Dual Sample Preconcentration for Simultaneous Quantification of Metal Ions Using Electrochemical and Colorimetric Assays

Abstract

A paper-based method for heating preconcentration (PAD-HP) has been developed for the determination of Pb 2+ , Cd 2+ , Fe 3+ , and Ni 2+ . The design of our heating system was evaluated for dual quantification of ions using electrochemical and colorimetric methods simultaneously. The PAD-HP was used to detect Pb 2+ and Cd 2+ by anodic stripping voltammetry and to detect Fe 3+ and Ni 2+ by colorimetric reactions. Assay conditions were optimized by evaluating performance when changing the concentration of the colorimetric reagent, eluent volume, electrolyte concentration, and electrochemical parameters. Limits of detection (LOD) were determined to be 0.97 and 2.33 μg L −1 for Pb 2+ and Cd 2+ (via voltammetry) and 0.03 and 0.04 mg L −1 for Fe 3+ and Ni 2+ (via colorimetric assay), respectively. The relative standard deviations for assays were in the range of 5.76 to 10.12%. We observed that the PAD-HP method significantly enhanced the signal of all metals ions (14−100-fold, depending on the metal) in comparison to paper-based devices that did not use a heating preconcentration system. This PAD-HP method was successfully applied to the determination of metals ions in samples of drinking water, tap water, pond water, and wastewater. These results suggest that our approach can provide a convenient strategy to monitor aqueous samples for heavy metals with high sensitivity and selectivity.

Logarithmic Data Processing Can Be Used Justifiably in the Plotting of a Calibration Curve

“…Similar to conductometric analysis, data processing and analysis of the results can follow different presentations and obtain different function relationships. 21,22 It should be noted that in electrolytic analysis and coulometry, the charge C-rate is also expressed in logarithmic form. 23 In the generation of electrochemical signals, in various electroanalytical methods, the data can be expressed in a variety of ways in order to obtain a more serviceable functional relationship for result analysis.…”

“…Voltammetry and polarography are based on the measurement of current–potential curves obtained through the electrolysis of dilute solutions of target analytes. Similar to conductometric analysis, data processing and analysis of the results can follow different presentations and obtain different function relationships. , …”

Single-Use Fluidic Electrochemical Paper-Based Analytical Devices Fabricated by Pen Plotting and Screen-Printing for On-Site Rapid Voltammetric Monitoring of Pb(II) and Cd(II)

“…Several paper-based devices have been reported for heavy metal and metalloid determination by stripping analysis. Most of them involve multi-layered constructions such as: paper disks placed atop planar electrodes [ 36 , 37 , 38 , 39 ]; paper sheets attached on commercial 3-electrode screen-printed electrodes [ 40 , 41 , 42 , 43 ]; paper devices with externally attached electrodes [ 44 , 45 ]. On the contrary, only a handful of truly integrated ePADs have been developed for stripping analysis of heavy metals and metalloids fabricated by: laquer spraying/screen-printing [ 46 ]; wax melting/sputtering [ 47 ]; wax printing/screen-printing [ 48 , 49 ]; inkjet-printing/screen printing [ 50 ].…”

“…On the contrary, only a handful of truly integrated ePADs have been developed for stripping analysis of heavy metals and metalloids fabricated by: laquer spraying/screen-printing [ 46 ]; wax melting/sputtering [ 47 ]; wax printing/screen-printing [ 48 , 49 ]; inkjet-printing/screen printing [ 50 ]. Among all the aforementioned paper-based sensors, only very few deal with simultaneous stripping determination of Pb(II) and Cd(II) [ 36 , 41 , 42 , 43 ] and are all based on modular designs. In this context, it is highly desirable to develop integrated, disposable, low-cost ePADs for the simultaneous determination of Pb(II) and Cd(II) by stripping analysis.…”

Chemiluminescence-Derived Self-Powered Photoelectrochemical Immunoassay for Detecting a Low-Abundance Disease-Related Protein

“…With the fast-growing demand for point-of-care tests (POCTs) and rapid assays, paper-based devices, including microfluidic paper-based analytical devices (μPADs) and paper electrodes (PEs), have gained the attention of researchers due to their manageable cost, ease of manufacture, portability, and maneuverability. − Attracted by the advantages of paper-based applications, many communities are striving to develop innovative and pragmatic test platforms to satisfy the testing concerns in resource-limited and developing countries, including the development of paper-based coupled colorimetric, − (photo)­electrochemical, − chemiluminescent, , and fluorescence testing methods. − …”