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. 2020 Jan 31;25(3):629.
doi: 10.3390/molecules25030629.

Paper Strip and Ceramic Potentiometric Platforms Modified with Nano-Sized Polyaniline (PANi) for Static and Hydrodynamic Monitoring of Chromium in Industrial Samples

Saad S M Hassan  1 , Ayman H Kamel  1 , Abd El-Galil E Amr  2   3 , M Abdelwahab Fathy  1 , Mohamed A Al-Omar  2
Affiliations

Paper Strip and Ceramic Potentiometric Platforms Modified with Nano-Sized Polyaniline (PANi) for Static and Hydrodynamic Monitoring of Chromium in Industrial Samples

Saad S M Hassan et al. Molecules. .

Abstract

Screen-printed membrane sensors based on the use of paper and ceramic substrates are fabricated, characterized, and used for rapid batch and continuous monitoring of CrIII in the form of CrO42- in some industrial products and wastewater samples. Strips of paper and ceramic platforms (15 × 5 mm) were covered with conductive carbon paint and then modified with polyaniline (PANI) film, to act as an ion-to-electron transducer, followed by a drop casting of plasticized poly (vinyl chloride) (PVC) Rhodamine-B chromate membrane as a recognition sensing material. In a 5.0 mmol L-1 Trizma buffer solution of pH ~8, the fabricated paper and ceramic based membrane sensors exhibited a near Nernstian response for CrVI ion with slopes of -29.7 ± 0.5 and -28.6 ± 0.3 mV decade-1, limit of detection 2.5 × 10-5 and 2.4 × 10-6 mol L-1 (1.3-0.12 µg mL-1), and linear concentration range 7.5 × 10-3-5.0 × 10-5 and 7.5 × 10-3-1.0 × 10-5 mol L-1 (390-0.5 µg mL-1), respectively. Both sensors exhibited fast and stable potentiometric response, excellent reproducibility, and good selectivity with respect to a number of common foreign inorganic species. Impedance spectroscopy and chronopotentiometry data revealed a small resistance and a larger double layer capacitance due to the presence of the intermediate polyaniline (PAN) conductive layer. Furthermore, the formation of a water layer between the ion selective membrane (ISM) and the underlying conductor polymer and between the conducting polymer and the carbon conducting surface was greatly reduced. The developed disposable solid-contact potentiometric sensors offer the advantages of simple design, long term potential stability, flexibility, miniaturization ability, short conditioning time, and cost effectiveness that enable mass production. The sensors were successfully used for static and hydrodynamic measurements of total chromium in some leather tanning wastewater and nickel-chrome alloy samples. The results compare favorably with data obtained by atomic absorption spectrometry.

Keywords: chromiumIII assay; chronopotentiometry; impedance spectroscopy.; paper and ceramic substrates; polyaniline; potentiometric sensors.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
SEM images of the paper and ceramic substrates treated with (A) Conductive carbon; (B) Conductive carbon + polyaniline (PANI); and (C) Conductive carbon + PANI + poly (vinyl chloride) (PVC) sensing membrane.
Figure 1
Figure 1
SEM images of the paper and ceramic substrates treated with (A) Conductive carbon; (B) Conductive carbon + polyaniline (PANI); and (C) Conductive carbon + PANI + poly (vinyl chloride) (PVC) sensing membrane.
Figure 2
Figure 2
Calibration plots of paper and ceramic based chromium(VI) sensors with PANI solid contact in 5.0 mmol L−1 Trizma buffer of pH ~8.
Figure 3
Figure 3
Influence of pH on potentiometric response of: (A) Paper, and (B) ceramic based Chromium(VI) sensors with PANI solid contact.
Figure 4
Figure 4
Chronopotentiograms of paper based sensor for chromium (VI) sensors (A) with PANI as a solid contact and (B) without using PANI, applied current: +1 nA for 60 s and −1 nA for 60 s.
Figure 5
Figure 5
Potential drift due to formation of water layer between (A) paper and (B) ceramic based chromium(VI) sensors with a PANI solid contact layer and the sensing PVC membrane.
Figure 6
Figure 6
Selectivity coefficient diagrams of: (A) paper and (B) ceramic based chromium(VI) sensors with PANI solid contact using the modified separate solutions method (MSSM).
Figure 7
Figure 7
Typical transient flow-injection analysis (FIA) potentiometric signals using: (A) Paper based and (B) ceramic based chromium(VI) sensors with PANI solid contact; (Conditions: carrier solution, 5.0 × 10−3 mol L−1 Trizma buffer of pH ~8, flow rate 4.0 mL min−1; sample volume, 100 µL).
Figure 8
Figure 8
Fabrication of paper and ceramic based chromium (VI) sensors with PANI solid contact.
Figure 9
Figure 9
Flow injection setup used for determining Cr(VI) using paper and ceramic based sensors with PANI solid contact.
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