Molecularly Imprinted Polymer Preconcentration and Flow Injection Amperometric Determination of 4-Nitrophenol in Water

Abstract

Downloaded by [University of Otago] at 23:47 13 July 20152 Molecularly imprinted polymers are reported as selective solid-phase extraction sorbents for flow injection amperometry for the determination of 4-nitrophenol in water. A graphite pencil electrode modified with multiwalled carbon nanotubes provided good sensitivity and excellent anti-fouling properties. Solid-phase extraction cartridges containing 100 mg of imprinted polymers with a sample volume of 50 mL resulted in a preconcentration factor of 97.7, which allowed determination of 4-nitrophenol at the maximum level permitted by the United States Environmental Protection Agency (60 µg L −1 ). A linear dynamic range of 5-300 µg L −1 for 4-nitrophenol was obtained with a limit of detection of 1.5 µg L −1 . The method was employed for the determination of 4-nitrophenol in water.

Pencil Graphite Electrodes: A Versatile Tool in Electroanalysis

“…The high electrochemical reactivity of PGEs may be due to the irregular pencil graphite surface morphology which may enhance the active surface area of the electrode, whereas the edge plane sites on the surface result in a better electron transfer and a higher resistance to surface passivation [ 35 ]. Comparing voltammograms recorded on PGE with those obtained on GCE some authors attributed the higher peak intensities obtained on PGE to the clay [ 5 ] that generates a porous structure and a high specific surface area of the pencil graphite and to a good electrocatalytic effect of the pencil graphite on the electrode process of some analytes (e.g., acyclovir [ 27 ], eugenol [ 36 ], and niclosamide [ 37 ]).…”

“…1 cm of one lead end remained outside the holder, whereas at the other end a copper wire was attached [ 28 ]. In other studies a pencil lead graphite disc electrode is used, being prepared by introducing the pencil lead into a Teflon tube [ 29 , 64 – 67 ], a PVC tube [ 68 ], and a tip of a micropipette [ 35 ] or by covering its outside surface with Teflon band [ 2 , 69 ] or with a nonconductive parafilm [ 9 ] so that only the cross-sectional surface remains free. The electrical contact between the electrode and the instrument was realized through a metal wire wrapped at the other end of the pencil lead.…”

“…In order to demonstrate the modification of a surface, different techniques are used to investigate and to compare the morphology and/or the electrochemical characteristics of the respective surface and/or of the modifier, before, during, or after the modification process. For surface morphology of bare or modified PGE investigations, different techniques of electron [ 3 , 15 , 24 , 28 , 29 , 32 , 34 , 35 , 54 , 60 , 65 – 67 , 85 , 111 , 118 – 122 , 126 – 128 , 130 , 135 , 141 – 143 , 145 – 148 , 158 , 161 , 170 , 173 , 175 , 178 , 181 – 183 , 189 , 198 , 200 , 204 , 205 , 210 , 216 , 218 , 219 ] and atomic force microscopy [ 28 , 29 , 60 , 65 – 67 , 112 , 126 , 172 , 198 , 205 ] are widely used. Sometimes, scanning electron microscopy (SEM) was coupled with energy-dispersive X-ray spectroscopy analysis [ 130 , 143 , 149 , 152 , 156 , 172 , 187 , 188 , 203 – 205 ].…”

Pencil Lead as a Material for Microfluidic 3D-Electrode Assemblies

“…Although our assay only provided qualitative information, the response for concentrations as low as 1 nmol L −1 was still easily distinguishable from the background, which is well below limits of detection provided by other pencil lead devices described for this compound (1.1 µmol L −1 for the paper-based assay [ 21 ], 7.48 µmol L −1 for bismuth-modified pencil [ 32 ], 1.9 µmol L −1 for copper modified pencil electrodes [ 33 ] and 11 nmol L −1 for a multiwalled carbon nanotube/graphite pencil electrode in a flow injection system with a pre-concentration step [ 34 ]). The ability of the system to clearly discern samples with such low concentration (1 nmol L −1 ) is enough to clearly discern people suffering from pesticide poisoning (e.g., methyl parathion) in need of relocation and treatment from “no action needed” groups, including more strict norms applicable to children from 1 to 16 years of age [ 22 ].…”

Solid-phase extractions in flow analysis

“…Spectrophotometric detection was carried out after formation of the colored Zn(II) dithizonate complex, with LOD of 400 nmol L −1 and EF of 117. Other relevant applications refer to the chemiluminometric determination of isoniazid in urine (Xiong et al 2007) as well as amperometric determination of 4-nitrophenol in water (Gholivand et al 2015) and traces of cadmium in jewelry, black and green tea, tobacco and hair (Lago et al 2016). Additionally to advantages provided by the use of MIP, the performance of these procedures was improved by using MCFA, because of the independent implementation of the steps involved in sample processing.…”