Fast determination of bisphenol A in spiked juice and drinking water samples by pipette tip solid phase extraction using cobalt metal organic framework as sorbent

A cobalt metal organic framework was prepared with rapid ultrasound assisted method by treatment of cobalt nitrate with pyridine 2,6-dicarboxilic acid dissolved in ethanolic media and used as a sorbent for pipette tip solid phase extraction of Bisphenol A (BPA) and its determination in spiked juice and drinking water samples by HPLC. Parameters which influence extraction efficiency such as pH, sample volume, amount of sorbent, type and volume of eluent, and number of draw/eject cycles for extraction and elusion were tested and optimized. Results showed that best extraction efficiency could be obtained at pH 3, 150 ‎µL of sample volume, 3 mg of adsorbent and 10 ‎µL of methanol as elution solvent. Numbers of draw/eject cycles for both sample extraction and elution were 7 cycles. Limit of detection and limit of quantification of this method were 0.07 and 0.3 µg L-1, respectively, with linear dynamic range of 0.3 to 300 µg L-1 for BPA. This method was applied successfully for determination of BPA in five spiked juices and drinking water samples.               KEY WORDS: Cobalt metal organic framework, Bisphenol A, Pipette-tip solid phase extraction, Juice analysis Bull. Chem. Soc. Ethiop. 2018, 32(3), 595-602.DOI: https://dx.doi.org/10.4314/bcse.v32i3.1

High-Capacity Conductive Nanocellulose Paper Sheets for Electrochemically Controlled Extraction of DNA Oligomers

Highly porous polypyrrole (PPy)-nanocellulose paper sheets have been evaluated as inexpensive and disposable electrochemically controlled three-dimensional solid phase extraction materials. The composites, which had a total anion exchange capacity of about 1.1 mol kg−1, were used for extraction and subsequent release of negatively charged fluorophore tagged DNA oligomers via galvanostatic oxidation and reduction of a 30–50 nm conformal PPy layer on the cellulose substrate. The ion exchange capacity, which was, at least, two orders of magnitude higher than those previously reached in electrochemically controlled extraction, originated from the high surface area (i.e. 80 m2 g−1) of the porous composites and the thin PPy layer which ensured excellent access to the ion exchange material. This enabled the extractions to be carried out faster and with better control of the PPy charge than with previously employed approaches. Experiments in equimolar mixtures of (dT)6, (dT)20, and (dT)40 DNA oligomers showed that all oligomers could be extracted, and that the smallest oligomer was preferentially released with an efficiency of up to 40% during the reduction of the PPy layer. These results indicate that the present material is very promising for the development of inexpensive and efficient electrochemically controlled ion-exchange membranes for batch-wise extraction of biomolecules

Simultaneous determination of droxidopa and carbidopa by carbon paste electrode functionalized with NiFe2O4 nanoparticle and 2-(4-ferrocenyl-1,2,3triazol-1-yl)-1-(naphthalen-2-yl) ethanone

Droxidopa is a prescribed medication for the treatment of orthostatic hypertension in patients with pure autonomic failure and multiple system atrophy, which causes symptoms of lightheadedness and Parkinson's disease. In the current study, a simple electrochemical sensor designed for simultaneously determination of droxidopa and carbidopa via using 2-(4-ferrocenyl-1,2,3triazol-1-yl)-1-(naphthalen-2-yl) ethanone (2FTNE) modified NiFe2O4 nanoparticles paste electrode (2FTNENFOCPE). The 2FTNENFOCPE exhibited exceptional electrochemical catalytic behavior against droxidopa and carbidopa. Chronoamperometry, cyclic voltammetry and differential pulse voltammetry (DPV) were used to explore the analytical performance of 2FTNENFOCPE for co-detection of droxidopa and carbidopa. The 2FTNENFOCPE is able to separate oxidation peak potentials of droxidopa and carbidopa about 440 mV. The detection limits achieved via DPV, for droxidopa and carbidopa were 6.0 � 10�8 and 3.0 � 10�7 M. In the final, the 2FTNENFOCPE was utilized successfully to measure the droxidopa and carbidopa in the real solutions. © 2020 Elsevier Lt