Polypyrrole monolithic extraction phase: From conventional to miniaturized sample preparation techniques

Molecularly imprinted polymers in online extraction liquid chromatography methods: Current advances and recent applications

BACKGROUND

One of the primary objectives in green analytical practices is the seamless integration of extraction and separation steps, resulting in the augmentation of both analytical throughput and method performance. Consequently, the exploration of prospective sorbent materials has drawn significant attention in the scientific community, particularly concerning the potential for online procedures. Employing the optimal sorbent material within an automated analytical approach holds the promise of elevating the precision of the analytical evaluation. Molecularly imprinted polymers (MIPs) excel in specific analyte interaction within complex matrices. However, MIPs' full potential was not widely exploring especially for online analytical methodologies.

RESULTS

Here is presented a comprehensive overview of the current applications of MIPs as sorbent materials within integrated and automated separation methodologies applied to diverse matrices including biological, food, and environmental samples. Notably, their primary advantage, as evidenced in the literature, lies in their exceptional selectivity for the target analyte discussed according to the adopted synthesis protocol. Furthermore, the literature discussed here illustrates the versatility of MIPs in terms of modification with one or more phases which are so-called hybrid materials, such as molecularly imprinted monoliths (MIM), the molecularly imprinted ionic liquid polymer (IL-MIP), and restricted access to molecularly imprinted polymer (RAMIP). The reported advantages enhance their applicability in integrated and automated separation procedures, especially to the column switching methods, across a broader spectrum of applications.

SIGNIFICANCE

This revision aims to demonstrate the MIP's potential as a sorbent phase in integrated and automated methods, this comprehensive overview of MIP polymers in integrated and automated separation methodologies can be used as a valuable guide, inspiring new research on developing novel horizons for MIP applications to have their potential emphasized in analytical science and enhanced to the great analytical methods achievement.

Restricted access polypyrrole employed in pipette-tip solid-phase extraction for determination of nimodipine and nicardipine in breast milk

A HPLC-UV method for the determination of nimodipine and nicardipine in breast milk using restricted access polypyrrole as an adsorbent in pipette-tip solid-phase extraction (PT-SPE) has been developed. The chromatographic conditions were a C₁₈ column (150 mm × 4.60 mm, 5 μm) using methanol : acetonitrile : ultrapure water (55 : 30 : 15, v/v/v) at a flow rate of 1.0 mL min^-1 and detection at 236 nm. The adsorbents have been synthesized and characterized by using Fourier-transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, surface analysis, wettability and point zero charge, and were then applied in sample preparation. The main parameters that affect analyte recovery from breast milk by PT-SPE were optimized and the analytical method showed recoveries around 100%, linearity from 3 to 3000 ng mL^-1, and correlation coefficients (r) ≥ 0.99 for the two analytes, in addition to adequate precision, accuracy and robustness. Finally, the validated method has been successfully applied in analyses of breast milk from volunteers.

Molecularly imprinted monolith-based portable in-tip microextraction device for field specific extraction of triazine herbicides in aqueous samples followed by chromatographic quantification

Field selective extraction is crucial for accurate monitoring of triazine herbicides (TAHs) in aqueous samples. For this purpose, using atrazine as template and 3-acrylamido phenylboronic acid as functional monomer which was quickly screened with calculation simulation technology, a new molecularly imprinted monolith-based adsorbent (MBA) was fabricated and utilized as the extraction phase of laboratory-made multichannel in-tip microextraction device (MIMD). A series of techniques were adopted to characterize the physical and chemical properties of the synthesized MBA. Under the optimized preparation conditions, the recognition factor and capture capacity of MBA towards atrazine were as high as 2.9 and 23.4 mg/g, respectively, and the enrichment factors towards TAHs located in the range of 276-359. The study about adsorption isotherm evidenced the adsorption of MBA towards atrazine was fit for Freundlich adsorption model. Under the beneficial extraction parameters, the introduced MBA/MIMD was utilized to on-site extract TAHs in a variety of aqueous samples prior to HPLC determination. High sensitivity (limit of detection: 0.25-0.64 ng/L), good precision (relative standard deviation: 1.4-9.5%) and satisfying recovery (81.0-113%) were achieved. Accuracy and reliability of the introduced method were inspected through confirmation experiments. Owing to the good results and outstanding merits, the established MBA/MIMD technique is appropriate for field sample preparation of TAHs and the developed method can be utilized to monitor TAHs residuals in various aqueous samples.

A miniaturized analytical method based on molecularly imprinted absorbents for selective extraction of (S)-1,1'-binaphthyl-2,2'-diamine and combinatorial screening of polymer precursors by computational simulation

Chiral resolution of binaphthylamine is often a toilful conundrum in the field of analytical chemistry and biomedicine. The work puts forward a selective, sensitive, and miniaturized analytical method based on molecularly imprinted polymers (MIPs) as adsorbent for miniaturized tip solid-phase extraction (MTSPE) in the separation of binaphthylamine enantiomer. This method combines the advantages of MIPs (high selectivity), MTSPE (low consumption), and high-performance liquid chromatography (HPLC, high sensitivity). A simple synthesis methodology of MIP (P2) was conducted through bulk polymerization with (S)-(-)-1,1'-binaphthyl-2,2'-diamine (S-DABN) as template together with methacrylic acid monomer, and ethylene glycol dimethacrylate as cross-linker in proper porogen, realizing a selective recognition and efficient enrichment for S-DABN. The method exhibited appreciable linearity (0.06-1.00 mg ml^-1 ), low quantification limit (0.056 mg ml^-1 ), good absolute recoveries (45.70%-69.29%), and high precision (relative standard deviations ≤ 3.54%), along with low consumption (0.50 ml sample solution and 25.0 mg adsorbent). Based on the density functional theory, computational simulation was used to make a preliminary prediction for rational design of MIPs and gave a reasonable elaboration involving the potential mechanism of templates interacting with functional monomers. The adsorption kinetics and thermodynamics were investigated to evaluate the recombination process of substrates. In addition, the selectivity of MIPs for S-DABN was obtained by MIP-MTSPE coupled with HPLC, which supports the feasibility of this convenient design process. The proposed method was employed for selective extraction of S-DABN and exhibited promising potential in the application of chiral analysis.