Conductive polymers have been used as adsorbents to remove organic pollutants from aqueous samples. In this study, pristine polypyrrole (PPy) was used for the first time in the removal of potassium ...diclofenac (PD) and moxidectin (MOX) from aqueous solutions.PPy was properly characterised by scanning electron microscopy, thermogravimetric analysis, infrared spectroscopy, textural properties, wettability, and point zero charge. Through the characterisation results, it was observed that the adsorbent showed be favourable to adsorption, high temperature of thermal degradation, bands characteristic of the PPy,mesopore structures, and hydrophilicity. The results pointed that pH 6 favoured the removal, reaching percentages of 95.26% for PD and 99.75% for MOX.The kinetic data followed the model of pseudo second-order (PD: R
2
= 0.872 and MOX: R
2
= 0.887) with equilibrium reached in 20 min for PD and MOX. OThe best fit isotherm model was the dual-site Langmuir-Freundlich (R
2
> 0.99), with maximum capacity adsorption of 221.23 mg g
−1
for PD and 87.46 mg g
−1
for MOX. Finally, the thermodynamic study showed that the adsorption process was spontaneous and endothermic. Through the reuse study, it was possible to show a good cost-benefit ratio when using the developed adsorbent material, since it can be used several times without losing its adsorption capacity. Finally, PPy showed great potential to be used in the adsorption of compounds with different physicochemical properties.
This work reviews the literature of chiral capillary electrokinetic chromatography from January 2016 to March 2021. This is done to explore the state-of-the-art approach and recent developments ...carried out in this field. The separation principle of the technique is described and supported with simple graphical illustrations, showing migration under normal and reversed polarity modes of the separation voltage. The most relevant applications of the technique for enantioseparation of drugs and other enantiomeric molecules in different fields using chiral selectors in single, dual, or multiple systems are highlighted. Measures to improve the detection sensitivity of chiral capillary electrokinetic chromatography with UV detector are discussed, and the alternative aspects are explored, besides special emphases to hyphenation compatibility to mass spectrometry. Partial filling and counter migration techniques are described. Indirect identification of the separated enantiomers and the determination of enantiomeric migration order are mentioned. The application of Quality by Design principles to facilitate method development, optimization, and validation is presented. The elucidation and explanation of chiral recognition in molecular bases are discussed with special focus on the role of molecular modeling.
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•Magnetic mesoporous molecularly imprinted polymer was successfully synthetized, characterized and applied as adsorbent.•This new adsorbent provided recoveries around 100% and limit ...of quantification of 5.0 ng mL−1 for azamethiphos and chlorpyrifos.•New magnetic solid phase extraction coupled to HPLC-UV method is found to be simple, fast and selective.•The method was properly applied to analysis of real water and grape samples.
A magnetic mesoporous molecularly imprinted polymers was synthesized on the surface of magnetic nanoparticles silanized with 3-(trimethoxysilyl) propyl methacrylate to introduce reactive methacrylate groups. Subsequently, methacrylic acid monomers were grafted onto the surface of this adsorbent functionalized via polymerization by precipitation. Magnetic mesoporous molecularly imprinted polymer was properly characterized by different techniques and applied as adsorbent in magnetic solid phase extraction for selective determination of two organophosphorus pesticides, azamethiphos and chlorpyrifos, in mineral water and grape samples. After sample preparation optimization, recoveries of 99.56% and 98.86% were obtained for azamethiphos and chlorpyrifos, respectively. The magnetic solid phase extraction coupled to HPLC-UV presented limit of quantification of 5 ng mL−1, linearity ranged of 5 to 1000 ng mL−1, in addition to adequate accuracy, precision and robustness. The pesticides showed stability in the matrix and were satisfactorily quantified in real mineral water and grape samples.
