Dispersive liquid-liquid microextraction coupled with microfluidic paper-based analytical device for the determination of organophosphate and carbamate pesticides in the water sample.

A microfluidic paper-based analytical device (µ-PAD) is a promising new technology platform for the development of extremely low-cost sensing devices. However, it has low sensitivity that might not enable to measure maximum allowable concentration of various pollutants in the environment. In this study, a dispersive liquid-liquid microextraction (DLLME) was developed as a preconcentration method to enhance the sensitivity of the µ-PAD for trace analysis of selected pesticides. Four critical parameters (volume of n-hexane and acetone, extraction time, NaCl amount) that affect the efficiency of DLLME have been optimized using response surface methodology. An acceptable mean recovery of 79-97% and 83-93% was observed at 1 µg L-1 and 5 µg L-1 fortification level, respectively, with very good repeatability (2.2-6.01% RSD) and reproducibility (5.60-10.41% RSD). Very high enrichment factors ranging from 317 to 1471 were obtained. The limits of detection for the studied analytes were in the range of 0.18-0.41 µg L-1 which is much lower than the WHO limits of 5-50 µg L-1 for similar category of analytes. Therefore, by coupling DLLME with µ-PAD, a sensitivity that allows to detect environmental threat and also that surpassed most of the previous reports have been achieved in this study. This implies that the preconcentration step has a paramount contribution to address the sensitivity problem associated with µ-PAD.

Microfluidic Paper Based Analytical Devices for the Detection of Carbamate Pesticides.

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.