A novel and quick (sub-minute) method for synthesizing gold nanoparticles (AuNPs) over electrochemical paper-based devices (ePAD) using a CO2 laser is presented. The ePAD, fabricated by laser-scribing carbonization of kraft...

The production of electrically conductive additive manufacturing feedstock from recycled poly(lactic acid) (rPLA), carbon black (CB), and bio-based plasticiser castor oil is reported herein. The filament was used to print...

Levamisole is the most common adulterant found in cocaine samples and its electrochemical determination in cocaine seized samples is a challenge due to peak overlapping with cocaine. Herein, we propose a deconvolution procedure for levamisole determination in seized cocaine samples using screen‐printed carbon electrodes (SPE). Square‐wave voltammetry in 0.04 mol L−1 Britton Robinson buffered solution (pH 8.0) was selected in combination with optimized SWV parameters (f=8 s−1, a=10 mV and ΔEs=1 mV) to result in the best peak resolution to apply the deconvolution procedure. Deconvoluted responses of levamisole in the presence of cocaine were similar to untreated signals of standard levamisole solutions in absence of cocaine. A linear response was obtained in the range of 20–100 μmol L−1 (r=0.995). The results obtained for the analysis of a seized cocaine sample was statistically similar to that obtained by gas chromatography. Other adulterants found in cocaine street samples (paracetamol, glucose, phenacetin, caffeine, boric acid and lidocaine) did not affect the treated of voltammetric responses of levamisole. A pharmaceutical sample containing levamisole was also analyzed on SPEs and a recovery of 93±2 % was obtained (no deconvolution required for this sample), showing great applicability of SPEs for forensic and pharmaceutical analyses.

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The determination of antioxidant capacity of food samples using disposable polyester screen‐printed graphitic macroelectrodes (SPGE) coupled with a batch‐injection cell based on the measurement of the consumption of 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH.) is reported. The SPGEs are organic‐resistant electrodes and thus compatible with food samples and organic solvents used to dissolve DPPH.. A micropipette controlled the release (193 μL s−1) of sample (150 μL) upon the sensor/working electrode immersed in electrolyte (1 : 1 ethanol/methanol containing 0.05 mol L−1 LiCl). The first demonstration of this protocol was devoted to the analysis of edible oils. The remaining DPPH. was amperometrically detected at +0.1 V (vs. pseudo AgCl). The antioxidant capacity (percentage of DPPH. scavenging and mg equivalent of tocopherol) was obtained using the proposed and spectrophotometric methods. The results were in agreement according to t‐test (confidence level of 95 %). The method is precise (RSD=2.3 %, n=12), fast (180 h−1), presents low detection limit of DPPH. (1 μmol L−1), and allows on‐site analysis. Moreover, the proposed method can be extended to the analysis of antioxidant capacity of other samples of agricultural and food interests.

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Much effort was made in the literature to put pencil-drawing as an attractive way to fabricate electrochemical sensors. The pencil drawing is one of the easiest, cost-effective, unique single-step methods for fabricating paper-based devices without necessitating any expensive instrumentation by merely transferring the carbon by exfoliation abrasion on paper. Additionally, much has to be done to improve the quality of this transfer carbon to achieve a suitable sensing platform for electrochemical measurements. Hence, this review article aims to bring the new approaches developed in the last five years to circumvent some fabrication problems and enhance this “carbonization” step for electrochemistry detection using paper-based sensors. We will start the discussion on the carbon materials moving to the substrate and finally discuss the strategies to produce the conductive tracks and enhance their properties for sensing applications.