A new selective adsorbent based on magnetic molecularly imprinted conducting polymer was firstly synthetized and applied to the magnetic solid phase extraction (MSPE) for the determination of PZQ ...enantiomers in milk samples. The enantioselective separation was performed on a Chiralpak® IB column using mobile phase composed of ultrapure water : tetrahydrofuran : diethylamine (65 : 35 : 0.05, v/v/v). After MSPE optimization, in which a magnetic molecularly imprinted polypyrrole (MMIPPy) was used as adsorbent, the best conditions were: 500 μL of acetonitrile as eluent, 75 mg of MMPPy, 1000 μL of milk sample (pH adjusted to 6.5.). The analyses showed recoveries/relative standard deviation (RSD%) 79.7 ± 2.5 and 81.1 ± 2.2 for (R)-(-)-PZQ and (S)-(+)-PZQ, respectively. By computational study carried out on the molecular design of the synthesized MMIPPy, it was found that the formation of four hydrogen bonds and one π-π stacking interaction explain the formation of the PZQ-pyrrole pre-polymerization complex at the molecular level. From the analytical validation, the developed method showed to be linear in the concentration range of 0.01 to 10 μg mL-1, with correlation coefficient larger than 0.98 and RSD% values below 15%. The LOQ obtained was 0.01 μg mL-1 for both enantiomers, with RSD% and relative error below 20%. The method was successfully applied in real sheep milk samples from various local suppliers. Finally, the results showed that MMIPPy in MSPE is an economical, simple and easy-to-perform technique.
Rationale
Ambient mass spectrometry techniques are much required in forensic chemistry to evaluate evidence with low analytical interference, high confidence, and accuracy. However, traditional ...methodologies, such as paper spray ionization, have been shown to present low sensitivity in the analysis of illicit drugs from biological matrices.
Methods
Fiber spray ionization mass spectrometry (FSI‐MS) was developed using a capillary polypropylene (PP) hollow fiber. Seized samples of drugs, i.e. a tablet, blotter paper, hashish, and cocaine powder, were analyzed. Cocaine was quantified from whole urine by dipping the fiber directly into solution. FSI‐MS was tested for the analysis of a sample of urine obtained from a drug abuse suspect.
Results
The FSI(+) analysis showed the detection of different types of synthetic drugs in tablet and blotter paper samples, e.g. amphetamine, cathinones, phenethylamines, and opioids, while pure cocaine and different types of coca alkaloids were identified from cocaine powder with good sensitivity and high mass accuracy. The hashish analysis by FSI(−) revealed signals of cannabinoids, cannabinoid acids, and cannabinoid derivatives, detected mainly as M − H− ions or chlorine adducts M + Cl−. The quantification of cocaine in whole urine showed good sensitivity and precision with limits of detection and quantification of 5.16 and 17.21 ng/mL, respectively, linearity above 0.999, and relative standard deviation below 2.71%. The evaluation of seized sample of urine showed the detection of cocaine with relative ion intensity greater than 36%, as well as the metabolites benzoylecgonine and cocaethylene with a relative intensity of 1.4% and 6%, respectively.
Conclusions
The developed FSI‐MS method has the potential to be applied to forensic sample evaluation as well as to determine illicit drugs from biological matrices in toxicological analysis. The use of a capillary PP fiber has advantages as an extractor agent and ionizing substrate, and also the feature of it being dipped directly into the sample, thus preserving the integrity of the sample, which makes this a very promising ambient mass spectrometry method and relevant to forensic chemistry.
Molecularly imprinted polymers (MIP) consist of a molecular recognition technology with applicability in different areas, including forensic chemistry. Among the forensic applications, the use of MIP ...in biological fluid analysis has gained prominence. Biological fluids are complex samples that generally require a pre-treatment to eliminate interfering agents to improve the results of the analyses. In this review, we address the development of this molecular imprinting technology over the years, highlighting the forensic applications of molecularly imprinted polymers in biological sample preparation for analysis of stimulant drugs such as cocaine, amphetamines, and nicotine.
