Nahid Heidari

A solid-phase microextraction platinized stainless steel fiber coated with a multiwalled carbon nanotube-polyaniline nanocomposite film for the extraction of thymol and carvacrol in medicinal plants and honey.

A mechanically hard and cohesive porous fiber, with large surface area, for more strong attachment of the coating was provided by platinizing a stainless steel wire. Then, the platinized stainless steel fiber was coated with a multiwalled carbon nanotube/polyaniline (MWCNT/PANI) nanocomposite using electrophoretic deposition (EPD) method and applied for the extraction of thymol and carvacrol with direct-immersion solid-phase microextraction (DI-SPME) method followed by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) quantification. To provide a larger coarse surface for the tightened attachment of coating on the fiber, a stainless steel wire was platinized using a suitable optimized EPD method. Different experimental parameters were studied and the optimal conditions were obtained as: pH of the sample solution: 2; extraction time: 60min; salt content in the sample solution: 1% w/v NaNO3; desorption time: 60min; type and volume of the desorption solvent: acetonitrile, 100μL. Under the optimized conditions, limits of detection (LODs) were 0.6 and 0.8μgmL(-1) for thymol and carvacrol, respectively. Linear dynamic range (LDR) for the calibration curves of both analytes were 1-80μgmL(-1). Relative standard deviation (RSD%, n=6) was 6.8 for thymol and 12.7 for carvacrol. The proposed fiber was successfully applied for the recovery and determination of thymol and carvacrol in thyme, savory, and honey samples.

Highly sensitive and selective determination of uranium in natural waters through a novel solidified floating organic drop microextraction method coupled with spectrophotometric determination

Ultra trace amounts of uranyl ions were extracted using a reliable, simple and selective solidified floating organic drop microextraction (SFODME) method, and determined by UV-Vis spectrophotometry. Di-2-ethylhexylphosphoric acid (HDEHP) was applied as the complexing ligand during the microextraction process, and Arsenazo III (AIII) was used as the chromogenic reagent through spectrophotometric determination. The effects of important experimental parameters on the formation of UO2–AIII complex and color development were studied. Other important experimental parameters affecting microextraction recovery such as type and volume of extracting organic solvent, acid concentration of sample solution, ligand concentration, stirring rate, extraction time and temperature, and salt addition were also evaluated and optimized. Under the optimized conditions, a linear response was obtained over the range of 0.8–75 ng mL−1 for uranyl ions. The interfering effect of some foreign ions on the extraction and determination of uranyl ions was also investigated. Limit of detection, relative standard deviation and enrichment factor of the proposed SFODME-UV method were obtained as 0.1 ng mL−1, 3.7% and 125, respectively, for uranyl ions. The proposed method was applied successfully for the extraction and determination of uranyl ions in natural water samples. The results of the proposed SFODME method and those reported by official standard method were in good agreement.

A high area, porous and resistant platinized stainless steel fiber coated by nanostructured polypyrrole for direct HS-SPME of nicotine in biological samples prior to GC-FID quantification.

The surface of a stainless steel fiber was made porous, resistant and cohesive using electrophoretic deposition and coated by the nanostructured polypyrrole using an amended in-situ electropolymerization method. The coated fiber was applied for direct extraction of nicotine in biological samples through a headspace solid-phase microextraction (HS-SPME) method followed by GC-FID determination. The effects of the important experimental variables on the efficiency of the developed HS-SPME-GC-FID method, including pH of sample solution, extraction temperature and time, stirring rate, and ionic strength were evaluated and optimized. Under the optimal experimental conditions, the calibration curve was linear over the range of 0.1-20μgmL-1 and the detection limit was obtained 20ngmL-1. Relative standard deviation (RSD, n=6) was calculated 7.6%. The results demonstrated the superiority of the proposed fiber compared with the most used commercial types. The proposed HS-SPME-GC-FID method was successfully used for the analysis of nicotine in urine and human plasma samples.

