Application of solid phase extraction with the use of silica modified with polyaniline film for pretreatment of samples from plant material before HPLC determination of triterpenic acids

Polyaniline-silica doped with oxalic acid as a novel extractor phase in thin film solid-phase microextraction for determination of hormones in urine

In this study, different polyanilines were synthesized and evaluated for the determination of three hormones, including 17-β-estradiol, 17-α-ethinylestradiol, and estrone, in urine using a novel methodology based on thin film solid-phase microextraction technique, employing the sampling well plate system. The extractor phases, designated as polyaniline doped with hydrochloric acid, polyaniline doped with oxalic acid, polyaniline-silica doped with hydrochloric acid, and polyaniline-silica doped with oxalic acid, were characterized by electrical conductivity measurements, scanning electron microscopy, and Fourier transform infrared spectroscopy. The optimized extraction conditions were composed of 1.5 mL of urine and pH adjusted to 10, with no need to dilute sample and the desorption step, 300 μL of acetonitrile was used. The calibration curves were performed in the sample matrix, with detection and quantification limits ranged from 0.30 to 3.03 μg L-1 and from 1.0 to 10.0 μg L-1 , respectively, with r ≥ 0.9969. The relative recoveries ranged from 71% to 115%, and intraday precision showed values ≤12% and interday ≤20%. The applicability of the method was successfully evaluated, and six urine samples from female volunteers were analyzed. The analytes were not detected or were below the limits of quantification in these samples.

Polyaniline and Polyaniline-Based Materials as Sorbents in Solid-Phase Extraction Techniques

Polyaniline (PANI) is one of the best known and widely studied conducting polymers with multiple applications and unique physicochemical properties. Due to its porous structure and relatively high surface area as well as the affinity toward many analytes related to the ability to establish different types of interactions, PANI has a great potential as a sorbent in sample pretreatment before instrumental analyses. This study provides an overview of the applications of polyaniline and polyaniline composites as sorbents in sample preparation techniques based on solid-phase extraction, including conventional solid-phase extraction (SPE) and its modifications, solid-phase microextraction (SPME), dispersive solid-phase extraction (dSPE), magnetic solid-phase extraction (MSPE) and stir-bar sorptive extraction (SBSE). The utility of PANI-based sorbents in chromatography was also summarized. It has been shown that polyaniline is willingly combined with other components and PANI-based materials may be formed in a variety of shapes. Polyaniline alone and PANI-based composites were successfully applied for sample preparation before determination of various analytes, both metal ions and organic compounds, in different matrices such as environmental samples, food, human plasma, urine, and blood.

A metal organic framework polymer monolithic column as a novel adsorbent for on-line solid phase extraction and determination of ursolic acid in Chinese herbal medicine

A metal organic framework (MOF)-polymer monolithic column was prepared by redox initiation using modified MOF and N-methylolacrylamide (NMA) as co-monomers. The obtained monolithic column was characterized by scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherm measurement. It was used as a solid phase extraction (SPE) absorbent for the online enrichment of ursolic acid (UA) by high performance liquid chromatography. The adsorption amount of UA on the monolith was compared with that of silica gel-C18 adsorbent and the monolith without MOF material. The MOF-polymer monolithic column showed high selectivity and good permeability. Under the optimum conditions for extraction and determination, the calibration equation was y = 79.854× + 0.1939; the linear range was 0.001-0.9 mg/mL; the linear regression coefficient was 0.9993; the limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 μg/mL and 0.57 μg/mL, respectively; the inter-day and intra-day accuracies were <6.44%; the recovery was in the range of 86.52-105.26%. The MOF-polymer monolithic column was successfully used as SPE column for enrichment and determination of UA in Chinese herbal medicine.

