Batch-injection analysis (BIA) has proved to be a suitable technique for many analytical applications. It consists of sample injection from a micropipette tip directly onto the detector surface, immersed in a large-volume cell containing the blank solution, under controlled dispersion conditions. Although the BIA system eliminated the flow manifold used in its precursor flow-injection analysis (FIA), such as tubes, valves, and pumps, it still consumes large reagent volumes, thus leading to more waste generation. In this context, microfluidic paper-based analytical devices (μPADs) can be used as a simple and disposable alternative to conventional FIA and BIA apparatus based on the capillarity properties to disperse the injected solution over the detection system. Electrochemical sensing is a good match for μPADs as conductive materials can be easily integrated into the paper matrix to create electrodes, resulting in low-cost devices for on-site measurements. Paper was already evaluated coupled to FIA, but no reports were found so far coupled to BIA. Hence, we propose the first BIA cell coupled to a μPAD with pencil-drawn electrodes using a laser pre-treated chromatographic paper as the substrate. Spectroscopic and electrochemical techniques showed that the CO2 laser pretreatment of the paper enhanced the electrochemical response for ferricyanide redox probe and paracetamol (PAR). The proposed BIA-μPAD was evaluated by amperometry using pharmaceutical PAR samples as a proof-of-concept, being obtained good linearity (R=0.9961) and recovery values of 97 and 106%. Repeatability (n=16) and reproducibility (n=9) tests also presented good relative standard deviation (RSD) results of 5.1 % and 6.6 %, respectively, and a 76 h-1 analytical frequency, in agreement with conventional BIA apparatus. Limits of detection and quantification were estimated at 0.046 and 0.154 mmol L-1, respectively, attesting the applicability of the proposed device and opening new possibilities related to paper-based devices coupled with flow techniques.

Batch-injection analysis with electrochemical detection coupled with microfluidic paper-based analytical devices: A new approach to conventional BIA apparatus

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