In this study, simple, cheap, fast, and portable microfluidic paper-based analytical devices (Î¼-PADs) were developed and used for chromium (Cr) and copper (Cu) assay in environmental samples. The Î¼-PADs were prepared for the determination of total Cr by adding reagents to the pretreatment and detection zones. The concentrations in soil and lettuce samples collected from old Kombolcha industrial area were determined by the Î¼-PADs and a UV-Vis spectrophotometer. The mean concentrations of total Cr in soil samples were in the range of 737-810 Î¼g g-1 for Î¼-PADs and 726-776 Î¼g g-1 for UV-Vis spectrophotometric analysis, respectively. Similarly, the mean concentrations of total Cr in lettuce samples were in the range of 27-31 and 20-21 Î¼g g-1 for Î¼-PADs and UV-Vis spectrophotometric analysis, respectively. A paired t-test showed that the mean total Cr concentrations determined in the soil and lettuce samples were not significantly different between Î¼-PADs and UV-Vis spectrophotometric analysis at the 5% level of significance. Concentrations of total Cr in all soil samples were above the permissible limit set by European Union Standards (100 Î¼g g-1). Similarly, the concentrations of Cr in all lettuce samples were above the maximum permissible levels set by FAO/WHO standards (2.3 Î¼g g-1). Moreover, evaluating Cr contamination level using the geo-accumulation index indicated that the soils were contaminated with Cr moderately to heavily. The Î¼-PADs demonstrated good detection capability in soil and lettuce samples with higher levels of Cr, but poor sensitivity in water samples. Thereby in the subsequent study, reagent optimization and enrichment approaches were used for the assay of Cr and Cu in water samples, respectively to enhance analytical sensitivity of Î¼-PADs. Speciation of Cr was demonstrated using Î¼-PADs that permit the determination of (Cr(VI)) and (Cr(III)) via online oxidation. The Î¼-PADs consist of left and right channels that allow the simultaneous measurements of Cr(VI) and total Cr based on the colorimetric reaction of Cr(VI) with 1,5-diphenylcarbazide (DPC). For the determination of Cr(VI), a sample solution was directly reacted with DPC in the left channels whereas total Cr was determined in the right channels, which permitted online oxidation in the pretreatment zone containing cerium (IV) (Ce(IV)). Speciation was achieved by measuring the Cr(VI) and total Cr mean color intensity in the left and right channels followed by determination of Cr(III) by subtracting Cr(VI) from total Cr concentration. The limits of detection and quantification were 0.008 and 0.02 mg L-1 for Cr(VI) and 0.08 and 0.1 mg L-1 for Cr(III), respectively. The linear dynamic ranges were 0.02-100 mg L-1 and 0.1-60 mg L-1 for Cr(VI) and Cr(III), respectively. The RSDs were less than 7.5%. The results obtained using Î¼-PADs were in good agreement with those obtained via ICP-OES. Trace analysis of metal ions is problematic in the Î¼-PADs due to their inherent low sensitivity. Thus, the Î¼-PADs were coupled with an enrichment method called coprecipitation approach using aluminum hydroxide for determining the trace level of Cu(II) in water samples. The experimental conditions including pH, centrifugation rate and time, reagent volumes and concentrations were optimized. The enrichment factor was found to be 250. Detection limit as low as 0.003 mg L-1 with 0.01-2 mg L-1 of linear dynamic range were achieved. The relative standard deviations for intra-day and inter-day precision were 3.2 and 4.6%, respectively (n = 9). The results of spiked water samples using Î¼-PADs coupled with coprecipitation and ICP-OES analysis were in a good agreement as paired t-test indicated no significant differences between the results. Thus, the results of the study demonstrated that Î¼-PADs could potentially be utilized for environmental monitoring in developing countries where environmental pollution is rampant and the availability of sophisticated analytical instruments are scarce.