Novel nanofibers mat as an efficient, fast and reusable adsorbent for solid phase extraction of non-steroidal anti-inflammatory drugs in environmental water

Core-shell polyaniline/polyacrylonitrile nanofibers mat (PANI/Pan NFsM) was prepared for extraction of hydrophilic non-steroidal anti-inflammatory drugs (NSAIDs) in environmental water. Superior adsorption and desorption performance of PANI/Pan NFsM was confirmed by both static and dynamic adsorption/desorption experiments. These properties proved PANI/Pan NFsM was a potentially efficient and fast solid phase extraction (SPE) adsorbent for NSAIDs. Under the optimized conditions, only 3 mg of PANI/Pan NFsM could easily extract eight target analytes in 10 mL of water sample without any pre-treatment, and the analytes retained on NFsM could be easily eluted by 500 μL of 1% acetic acid methanol for direct UPLC-MS/MS analysis. In addition, each piece of PANI/Pan NFsM could be reused for at least 20 times without performance decline. Possible adsorption mechanisms were also proposed. Practical feasibility was validated through the actual sample analysis.

Protonation of polyaniline-coated silica stationary phase affects the retention behavior of neutral hydrophobic solutes in reversed-phase capillary liquid chromatography

Because of its high conductivity when acid doped, polyaniline is known as a synthetic metal and is used in a wide range of applications, such as supercapacitors, biosensors, electrochromic devices, or solar and fuel cells. Emeraldine is the partly oxidized, stable form of polyaniline, consisting of alternating diaminobenzenoid and iminoquinoid segments. When acidified, the nitrogen atoms of emeraldine become protonated. Due to electrostatic repulsion between positive charges, the polarity and morphology of emeraldine chains presumably change; however, the protonation effects on emeraldine have not yet been clarified. Thus, we investigated these changes by reversed-phase capillary liquid chromatography using a linear solvation energy relationship approach to assess differences in dominant retention interactions under a significantly varied mobile phase pH. We observed that hydrophobicity dominates the intermolecular interactions under both acidic and alkaline eluent conditions, albeit to different extents. Therefore, by tuning the mobile phase pH, we can even modulate the retention of neutral hydrophobic solutes, such as aromatic hydrocarbons, because the pH-dependent charge and structure of polymer chains of the emeraldine-coated silica stationary phase show a mixed-mode separation mechanism.

Simultaneous Determination of Oleanolic Acid and Ursolic Acid by in Vivo Microdialysis via UHPLC-MS/MS Using Magnetic Dispersive Solid Phase Extraction Coupling with Microwave-Assisted Derivatization and Its Application to a Pharmacokinetic Study of Arctiumlappa L. Root Extract in Rats

Simultaneous detection of oleanolic acid and ursolic acid in rat blood by in vivo microdialysis can provide important pharmacokinetics information. Microwave-assisted derivatization coupled with magnetic dispersive solid phase extraction was established for the determination of oleanolic acid and ursolic acid by liquid chromatography tandem mass spectrometry. 2'-Carbonyl-piperazine rhodamine B was first designed and synthesized as the derivatization reagent, which was easily adsorbed onto the surface of Fe3O4/graphene oxide. Simultaneous derivatization and extraction of oleanolic acid and ursolic acid were performed on Fe3O4/graphene oxide. The permanent positive charge of the derivatization reagent significantly improved the ionization efficiencies. The limits of detection were 0.025 and 0.020 ng/mL for oleanolic acid and ursolic acid, respectively. The validated method was shown to be promising for sensitive, accurate, and simultaneous determination of oleanolic acid and ursolic acid. It was used for their pharmacokinetics study in rat blood after oral administration of Arctiumlappa L. root extract.

Study of isomeric pentacyclic triterpene acids in traditional Chinese medicine of Forsythiae Fructus and their binding constants with β-cyclodextrin by capillary electrophoresis

In this study, a capillary zone electrophoresis (CZE) method was first developed to identify three microconstituents of isomeric pentacyclic triterpene acids (PTAs including oleanolic acid (OA), ursolic acid (UA) and betulinic acid (BA)) in Forsythiae Fructus (FF). The baseline separation of PTAs by CZE were eventually achieved in a background electrolyte (BGE) containing 50.0 mmol/L borax and 0.5 mmol/L β-cyclodextrin (β-CD) at pH 9.5 within 13.0 min. Herein, it was not only the compositions of BGE were detail investigated for rapid and good separation, but also the binding ratio and the equilibrium constants (K) for OA, UA and BA with β-CD was estimated by double reciprocal equation to well understand the separation mechanism. The proposed method allowed the LODs of PTAs were averaged at 1.50 μg/mL with UV detection (at 200 nm). The interday RSD of migration time and peak area were around 2.0 and 4.7% (n = 5), respectively. Thus, the content of PTAs in 19 FF real samples distinguished from maturation stages and geographical areas in China was quantified with the proposed method. Depending on the amount of each PTA in FF, it was demonstrated these microconstituents might benefit to identify their harvested time even qualities.

