Figure 4
(a) A colorimetric μPAD assay detecting Cr(VI) using diphenylcarbazide (DPC) and H2SO4. (b) In the presence of increasing concentrations of Cr(VI), an increasing magenta color change is produced, as measureable by a change in normalized absorbance (A) of the green band (λmax = 540 nm) reflected light intensity. (c) Dual-target and negative control solutions were assayed and compared with a (d) DPC-Cr(VI) standard curve created by single-target μPAD detection of Cr(VI) concentrations using DPC (n = 3). (e) There was no significant difference in normalized absorbance measured between the dual target control solutions and 2.5 ppm Cr(VI). Conversely, there was a significant difference between 2.5 ppm Cr(VI) and all negative control solutions (p < 0.05).
