layer at the surface of the PEI-10,000-modified sorbents, the additive amount of PEI-10,000 in the modified reaction was also optimized. When 10 times the amount of PEI-10,000 to each base resin was added, an improvement in adsorption property was observed. Moreover, the use of a nonaqueous sample solution (100% acetonitrile) during the sample loading process drastically improved adsorption, especially for uracil (about 80%) and adenosine (100%). These results indicate that the formation of a strong water-enriched layer at the surface of sorbents with an effective expression of hydrophilic interaction was an important factor in the adsorption properties of polar compounds in HILIC mode-SPE.

Preparation and Evaluation of Methacrylate-based Reversed-phase Sorbents for Solid-phase Extraction of Polar Compounds

In solid-phase extraction (SPE), hydrophilic-lipophilic balance (HLB) type sorbents prepared by copolymerization with divinylbenzene (DVB) and polar monomers are widely used. The hydrophobicity of the HLB-type sorbents depends on DVB as the main component, and the extraction efficiency for polar compounds is enhanced by interaction with the polar groups introduced by polar monomers. On the other hand, high adsorption ability, due to the hydrophobicity of DVB, adversely affects the rapid elution of trapped compounds. In this study, the non-aromatic sorbents that has high adsorption ability for polar compounds, and can rapidly elute polar compounds including aromatic rings were developed. Porous polymer particles were prepared with trimethylolpropane trimethacrylate (TMPT), and the solid-phase extraction characteristics were evaluated. By optimizing the pore characteristics of TMPT-type sorbent, it was possible to effectively extract the nucleobases and nucleosides whose extraction efficiency was comparable to that of the commercial HLB-type sorbent. Furthermore, in order to improve the hydrophobicity of the TMPT-type sorbents, non-aromatic sorbents copolymerized with stearyl methacrylate (SMA) were prepared. However, the adsorption abilities of the TMPT-type sorbent could not be improved. The adsorption and desorption properties of the non-aromatic sorbents were evaluated using the TMPT-type sorbent. The aromatic polar compounds were able to be strongly sorbed to the TMPT-type sorbent, but they could be rapidly eluted by low concentration organic solvent as eluent. These results suggest that the TMPT-type sorbents are useful for a solid-phase extraction of the polar compounds and will solve the problem of the poor desorption in the HLB-type sorbents containing DVB.

Evaluation of a new hypercrosslinked polymer as a sorbent for solid-phase extraction of polar compounds

A new hypercrosslinked polymer (HXLGp) with hydrophilic character due to the presence of hydroxyl moieties has been tested as a sorbent for the solid-phase extraction (SPE) of several polar compounds from water samples. This new sorbent enables the on-line extraction of 300 ml of sample with recoveries higher than 80% for polar compounds such as oxamyl, methomyl or desisopropylatrazine (DIA). The HXLGp has also been compared to other commercially available sorbents such as Oasis ® HLB (hydrophilic macroporous), to hydrophobic hypercrosslinked resins and to a previously synthesized sorbent based on N-vinylimidazole-divinylbenzene. The results are consistently better with the new synthesized sorbent. The method was successfully applied to the on-line SPE-HPLC of tap and river water samples. The validation with river water samples provided good linearity range and detection limits between 0.03 for methomyl and 4-nitrophenol (4NP) to 0.2 μg l −1 for phenol (Ph).

Comparison of Hydrophilic Polymeric Sorbents for On-Line Solid-Phase Extraction of Polar Compounds from Aqueous Samples

Two 4-vinylimidazole-divinylbenzene (4VIm-DVB) polymers were synthesized and applied as sorbents for on-line solid-phase extraction (SPE) followed by liquid chromatography for analyzing polar compounds in aqueous samples. The new sorbents (4VIm-DVB) were compared to another sorbent that had been previously synthesized by our group (N-vinylimidazole-divinylbenzene (NVIm-DVB)) and to the commercial OASIS® HLB and StrataTM X.

New hydrophilic polymeric resin based on 4-vinylpyridine–divinylbenzene for solid-phase extraction of polar compounds from water

A 4-vinylpyridine–divinylbenzene (VP–DVB) resin was synthesized to be used for on-line solid-phase extraction process and it was tested for a group of polar compounds. The high specific surface area and the nitrogen content of the VP–DVB sorbent increased the interactions with the polar analytes in the preconcentration process. The sorbent enabled 100 ml of water to be concentrated with recoveries higher than 70% for several polar compounds (including phenol) except for oxamyl (55%) and methomyl (43%). The method was used to analyse water samples by liquid chromatography and UV detection. Linearity was good and detection limits were 0.1–0.2 μg l −1 for all compounds. Several tap and river water and waste water treatment plant samples were analyzed; phenol and (4-chloro-2-methyl-phenoxy)acetic acid (MCPA) were tentatively determined in some samples.

Solid-phase extraction of polar compounds with a hydrophilic copolymeric sorbent

A new synthesized copolymer based on N-vinylimidazole–divinylbenzene (VIm–DVB) was tested as a sorbent for the solid-phase extraction (SPE) of polar analytes. In the on-line SPE, this synthesized sorbent enabled 100ml of sample to be preconcentrated with recoveries as high as 80% for oxamyl, phenol (Ph) and derivates, bentazone and (4-chloro-2-methylphenoxy)acetic acid (MCPA). For the off-line SPE, 1000ml of sample was extracted and recoveries were higher than 92% for all compounds with the exception of oxamyl (83%) and methomyl (78%). The VIm–DVB sorbent gives better recoveries than the previously synthesized 4-vinylpyridine–divinylbenzene (VP–DVB) resin and similar to such highly crosslinked commercial sorbents as LiChrolut EN or Oasis HLB. Real water samples were used to validate the on-line SPE method. Linearity was good and detection limits were between 0.1 and 0.2μgl−1.

Comparison of sorbents for solid-phase extraction of polar compounds from water

Octadecyl-bonded silica, styrene—divinylbenzene and hydroxyethyl methacrylate—ethylene dimethacrylate sorbents were tested for their ability to preconcentrate aniline, benzothiazole, cyclohexanone and cyclohexanol. Breakthrough curves for these compounds were measured for aqueous solutions at pH 5.8 and 10.0 by gas chromatographic analysis of fractions of the aqueous effluents. Elution curves of the analytes in methanolic eluates were obtained in order to determine the optimum volume of the eluate. Using breakthrough volumes and widths of the elution curves, theoretical preconcentration factors were calculated for all analyte—aqueous sample—sorbent systems tested. Octadecyl-bonded silica and styrene—divinylbenzene sorbents were found to be suitable for the preconcentration of weakly polar to polar compounds for practical water quality control purposes.