Iron oxide/silica/polypyrrole nanocomposite sorbent for the comparison study of direct-immersion and headspace solid-phase microextraction of aldehyde biomarkers in human urine

Graphical abstract Figure. No caption available. HighlightsFe3O4/SiO2/PPy nanocomposite was synthesized, characterized and coated onto a steel wire as a reliable SPME fiber coating.The fiber was used for HS‐ and DI‐SPME‐GC‐FID analysis of endogenous aldehydes in human urine, without derivatization.The methods showed good RSDs, wide LDRs and low LODs, while HS‐SPME‐GC‐FID found to be more sensitive and precise. ABSTRACT The short chain alkyl aldehydes, especially hexanal and heptanal, in urine are considered as potential biomarkers of several diseases and their determination in biological fluids has gained a great attention in recent years. Magnetic iron oxide core‐shell silica (Fe3O4/SiO2) nanoparticles was synthesized and embedded in polypyrrole (PPy) during the in‐situ electropolymerization on the surface of a stainless‐steel wire. The Fe3O4/SiO2/PPy coated steel wire was used as a novel and effective solid‐phase microextraction (SPME) fibre. It was employed for the extraction and preconcentration of hexanal and heptanal through direct‐immersion (DI‐) and headspace (HS‐) SPME sampling strategies, followed by GC‐FID quantification. The prepared nanocomposite fiber was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT‐IR). All influential variables on the extraction efficiency of the DI‐ and HS‐SPME sampling modes were studied and optimized. The calibration curves showed acceptable linearity (R2 > 0.99) over the range of 0.01–10 &mgr;g mL−1 for the DI‐SPME‐GC‐FID and 0.01–15 &mgr;gmL‐1 for HS‐SPME‐GC‐GID methods. The limit of detections (LODs) corresponding to the analytes amounts for which signal‐to‐noise ratios were equal to 3, estimated to be 0.1 and 0.5 ng mL‐1, for hexanal and heptanal using HS‐SPME‐GC‐FID, respectively. The LODs for DI‐SPME‐GC‐FID method were 0.1 and 1.0 for hexanal and heptanal. For six replicated analyses of 0.5 &mgr;g mL‐1 of the analytes, the relative standard deviations (RSDs) were calculated 6.5–6.6% and 5.1–5.3%, for DI‐SPME and HS‐SPME, respectively. The two developed methods were successfully applied for analysis of hexanal and heptanal in urine samples without derivatization step. The HS‐SPME‐GC‐FID sampling/determination strategy showed better analytical figures of merit and longer lifetime for the prepared nanocomposite fiber.

Comparison of the Conventional and Electroenhanced Direct-Immersion Solid-Phase Microextraction for Sampling of Nicotine in Biological Fluids of the Human Body

A stainless steel fiber was made porous and adhesive by platinization and then coated by nanostructured polypyrrole (PPy), using an appropriate electrophoretic deposition (EPD) method. The morphological surface structure and functional groups of the PPy-coated fiber were studied using SEM (Scanning electron microscope) instrument. The prepared fiber was used for comparison of direct immersion (DI) and electroenhanced direct immersion solid-phase microextraction (EE-DI-SPME) of nicotine in human plasma and urine samples followed by gas chromatography flame ionization detector (GC-FID) determination. The effects of the influential experimental parameters on the efficiency of the DI-SPME and EE-DI-SPME methods, including the pH and ionic strength of the sample solution, applied Direct current (DC) voltage, extraction temperature and time and stirring rate, were optimized. Under the optimal conditions, the calibration curves for the DI-SPME-GC-FID and EE-DI-SPME-GC-FID methods were linear over the ranges of 0.1–10.0 μg mL−1 and 0.001–10.0 μg mL−1, respectively. The relative standard deviations (RSDs, n = 6) were found to be 6.1% and 4.6% for the DI and EE strategies, respectively. The LODs (limit of detection) of the DI-SPME-GC-FID and EE-DI-SPME-GC-FID methods were found to be 10 and 0.3 ng mL−1, respectively. The relative recovery values (for the analysis of 1 µg mL−1 nicotine) were found to be 91–110% for EE-DI-SPME and 75–105% for DI-SPME. The enrichment factors for DI-SPME and EE-DI-SPME sampling were obtained as 38,734 and 50,597, respectively. The results indicated that EE-SPME was more efficient for quantitation of nicotine in biological fluids. The developed procedure was successfully carried out for the extraction and measurement of nicotine in real plasma and urine samples.