PDMS based photonic lab-on-a-chip for the selective optical detection of heavy metal ions

Abstract

The selective absorbance detection of mercury(II) (Hg(2+)) and lead(II) (Pb(2+)) ions using ferrocene-based colorimetric ligands and miniaturized multiple internal reflection (MIR) systems implemented in a low-cost photonic lab on a chip (PhLoC) is reported. The detection principle is based on the formation of selective stable complexes between the heavy metal ion and the corresponding ligand. This interaction modulates the ligand spectrum by giving rise to new absorbance bands or wavelength shifting of the existing ones. A comparative study for the detection of Hg(2+) was carried out with two MIR-based PhLoC systems showing optical path lengths (OPLs) of 0.64 cm and 1.42 cm as well as a standard cuvette (1.00 cm OPL). Acetonitrile solutions containing the corresponding ligand and increasing concentrations of the heavy metal ion were pumped inside the systems and the absorbance in the visible region of the spectra was recorded. The optical behaviour of all the tested systems followed the expected Beer-Lambert law. Thus, the best results were achieved with the one with the longest OPL, which showed a linear behaviour in a concentration range of 1 μM-90 μM Hg(2+), a sensitivity of 5.6 × 10(-3) A.U. μM(-1) and a LOD of 2.59 μM (0.49 ppm), this being 1.7 times lower than that recorded with a standard cuvette, and using a sample/reagent volume around 190 times smaller. This microsystem was also applied for the detection of Pb(2+) and a linear behaviour in a concentration range of 3-100 μM was obtained, and a sensitivity of 9.59 × 10(-4) A.U. μM(-1) and a LOD of 4.19 μM (0.868 ppm) were achieved. Such a simple analytical tool could be implemented in portable instruments for automatic in-field measurements and, considering the minute sample and reagent volume required, would enable the deployment of high throughput environmental analysis of these pollutants and other related hazardous species.

Manipulation and Optical Detection of Colloidal Functional Plasmonic Nanostructures in Microfluidic Systems

“…Transmission spectra of AuNPs at very low concentration can be recorded if the measurement is done collinearly to the microfluidic channel. Ibarlucea et al [57] present a convenient optical setup. The incoming light is injected into a PDMS polymer-based microfluidic system via an optical fiber coupled with a 2D lens fabricated in the polymer.…”

Applications of autonomous microfluidic systems in environmental monitoring

“…The photonic LOC presented by Ibarlucea et al 62 is an alternative to the previously mentioned strategies for the detection of Pb(II) and Hg(II), and is based on selective complexation with ligands derived from ferrocene. The resulting complexes produce new absorbance bands and wavelength shifts.…”

Innovative High-Throughput SAXS Methodologies Based on Photonic Lab-on-a-Chip Sensors: Application to Macromolecular Studies

“…In this regard, the non-invasive on-chip characterization of biological and chemical responses by UV-Vis spectrophotometry has led to numerous PhLoC and optofluidic sensors [19,20]. These systems have been proposed for a wide range of applications, from cell culturing and cell analysis [21,22,23,24] to heavy metal ion detection [25,26], enzymatic catalysis for different applications [27,28], and protein concentration measurements [29]. More particularly, this technology can be of special interest to investigate reactions involving radioactive elements, (e.g., for nucleation studies [30], mass transfer [31], etc.).…”