Green protocol for the preparation of hydrophilic molecularly imprinted resin in water for the efficient selective extraction and determination of plant hormones from bean sprouts.

In this study, a novel and green synthesis of a new hydrophilic molecularly imprinted 3-aminophenol-hexamethylenetetramine (MIAPH) resin for the selective recognition and separation of plant hormones was developed. The MIAPH resin was obtained using 3-aminophenol as multifunctional monomer which introduced hydroxyl, amino, and imino groups simultaneously, and adenine was used as a dummy template for molecular imprinting. Meanwhile, hexamethylenetetramine released formaldehyde slowly through hydrolysis which was used as the cross-linking agent to avoid the direct and excessive use of toxic formaldehyde. The entire procedure was performed under mild conditions, and was facile, environmentally friendly and energy-efficient. The obtained MIAPH resin showed high specific recognition toward plant hormones and higher recoveries in bean sprouts compared to NIAPH, HLB, and C18. Various parameters affecting the extraction efficiency were optimized, and the calibration linearity of the MIAPH‒SPE‒HPLC method was determined from 0.07 to 2.86 mg kg-1 with a correlation coefficient (r) ≥ 0.9994 under the optimal conditions. Recoveries of spiked standards ranged from 90.2 to 99.1% for bean sprout with a relative standard deviation of ≤5.3%. Finally, the established MIAPH‒SPE‒HPLC method was successfully applied for the selective extraction and sensitive detection of plant hormones in a variety of complex vegetable matrices.

Molecularly imprinted phloroglucinol-formaldehyde-melamine resin prepared in a deep eutectic solvent for selective recognition of clorprenaline and bambuterol in urine.

A new molecularly imprinted phloroglucinol-formaldehyde-melamine resin (MIPFMR) was synthesized in a deep eutectic solvent (DES) using phenylephrine as a dummy template. The MIPFMR was used as a solid phase extraction (SPE) sorbent for the selective isolation and recognition of clorprenaline (CLP) and bambuterol (BAM) in urine. Phloroglucinol and melamine were used as double functional monomers that introduced abundant hydrophilic groups (such as hydroxyl groups, imino groups, and ether linkages) into the MIPFMR, making it compatible with aqueous solvents. In addition, the formation of DES by combining the quaternary ammonium salt of choline chloride with ethylene glycol as a hydrogen bond donor was an environmentally safe alternative to toxic organic solvents such as chloroform and dimethylsulfoxide that are typically used in the preparation of most molecularly imprinted polymers (MIPs). Moreover, MIPFMR-based SPE of CLP and BAM in urine resulted in higher recoveries and purer extracts than those obtained by using other SPE materials (e.g., SCX, C18, HLB, and non-imprinted phloroglucinol-formaldehyde-melamine resin (NIPFMR)). The optimized MIPFMR-SPE-HPLC-UV method had good linearity (r2 ≥ 0.9996) ranging from 15.0 to 3000.0 ng mL-1 for CLP and BAM, and the recoveries at three spiked levels ranged from 91.7% to 100.1% with RSDs ≤7.6%. The novel MIPFMR-SPE-HPLC-UV method is simple, selective, and accurate, and can be used for the determination of CLP and BAM in urine samples.

Hydrophilic Molecularly Imprinted Resorcinol-Formaldehyde-Melamine Resin Prepared in Water with Excellent Molecular Recognition in Aqueous Matrices.

Hydrophilic molecularly imprinted resorcinol-formaldehyde-melamine resin (MIRFM) is synthesized in water and shows excellent molecular recognition in aqueous matrices. The double functional monomers resorcinol and melamine, and the cross-linker formaldehyde, are all hydrophilic, and then the hydrophilic groups (such as hydroxyls, imino groups, and ether linkages) can be introduced into MIRFM, which make the material compatible with aqueous samples. The general principle is demonstrated by the synthesis of MIRFM using sulfanilamide as a dummy template for the selective recognition to sulfonamides (SAs) in milk samples. Resorcinol and melamine can interact with the template mainly by hydrogen bonding and π-π interaction, which makes MIRFM and the analytes have strong affinity. Besides, melamine can improve the rigidity of MIRFM and accelerate the polymerization process, so there is no need to add base or acid as a catalyst, which guarantees the success of molecular imprinting. MIRFM shows higher recovery and improved purification effect for SAs, in comparison to silica, HLB, C18, and SCX. Because of its excellent hydrophilicity and specificity, MIRFM is promising to be applied in biological, environmental, and clinical fields.

Ionic liquid-molecularly imprinted polymers for pipette tip solid-phase extraction of (Z)-3-(chloromethylene)-6-flourothiochroman-4-one in urine.

A new type of ionic liquid-molecularly imprinted polymers (IL-MIPs) synthesized by precipitation polymerization using 1-allyl-3-methylimidazolium bromide and acrylamide as co-functional monomers and (Z)-6-fluoro-3-(hydroxymethylene)-thiochroman-4-one (FHO) as dummy template was successfully applied as a selective adsorbent of pipette tip solid-phase extraction (PT-SPE) for rapid extraction and determination of (Z)-3-(chloromethylene)-6-flourothiochroman-4-one (CFO) in urine. The factors that affected the extraction efficiency including amounts of adsorbent, types of washing solvent, and types and volumes of elution solvent were optimized. Under the optimum conditions of ionic liquid-molecularly imprinted polymers-pipette tip solid-phase extraction (IL-MIPs-PT-SPE) coupled with HPLC-UV, good linearity for CFO was achieved in a range of 0.1-10.0µgmL(-1) (r=0.9999) and the recoveries at three spiked levels were ranged from 94.8% to 103.4% with the relative standard deviations (RSDs) less than 5.7% (n=3).