Approach for Downscaling of Electromembrane Extraction as a Lab on-a-Chip Device Followed by Sensitive Red-Green-Blue Detection

A design of electromembrane extraction (EME) as a lab on-a-chip device was proposed for the extraction and determination of phenazopyridine as the model analyte. The extraction procedure was accomplished by coupling EME and packing a sorbent. The analyte was extracted under the applied electrical field across a membrane sheet impregnated by nitrophenyl octylether (NPOE) into an acceptor phase. It was followed by the absorption of the analyte on strong cation exchanger as a sorbent. The designed chip contained separate spiral channels for donor and acceptor phases featuring embedded platinum electrodes to enhance extraction efficiency. The selected donor and acceptor phases were 0 mM HCl and 100 mM HCl, respectively. The on-chip electromembrane extraction was carried out under the voltage level of 70 V for 50 min. The analysis was carried out by two modes of a simple red-green-blue (RGB) image analysis tool and a conventional HPLC-UV system. After the absorption of the analyte on the solid phase, its color changed and a digital picture of the sorbent was taken for the RGB analysis. The effective parameters on the performance of the chip device, comprising the EME and solid phase microextraction steps, were distinguished and optimized. The accumulation of the analyte on the solid phase showed excellent sensitivity and a limit of detection (LOD) lower than 1.0 μg L^–1 achieved by an image analysis using a smartphone. This device also offered acceptable intra- and interassay RSD% (<10%). The calibration curves were linear within the range of 10–1000 μg L^–1 and 30–1000 μg L^–1 (<i>r</i>² > 0.9969) for HPLC-UV and RGB analysis, respectively. To investigate the applicability of the method in complicated matrixes, urine samples of patients being treated with phenazopyridine were analyzed