Ahmed Hussen

In the present study, a sensitive microfluidic paper-based analytical device (μ-PADs) integrated with adsorption enrichment procedure was developed to analyze Cr(VI) in water samples. The affecting factors, including pH and amounts of reagents were optimized. The limit of detection of 0.0015 mg L⁻¹ and linear range of 0.005–2 mg L⁻¹ were achieved with good intra- and inter-day precision of 5.1 and 7.6% RSD, respectively. The results obtained by the proposed method were validated by inductively coupled plasma-optical emission spectrometry (ICP-OES). The recoveries of the present method and ICP-OES were ranged from 96.3 to 109.0‬% and 106.0 to 109.7%, respectively. The two sets of (μ-PADs and ICP-OES) results were in a good agreement as paired t-test indicated no significant differences. The proposed method could be utilized for analyzing trace levels of Cr(VI) in water samples in the absence of conventional analytical instruments. Graphical abstract

Microalgae have the ability to utilize nutrients present in wastewater and generate biomass that is abundant in carbohydrates, lipids, and proteins. The ability of microalgae to integrate wastewater management and biofuel production makes them a promising solution for enhancing environmental sustainability. The objective of this study was to assess the potential of local microalgae, Scenedesmus sp., to simultaneously remediate wastewater and produce lipids. The microalgae were cultivated in anaerobically digested brewery effluent, both sterilized and non-sterilized, to evaluate their phycoremediation and lipid production capabilities. The phycoremediation study was investigated by measuring chemical oxygen demand (COD), total nitrogen (TN), ammonium–nitrogen (NH₄⁺-N), and total phosphorus (TP) removal from brewery effluent. Lipids were extracted from microalgal biomass without and with pretreatment methods, such as microwave, autoclave, osmotic stress, oven heating, and HCl digestion in a water bath, to enhance lipid extraction. Results indicate that Scenedesmus sp. achieves higher biomass production in non-sterilized brewery effluent compared to sterilized brewery effluent. Conversely, it attains higher lipid accumulation in sterilized brewery effluent compared to non-sterilized brewery effluent. Scenedesmus sp. also attained a higher removal of TP (69.32%) and COD (77.78%) in non-sterilized effluent, but TN (96.14%) in sterilized brewery effluent. The removal of NH₄⁺-N was nearly 100% in both effluents. The maximum lipid content obtained was 14.79%, which was enhanced by 39.06%, 23.89%, 15.81%, 11.61%, and 4.78% after microwave, HCl digestion, autoclave, osmotic, and oven heating pretreatments, respectively. The findings of this study demonstrate that local microalgae have a great potential for wastewater remediation with lipid production using appropriate pretreatment methods.

A simple, fast, low-cost and sensitive microfluidic paper-based analytical device (u-PADs) integrated with the co-precipitation enrichment procedure was developed to analyse Ni(II) in tap and mineral water samples. The impacting factors, including pH, centrifugation (5 min at 4000 rpm), and amounts of reagents were optimized. The limit of detection of 0.009 mg L-1 and linear range of 0.03-2.00 mg L-1 were achieved with good intra- and inter-day precision (4.7 and 5.6% RSD, respectively). The recovery tests were conducted by spiking tap and mineral water samples and analyzed using the u-PADs after co-precipitation enrichment. The results obtained by the proposed method were validated by inductively coupled plasma-optical emission spectrometry (ICP-OES). The recoveries of the present method and ICP-OES were ranged from 92.4-106.8% and 92.9-97.2%, respectively. The two sets of (u-PADs and ICP-OES) results were in good agreement, as a paired t-test indicated no significant differences. The proposed method could be utilized for analyzing trace levels of Ni(II) in water samples in developing countries where the availability of conventional analytical instruments are significant problems.

The aim of this study is to employ a response surface methodology (RSM) to optimize experimental parameters in microfluidic paper-based analytical devices (µ-PADs). The independent parameters include concentrations and volumes of acetylcholinesterase, acetylthiocholine iodide, and 5,5-dithiobis-(2-nitrobenzoic acid). Their effect on mean color intensity was tested and optimized. From the analysis of variance, high regression and fitting values were obtained between the experimental and RSM predicted mean color intensity. Under optimum conditions, satisfactory linearity (R² > 0.9990) in the range of 0.25–16 mg/L was obtained for the studied pesticides. The limit of detection (LOD) varies from 0.13 to 0.27 mg/L; high precision (RSD of 3.8–8.0%), reproducibility (RSD of 7.2–11.0%), and recovery (78–97%) were achieved. The RSM approach has been demonstrated to be more efficient than the traditional approach. It resulted in a µ-PAD system with less amount of reagent usage and better LOD compared with a univariate approach.

A microfluidic paper-based analytical device (µ-PAD) is a promising new technology platform for the development of extremely low-cost sensing devices.

Microfluidic paper-based analytical devices (μ-PADs) are a new technology platform for the development of extremely low-cost sensing applications. In this study, μ-PADs has been developed for quantitative determination of carbamate pesticides. Key experimental parameters including concentration and volume of acetylcholinesterase, acetylthiocholine iodide and 5,5′-dithiobis-(2-nitrobenzoic acid), incubation time and image capturing time were systematically optimized. Under optimal conditions, the method showed wide range of linearity (0.25–16 mg/L), repeatability (4%–5% RSD) and intermediate precision (7%–10% RSD). Limit of detection was observed to be 0.4, 0.24 and 0.46 mg/L for carbaryl, carbosulfan and furathiocarb, respectively. An acceptable mean recovery (87% to 94%) was observed for the three pesticides at 1 mg/L fortification level. The results reveal that the developed method requires minimal reagents, simple and is easy to handle. It can be used for the quantification of carbamate pesticides in resource limited laboratories without the need for the conventional analytical instruments.