A (-)-norephedrine-based molecularly imprinted polymer for the solid-phase extraction of psychoactive phenylpropylamino alkaloids from Khat (Catha edulis Vahl. Endl.) chewing leaves.

A molecularly imprinted polymer (MIP) was prepared using (-)-norephedrine as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker and chloroform as the porogen. The MIP was used as a selective sorbent in the molecularly imprinted solid-phase extraction (MIP-SPE) of the psychoactive phenylpropylamino alkaloids, norephedrine and its analogs, cathinone and cathine, from Khat (Catha edulis Vahl. Endl.) leaf extracts prior to HPLC-DAD analysis. The MIP was able to selectively extract the alkaloids from the aqueous extracts of Khat. Loading, washing and elution of the alkaloids bound to the MIP were evaluated under different conditions. The clean baseline of the Khat extract obtained after MIP-SPE confirmed that a selective and efficient sample clean-up was achieved. Good recoveries (90.0-107%) and precision (RSDs 2.3-3.2%) were obtained in the validation of the MIP-SPE-HPLC procedure. The content of the three alkaloids in Khat samples determined after treatment with MIP-SPE and a commercial Isolute C18 (EC) SPE cartridge were in good agreement. These findings indicate that MIP-SPE is a reliable method that can be used for sample pre-treatment for the determination of Khat alkaloids in plant extracts or similar matrices and could be applicable in pharmaceutical, forensic and biomedical laboratories. Copyright © 2015 John Wiley & Sons, Ltd.

Perspectives on the Development of Filter Media for Point of Use Water Filters: Case Study of Arsenate Removal.

The demand for access to clean water will continue to increase as the world population increases. For sustainable development and embracement of technological advancement, it is plausible to consider a filter material development approach that uses locally abundant natural resources as the raw material and nanotechnology techniques for material fabrication. The review and research paper will present a perspective of the authors on how to embrace nanotechnology for filter media development with key focus on the remediation of arsenate. Drinking water contaminated with arsenic is an emerging global challenge. Continuous exposure to drinking water with high levels arsenic could result in several types of cancer. With this in mind, the US EPA in 2001 set 10 ppb as the maximum contaminant level of arsenic from the initial 50 ppb. Therefore, arsenic remediation is key in mitigating these health risks in people residing near water bodies with elevated arsenic levels. Adsorption is considered to be the cheapest. However, from literature, majority of the adsorbents cannot be used in field applications due to challenges associated with low adsorption capacity and a high level of particle leaching into purified water thus posing health dangers. Therefore, it means that many of these adsorbents are economically non-viable. A new chitosan, aluminium, titanium, iron and zirconium (CTS-Al-Ti-Fe-Zr) hybrid was fabricated through the sol-gel process. The material was characterized by scanning electron microscopy, Brunauer-Emmett-Teller and Fourier Transform Infrared spectroscopy before and after adsorption. Batch adsorption properties towards As(V) were separately studied as a function of the effect of adsorbent dose, pH, initial concentration, contact time and competing ions. Characterization results show that the material is a polycrystalline with a specific surface area of 56.4 m2g-1. Further, FTIR and SEM-EDAX showed adsorption of arsenate on the surface of the nanocomposite. Research findings suggest that with only 100 mg of the adsorbent arsenate can be reduced to less than 10 ppb from an initial concentration of 300 ppb respectively. The maximum adsorption capacity for arsenate removal was recorded as 123 mg/g. The presence of SiO3 2-, CO3 2-, and HCO3 - ions resulted in a slight decline in the adsorption efficiency of arsenate. The equilibrium data fitted well with the Langmuir isotherm 0.99518. Data from the fabricated prototype Point-of-use filter showed that with 60.0 g of the nanocomposite, it is possible to reduce 650 L of drinking water with an arsenate initial concentration of 300 ppb to less 10 ppb. In conclusion, the research findings suggest that the nanocomposite material is capable of removal of arsenate from contaminated drinking water to WHO acceptable levels with a potential to be up scaled for commercial applications.

Electrospun nanofibers as sorbent material for solid phase extraction.