Graphical abstract
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The purpose of this study was to evaluate the effect of the adsorption of the potassium diclofenac (PD) on a pristine multiwalled carbon nanotube (pristine MWCNT) and on the composite ...formed by the addition of polypyrrole (PPy) to pristine MWCNT, named PPy/MWCNT. They were characterized by scanning electron microscopy, infrared spectroscopy, thermogravimetric analysis, Brunauer–Emmett–Teller, surface wettability and point of zero charge. The adsorption procedure of the PD in the adsorbent materials was analysed by varying some parameters. After optimization, the materials exhibited adsorption of 93.48% and 94.98%, for pristine MWCNT and PPy/MWCNT, respectively. The kinetic data were adequately adjusted to the pseudo-second-order model for the two materials. The results of the isotherm studies showed that the models that best fit the data were the dual-site Langmuir–Freundlich and Fritz-Schlunder models, presenting Q = 59.67 mg g–1 for the pristine MWCNT and Q = 229.93 mg g–1 for the PPy/MWCNT. The thermodynamic study showed that from the values of ΔH and ΔG it was possible to conclude that an endothermic and favourable adsorption process occurred during the study. It can be observed that the addition of PPy in MWCNT causes a significant improvement in the maximum adsorption capacity of pristine MWCNT.
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 C
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
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
, and correlation coefficients (
) ≥ 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.
In this work a hollow mesoporous structured molecularly imprinted polymer was synthetized and used as adsorbent in pipette‐tip solid‐phase extraction for the determination of lamivudine (3TC), ...zidovudine (AZT) and efavirenz (EFZ) from plasma of human immunodeficiency virus (HIV) infected patients by high‐performance liquid chromatography (HPLC). All parameters that influence the recovery of the pipette tip based on hollow mesoporous molecularly imprinted polymer solid‐phase extraction (PT–HM–MIP–SPE) method were systematically studied and discussed in detail. The adsorbent material was prepared using methacrylic acid and 4‐vinylpyridine as functional monomers, ethylene glycol dimethacrylate as crosslinker, acetonitrile as solvent, 4,4′‐azobis(4‐cyanovaleric acid) as radical initiator, benzalkonium chloride as surfactant, 3TC, and AZT as templates. The simultaneous separation of 3TC, AZT and EFZ by HPLC‐UV was performed using a Gemini C18 Phenomenex® column (250 mm × 4.6 mm, 5 μm) and mobile phase consisting of acetonitrile: water pH 3.2 (68:32, v/v), flow rate of 1.0 mL/min and λ = 260 nm. The method was linear over the concentration range from 0.25 to 10 μg/mL for 3TC and EFZ, and 0.05 to 2.0 μg mL−1 for AZT, with correlation coefficients larger than 0.99 for all analytes. Recovery ± relative standard deviations (RSDs %) were 41.99 ± 2.38%, 82.29 ± 1.63%, and 83.72 ± 7.52% for 3TC, AZT, and EFZ, respectively. The RSDs and relative errors (REs) were lower than 15% for intra and interday assays. The method has been successfully applied for monitoring HIV‐infected patients outside the therapeutic dosage.
An ultra-fast method for the simultaneous determination of heavy metals in Passiflora incarnata tea by capillary electrophoresis (CE) using a short-end injection combined with multivariate analysis ...was proposed. Separation was conducted by hydrodynamic injection (5 s at 0.5 psi) using the short-end injection procedure in a fused uncoated silica capillary (50 cm total length, 10.2 cm effective length, 50 µm i.d.) with separation time less than 2 min. An indirect UV detection at 214 nm was employed by using imidazole as a chromophore. The buffer used was 6 mmol/L hydroxybutyric acid (HIBA). The optimum conditions by full factorial with a central point were achieved by 18-crown-6 concentration (23.3 mmol L−1), voltage (+11.4 kV), methanol concentration (3.8%), and temperature (20 °C). The method showed good linearity (R2 > 0.998) for both Cd and Pb, inter-day precision of less than 14.49%, and an adequate limit of quantification only for Cd (LOQ < 0.5 µg mL−1 for Cd) based on the US Pharmacopeial Convention limit requirements for elemental impurities. After method validation, the method was applied to Passiflora incarnata tea samples from a local market. Furthermore, the developed method showed great potential for the determination of metals in other samples with proper sample preparation procedures.
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