Silica Modified with Polyaniline as a Potential Sorbent for Matrix Solid Phase Dispersion (MSPD) and Dispersive Solid Phase Extraction (d-SPE) of Plant Samples

Polyaniline (PANI) is one of the best known conductive polymers with multiple applications. Recently, it was also used in separation techniques, mostly as a component of composites for solid-phase microextraction (SPME). In the present paper, sorbent obtained by in situ polymerization of aniline directly on silica gel particles (Si-PANI) was used for dispersive solid phase extraction (d-SPE) and matrix solid–phase extraction (MSPD). The efficiency of both techniques was evaluated with the use of high performance liquid chromatography with diode array detection (HPLC-DAD) quantitative analysis. The quality of the sorbent was verified by Raman spectroscopy and microscopy combined with automated procedure using computer image analysis. For extraction experiments, triterpenes were chosen as model compounds. The optimal conditions were as follows: protonated Si-PANI impregnated with water, 160/1 sorbent/analyte ratio, 3 min of extraction time, 4 min of desorption time and methanolic solution of ammonia for elution of analytes. The proposed procedure was successfully used for pretreatment of plant samples.

Polyaniline-deposited cellulose fiber composite prepared via in situ polymerization: enhancing adsorption properties for removal of meloxicam from aqueous media

Polyaniline (PAni), cellulose fiber (CF) and a PAni–CF composite, which were characterized by infrared spectroscopy, scanning electron microscopy and thermogravimetry, were investigated in adsorption studies of meloxicam (MLX) from aqueous media.

Microcrystalline cellulose based matrix solid phase dispersion microextration for isomeric triterpenoid acids in loquat leaves by ultrahigh-performance liquid chromatography and quadrupole time-of-flight mass spectrometry

An analytical procedure based on matrix solid phase dispersion (MSPD) microextration and ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry was developed for the determination of isomeric triterpenoid acids (maslinic acid, corosolic acid, oleanolic acid and ursolic acid) in loquat leaves. Microcrystalline cellulose was used for the first time as a solid sorbent in MSPD microextration. Compared with the traditional extraction methods, the proposed method possessed the advantages of shorter extraction time, and lower consumption of sample, sorbent and organic solvent. The MSPD parameters that influenced the extraction efficiency of isomeric analytes were investigated and optimized in detail. Under the optimized conditions, good linearity was obtained with correlation coefficients higher than 0.9990. The limits of detection and quantification were 19.6-51.6μg/kg and 65.3-171.8μg/kg, respectively. Meanwhile, the recoveries obtained for all the analytes were ranging from 90.1% to 107.5%. Finally, the optimized method was successfully applied for analyzing these isomeric acids in loquat leaves samples obtained from different cultivated areas.

Simultaneous determination of six triterpenic acids in some Chinese medicinal herbs using ultrasound-assisted dispersive liquid-liquid microextraction and high-performance liquid chromatography with fluorescence detection

A novel analytical method was developed for simultaneous determination of six triterpenic acids using ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) follow by high-performance liquid chromatography (HPLC) with fluorescence detection. Six triterpenic acids (ursolic acid, oleanolic acid, betulinic acid, maslinic acid, betulonic acid and corosolic acid) were extracted by UA-DLLME using chloroform and acetone as the extraction and disperser solvents, respectively. After the extraction and nitrogen flushing, the extracts were rapidly derivatized with 2-(12,13-dihydro-7H-dibenzo[a,g]carbazol-7-yl)ethyl4-methylbenzenesulfonate. The main experimental parameters affecting extraction efficiency and derivatization yield were investigated and optimized by response surface methodology (RSM) combined with Box-Behnken design (BBD). The limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.95-1.36 ng mL(-1) and 3.17-4.55 ng mL(-1), respectively. Under the optimum conditions, the method has been successfully applied for the analysis of triterpenic acids in six different traditional Chinese medicinal herbs.