Extraction of trace nitrophenols in environmental water samples using boronate affinity sorbent

Theoretical study and analysis of o-nitrophenol adsorption using layered double hydroxides containing Ca-Al, Ni-Al and Zn-Al

A theoretical assessment of the o-nitrophenol adsorption on layered double hydroxides containing different metallic species (Ca-Al, Ni-Al and Zn-Al) was performed. Experimental o-nitrophenol adsorption isotherms obtained at different adsorption temperatures with these layered double hydroxides were analyzed using a statistical physics monolayer model. Model calculations showed that the o-nitrophenol aggregation could occur with a high degree. It was estimated that the o-nitrophenol adsorption implied a non-flat orientation on all adsorbent surfaces and this process was multi-molecular. It was also demonstrated that there was no significant difference on the o-nitrophenol adsorption capacities of tested adsorbents, which varied from 77 to 135, 95 to 122 and 74 and 130 mg/g for Ca-Al, Ni-Al and Zn-Al layered double hydroxides, respectively. This finding suggested that the incorporation of Ca-Al, Ni-Al and Zn-Al in the layered double hydroxide structure played a similar role to adsorb o-nitrophenol molecules from aqueous solution. Calculated adsorption energies and thermodynamic functions confirmed an exothermic adsorption with the presence of physical-based interaction forces. This paper highlights the importance of reliable theoretical calculations based on statistical physics theory to contribute in the understanding of the adsorption mechanisms of a relevant water pollutant using layered double hydroxides as promising adsorbents for industrial applications.

Stir bar sorptive extraction and its application

Recent progress of stir bar sorptive extraction (SBSE) in the past six years is reviewed. The preparation methods including electrodeposition, self-assembly, solvent exchange, physical magnetic adsorption and electrostatic spinning, for the coated stir bar are summarized and compared, specifically for a specific material for coatings fabrication, e.g., carbon-based materials and metal organic frameworks. The emerging materials (e.g., graphene, graphene oxide, carbon nanotubes, monolith, metal-organic frameworks and porous organic polymers) applied for coated stir bar fabrication are one of the focus of this review, along with their respective advantages in extraction process and application in trace analysis. The development and application of extraction apparatus of SBSE are also involved. Based on these information, the development status and prospects of SBSE as an efficient sample pretreatment technique in real sample analysis are discussed.

Organic Boronate Affinity Sorbent for Capture of cis-Diol Containing Compounds Eman Alzahrani

Boronate affinity chromatography (BAC) is argued to be a critical tool in specific capture and separation of cis-diol containing compounds. In present study, organic boronate affinity monolith poly(3-acrylamido phenylboronic acid-co-ethylene dimethacrylate) (AAPBA-co-EDMA) is prepared through one-step in situ polymerization procedure within a micropipette through the application of a pre-polymerization mixture which contains functional monomer (3-acrylamido phenylboronic acid), cross-linker (ethylene dimethacrylate), porogenic solvent (methanol with poly ethylene glycol) and initiator (2,2-dimethoxy-2-phenyl-acetophenone). Following the optimization of time exposure to UV lamp with 365 nm, the macroporous organic boronate monolith was selected. Several approaches including SEM and BET analysis, FT-IR spectroscopy and measuring contact angle were applied in the characterization of the morphology of the monolith. Several cis-diol compounds that include catechol and galactose are applied in the assessment of the boronate affinity of the organic monolithic material. Additionally, the capture of glucose from urine sample is also conducted. The basic principle of the approach is that boronic acid forms covalent bond with cis-diols in basic solutions whereas the ester bonds are dissociated under acidic media. By using the study results, monolith demonstrate good selectivity towards cis-diol containing compounds. Due to the hydrophilic property of monolith, the affinity chromatography monolith can be performed for several cis-diol compounds including glycoproteins and nucleosides. Also, fabrication of the organic boronate monolithic in microfluidic equipment is essential in facilitating the extraction of boronate affinity using small-volume samples.

Simultaneous Determination of 2-Nitrophenol and 4-Nitrophenol in Pharmaceutical Industrial Wastewater by Electromembrane Extraction Coupled with HPLC-UV Analysis

Background: In the present study, an electromembrane extraction (EME) followed by a simple high performance liquid chromatography with ultraviolet detection (HPLC-UV) was developed and validated for simultaneous determination of 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP) in pharmaceutical industrial wastewater sample. Main parameters of electromembrane extraction were evaluated and optimized. Methods: 1-octanol was immobilized in the pores of a polypropylene hollow fiber as supported liquid membrane. As a driving force, a 100 volt electrical voltage was applied to transfer the analytes from the sample solution (pH, 7.5) through the supported liquid membrane into an acceptor solution (pH, 12). Results: The best enrichment factors were obtained 36 and 72 for 2-NP and 4-NP, respectively after 15 minutes of extraction. The effect of carbon nanotube, as a solid nano-sorbent on EME efficiency, was also evaluated. The proposed method provided the linearity in the range of 10-1000 ng/mL for 2-NP (R2> 0.9997) and 4-NP (R2> 0.9999) with repeatability range (% RSD) between 2.6-10.3 % (n = 3). The limit of detection was 3 ng/mL and the limit of quantitation was 10 ng/mL. Conclusion: Finally, the method was applied for the determination of 2-NP and 4-NP in industrial wastewater samples with relative recoveries in the range between 67–76 %. EME improved the sensitivity of HPLC-UV for the determination of trace concentrations of these analytes.