Electrospinning has emerged as the most versatile technique for nanofiber fabrication. Owing to their large surface area to volume ratio, electrospun nanofibers have the potential to serve as a good sorbent material for solid phase extraction (SPE) based techniques. The ability to incorporate a variety of functionalities prior or post-electrospinning presents a platform to tune the sorbents for specific applications. It is the aim of this contribution to highlight some of the recent developments that harness the great potential of electrospun nanofibers as sorbents for SPE. The review discusses the various ways in which the electrospinning technique addresses two important parameters for sorbent material, which are sorptive capacity and selectivity. It concludes by presenting and discussing the potential for development of SPE format technology and configurations based on electrospun nanofibers.

Application of Nanofiber-packed SPE for Determination of Urinary 1-Hydroxypyrene Level Using HPLC.

It is always desirable to achieve maximum sample clean-up, extraction, and pre-concentration with the minimum possible organic solvent. The miniaturization of sample preparation devices was successfully demonstrated by packing 10 mg of 11 electrospun polymer nanofibers into pipette tip micro column and mini disc cartridges for efficient pre-concentration of 1-hydroxypyrene in urine samples. 1-hydroxypyrene is an extensively studied biomarker of the largest class of chemical carcinogens. Excretory 1-hydroxypyrene was monitored with HPLC/fluorescence detector. Important parameters influencing the percentage recovery such as fiber diameter, fiber packing amount, eluent, fiber packing format, eluent volume, surface area, porosity, and breakthrough parameters were thoroughly studied and optimized. Under optimized condition, there was a near perfect linearity of response in the range of 1-1000 µg/L with a coefficient of determination (r (2)) between 0.9992 and 0.9999 and precision (% RSD) ≤7.64% (n = 6) for all the analysis (10, 25, and 50 µg/L). The Limit of detection (LOD) was between 0.022 and 0.15 µg/L. When compared to the batch studies, both disc packed nanofiber sorbents and pipette tip packed sorbents exhibited evident dominance based on their efficiencies. The experimental results showed comparable absolute recoveries for the mini disc packed fibers (84% for Nylon 6) and micro columns (80% for Nylon 6), although the disc displayed slightly higher recoveries possibly due to the exposure of the analyte to a larger reacting surface. The results also showed highly comparative extraction efficiencies between the nanofibers and conventional C-18 SPE sorbent. Nevertheless, miniaturized SPE devices simplified sample preparation, reducing back pressure, time of the analysis with acceptable reliability, selectivity, detection levels, and environmental friendliness, hence promoting green chemistry.

Electrospun carbon nanofibers from polyacrylonitrile blended with activated or graphitized carbonaceous materials for improving anodic bioelectrocatalysis.

The electrospun carbon nanofibers obtained from polyacrylonitrile (PAN) and PAN blends with either activated carbon (PAN-AC) or graphite (PAN-GR) were tested as anodes using Shewanella oneidensis MR-1. Extensive physico-chemical and electrochemical characterization confirmed their formation, their fibrous and porous nature, and their suitability as electrodes. N2 adsorption measurements revealed high specific surface area (229.8, 415.8 and 485.2m(2) g(-1)) and porosity (0.142, 0.202 and 0.239cm(3)g(-1)) for PAN, PAN-AC and PAN-GR, respectively. The chronoamperometric measurements showed a considerable decrease in start-up time and more than a 10-fold increase in the generation of current with these electrodes (115, 139 and 155µAcm(-2) for PAN, PAN-AC and PAN-GR, respectively) compared to the graphite electrode (11.5µAcm(-2)). These results indicate that the bioelectrocatalysis benefits from the blending of PAN with activated or graphitized carbonaceous materials, presumably due to the increased specific surface area, total pore volume and modification of the carbon microstructure.

A review of opportunities for electrospun nanofibers in analytical chemistry.

Challenges associated with analyte and matrix complexities and the ever increasing pressure from all sectors of industry for alternative analytical devices, have necessitated the development and application of new materials in analytical chemistry. To date, nanomaterials have emerged as having excellent properties for analytical chemistry applications mainly due to their large surface area to volume ratio and the availability of a wide variety of chemical and morphological modification methods. Of the available nanofibrous material fabrication methods, electrospinning has emerged as the most versatile. It is the aim of this contribution to highlight some of the recent developments that harness the great potential shown by electrospun nanofibers for application in analytical chemistry. The review discusses the use of electrospun nanofibers as a platform for low resolution separation or as a chromatographic sorbent bed for high resolution separation. It concludes by discussing the applications of electrospun nanofibers in detection systems with a specific focus on the development of simple electrospun nanofiber based colorimetric probes.