Effects of hydrophilic monomers on sorptive properties of divinylbenzene-based reversed phase sorbents

Microwave-assisted esterification and electro-enhanced solid-phase microextraction of omega-3 polyunsaturated fatty acids in eggs

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs), a type of fatty acid that has many health benefits, are of increasing concern. Herein, we developed a method for the rapid esterification and enrichment of ω-3 PUFAs in eggs, which includes microwave-assisted esterification (MAE) and electrically enhanced solid-phase microextraction (EE-SPME). Combined with gas chromatographic, efficient detection of ω-3 PUFAs was achieved in eggs. Under microwave radiation, the esterification efficiency exhibited a significant increase ranging from 5.06 to 10.65 times. The EE-SPME method reduced extraction time from 50 to 15 min. In addition, improvements in extractive fiber coating materials were explored, which ensured efficient extraction of ω-3 PUFAs. Under the optimal conditions, the method displayed a low detection limit (1.01-1.54 μg L-1), good recoveries (85.82%-106.01%), and wide linear range (7.5-1000 μg L-1), which was successfully applied to determine ω-3 PUFAs in real egg samples.

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.

Poly(divinylbenzene) as a fiber coating for headspace solid-phase microextraction of polycyclic aromatic hydrocarbons from river water

Porous polydivinylbenzene microspheres with high specific surface area were prepared by distillation-precipitation polymerization, and were used as the coating material in headspace solid phase microextraction for extracting polycyclic aromatic hydrocarbons. Compared with the other reported sorbents, PDVB exhibits lower cost and higher extraction efficiency, and the enrichment factors can reach 5963-16 720.

Molding-type Solid-phase Extraction Media Glued with Commercially Available Adhesives

The handling of a particulate sorbent for solid-phase extraction is often troublesome because it causes static clinging and scattering. To overcome this problem, a production method for a simple molding-type solid-phase extraction medium (M-SPEM) was developed in this study by using commercially available adhesives. The content of a particulate sorbent can increase to as much as 85 wt% in the M-SPEM. Because of the high content, the proposed M-SPEMs have a higher specific surface area than previous monolithic media.

Development and Evaluation of HILIC-type Sorbents Modified with Hydrophilic Copolymers for Solid-phase Extraction

Hydrophilic interaction chromatography (HILIC) has attractive attention for the separation of water-soluble compounds via HPLC. There are, however, few studies on the pretreatment of the HILIC-type solid-phase extraction (SPE) due to the difficulty of obtaining the HILIC-type sorbent. Therefore, the development of HILIC-type sorbents for SPE is essential. In this study, four different hydrophilic copolymers, namely diallylamine-maleic acid copolymer (DAM), diallylamine-acrylamide copolymer (DAA), allylamine-maleic acid copolymer (MAM), and partly methylcarbonylated allylamine acetate copolymer (MAC), were immobilized on glycidyl methacrylate (GMA)-base resin, and their adsorptive properties were evaluated. The results of the physical and adsorptive properties indicated that a balance between the water content of the water-enriched layer on sorbent and the amount of hydrophilic copolymer immobilized on the GMA-base resin was vital for the adsorption in HILIC-type sorbent for SPE.

Evaluation of the adsorption properties of nucleobase-modified sorbents for a solid-phase extraction of water-soluble compounds

We developed hydrophilic interaction chromatography (HILIC)-type sorbents modified with nucleobases for solid phase extraction (SPE). The synthesized hydrophilic base resins were modified by each nucleobase (adenine, guanine, and cytosine). The measurement of the amount of water content indicated that each nucleobase-modified sorbent had a water layer. To evaluate the adsorption properties in the HILIC mode, we chose two nucleobases (uracil and adenine) and four nucleosides (uridine, adenosine, cytidine, guanosine) as water-soluble analytes, which were loaded into an SPE cartridge packed with the nucleobase-modified sorbent. Firstly, 95% acetonitrile (ACN) solutions were used in the process of conditioning and sample loading of the above polar analytes. High recoveries of the analytes were observed in each nucleobase-modified sorbent, and the Diol-type sorbent (no modification with any of the nucleobases) did not adsorb each water-soluble analyte. On the basis of this result, a 98% ACN solution was used during the process of conditioning and sample loading to decrease the concentration of water in the sample, which potentially inhibited the formation of hydrogen bonding between each analyte and the modified nucleobase. Considerable improvements of recoveries were observed in Adenine- and Cytosine-modified sorbents. These results were possibly attributed to the effective expression of hydrogen bonding by decreasing water concentration in the sample solution. Although a non-aqueous (100% ACN) sample solution can be expected to obtain higher recoveries compared with the 98% ACN solution, a decrease in recoveries was observed in Adenine-modified sorbent. From these results, the highest adsorption property was observed in Adenine-modified sorbent using 98% ACN as a sample condition, and the combination of this sample condition and sorbent is effective for high adsorption under HILIC condition. Moreover, we also revealed that a balance between the thickness of water layer and the modification amount of nucleobase is important for retention in the HILIC-type sorbent.

Effects of pendant-like hydrophilic monomers on the adsorption properties of reversed-phase-type sorbents for solid-phase extraction

Solid-phase extraction (SPE) has been extensively employed as a pretreatment method. In SPE, reversed-phase-type sorbents have been widely applied for the pretreatment of environmental or biological samples. Hydrophilic-lipophilic balance (HLB)-type sorbents, constituting the copolymers used as reversed-phase-type sorbents, have been applied for various sample pretreatment methods. In HLB-type sorbents, the hydrophilic monomer contributes to the improved wettability of sorbents and increase of polar interactions. In this study, three pendant-like hydrophilic monomers, viz. N-vinylpyrrolidone (NVP), 4-acryloylmorpholine (AMO), and 4-vinyl-1,3-dioxolan-2-one (VDO), respectively, exhibiting different Log P values and possibly causing different polar interactions, were selected to improve the adsorption properties of polar compounds, and divinylbenzene (DVB)-based HLB-type sorbents containing each hydrophilic monomer were synthesized and examined. By the optimization of the molar ratio of DVB and the hydrophilic monomer (i.e. HLB), the inert diluent, and the degree of cross-linking, the developed sorbents exhibited higher recoveries for various polar compounds (viz. cytosine, uracil, cytidine, uridine, 2'-deoxycytidine, 2'-deoxyguanosine, adenine, thymidine, adenosine, and 2'-deoxyadenosine) compared to commercially available HLB-type sorbents.