Couple batch-injection analysis and microfluidic paper-based analytical device: A simple and disposable alternative to conventional BIA apparatus

Abstract

Under controlled dispersion conditions, sample injection towards a detector opened essential fields for the Analytical Chemistry fast development methods. Flow injection analysis (FIA) and batch injection analysis (BIA) systems are crucial for injecting the sample in these analytical methods. The BIA system eliminated the flow manifold, with samples injected directly onto the detector inside the batch injection cell. Paper was slightly evaluated coupled to FIA, and no reports were found associated with BIA. Still, it can potentially reduce the BIA manifold by removing the batch injection cell based on the capillarity properties to disperse the injected solution over the detection system. Hence, this article reported the first work coupling batch-injection analysis and microfluidic paper-based analytical device (BIA-μPAD) with pencil-drawn electrodes directly attached to the paper using a CO₂ laser pre-treated chromatographic paper. The laser pretreatment of the paper (optimized conditions: 6.5% laser power, 12 mm s^-1 scan rate, and 12 mm output distance) was essential to enhance the electrochemical response for ferri/ferrocyanide redox couple and paracetamol (PAR), as shown by spectroscopic and electrochemical techniques. The proposed BIA-μPAD was evaluated using pharmaceutical paracetamol samples as proof-of-concept (optimized conditions: 15 μL injected volume and 6.4 μL s^-1 dispensing rate), obtaining good linearity (R = 0.9961) and recovery values ranging from 95 to 103%. Repeatability (n = 16) and reproducibility (n = 9) tests with 1 mmol L^-1 PAR also presented well relative standard deviation (RSD) results of 5.1% and 6.6%, respectively. A sampling frequency of 76 h^-1 was obtained, which is a similar value compared with conventional BIA apparatus. Limits of detection and quantification were estimated in 0.046 and 0.154 mmol L^-1, respectively. Additionally, an improvement in the current response and the sample throughput was observed when comparing FIA and BIA-μPADs, attesting the applicability of the proposed device and opening for new possibilities related to paper-based devices coupled with flow techniques.

Keywords: Batch injection analysis; CO(2) laser pretreatment; Carbon electrodes; Electrochemical detection; Paper-based devices; Paracetamol; Pencil-drawing.