Magnetic molecularly imprinted conducting polymer for determination of praziquantel enantiomers in milk.

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.

Hollow mesoporous structured molecularly imprinted polymer as adsorbent in pipette-tip solid-phase extraction for the determination of antiretrovirals from plasma of HIV-infected patients.

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.

Pipette-tip solid-phase extraction using poly(1-vinylimidazole-co-trimethylolpropane trimethacrylate) as a new molecularly imprinted polymer in the determination of avermectins and milbemycins in fruit juice and water samples.

A simple HPLC method was developed for the determination of abamectin (ABA), eprinomectin (EPR), and moxidectin (MOX). Pipette-tip molecularly imprinted polymer solid-phase extraction (PT-MIP-SPE) using poly(1-vinylimidazole-co-trimethylolpropane trimethacrylate) as a selective adsorbent material was studied in detail, including the washing solvent, type and volume of eluent, pH, quantity of adsorbent material and sample volume. The performance criteria for linearity, sensitivity, precision, accuracy, recovery, robustness and stability have been assessed and were within the recommended guidelines. The mean extraction recoveries/relative standard deviation for ABA 1b, EPR, ABA 1a and MOX were 98.77 ±â€¯3.82%, 88.19 ±â€¯2.57%, 110.54 ±â€¯1.52% and 100.42 ±â€¯0.59%, respectively. Finally, the results proved that PT-MIP-SPE coupled to HPLC-UV is an economical, simple and easy-to-perform technique, and presented a high potential for extraction of macrocyclic lactones in mineral water and grape and juice samples.

Pipette-tip solid-phase extraction using polypyrrole as efficient adsorbent for extraction of avermectins and milbemycins in milk.

In this work, we developed a HPLC method for the multidetermination of avermectins (AVM) (abamectin-ABA 1b and ABA 1a, eprinomectin-EPR, and ivermectin-IVM) and milbemycins (moxidectin-MOX) in milk samples using polypyrrole (PPy) as adsorbent material in pipette-tip solid-phase extraction (PT-PPy-SPE). PPy was characterized by scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray diffraction and the data agreed with the literature. The sample preparation included the clean-up of the milk by protein precipitation (PP) with acetonitrile and extraction of the analytes by PT-PPy-SPE. The chromatographic method was developed in reverse phase and isocratic mode with flow rate at 1.2 mL min-1 and ultraviolet detection at 250 nm. The mobile phase composition was acetonitrile:methanol:water (55:25:20, v/v/v). The studied parameters and the optimized conditions for the sample preparation were washing solvent (300 µL water), volume and type of eluent (500 µL methanol), volume and pH of sample (1 mL and pH 10), amount of adsorbent material (50 mg PPy), and without addition of salt (NaCl). The method was linear over the concentration range from 20 to 3000 ng mL-1 with coefficients of correlation (r) ≥ 0.99 for all analytes and recoveries around 100%. The method developed and validated was used for the analyses of real milk samples from cow treated with Ivomec® (IVM 3.5%), in which were found 21.51 ± 2.94 ng mL-1 of IVM. Finally, the results proved that PT-PPy-SPE coupled to HPLC-UV was economical, simple, and easy-to-perform technique. Graphical abstract Pipette-tip solid phase extraction using polypirrole as adsorbent material for determination of avermectins and milbemycins in milk.