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Atmospheric aerosol or particulate matter (PM) has huge potential to affect health and climate. The adverse effects of particulate matter exposure on human health depend on its size and composition, and toxic metals, such as lead, are some of the constituents. Conventional methods to detect lead include atomic absorption and flame emission spectroscopy, which require high cost and bulky instrumentation, generate noticeable amounts of residues and need trained technicians or users. In this study, a simple, portable and low-cost electrochemical method is reported to determine bioavailable lead in PM using an unmodified screen-printed carbon electrode (SPCE) based on square wave anodic stripping voltammetry performed on a portable potentiostat. The proposed approach has provided excellent sensitivity (21 ± 1 μA μg−1L) with a detection limit of 0.023 μg L−1, low interference from other metals and a recovery of ca.90%. The accuracy of the method was confirmed by comparison with inductively coupled plasma mass spectrometry. Moreover, the use of the SPCE exhibited good stability allowing quantification of lead in atmospheric PM collected in Goiania city (2016). The achieved concentrations of lead ranged from 0.04 to 0.21 ng m−3. Based on the reported data, the unmodified SPCE device has successfully demonstrated great selectivity and sensitivity for environmental analysis at trace levels, making possible the monitoring of bioavailable lead in PM samples.

This study describes the use of electrochemical paper-based analytical devices (ePADs) drawn with graphite pencil for the determination of ascorbic acid (AA) in commercial tablets. ePADs were fabricated using vegetal paper and graphite pencil. First, the three-electrode electrochemical cell drawn using a graphical software and toner lines were laser printed on the vegetal paper surface to delimit the electrode areas. Then, the electrode regions were manually painted with graphite pencil. Afterwards, the pseudo-reference electrode was defined with the deposition of silver ink over the graphite surface. Cyclic voltammetry and square wave voltammetry (SWV) experiments were performed to optimize the electroanalytical parameters as well as to quantitatively determine the AA concentration in two commercial tables. ePADs exhibited linear behavior for a concentration range between 0.5 and 3.0 mmol L−1. The achieved limit of detection and sensitivity were 70 μmol L−1and 0.47 μA/mmol L−1, respectively. The AA concentration levels found by SWV experiments in both CenevitTMand Energil CTMwere 2.80 ± 0.02 and 3.10 ± 0.01 mmol L−1, respectively. The accuracy of the proposed devices was investigated through recovery experiments in three concentration levels and it presented values between 95 and 115%.

We describe for the first time the fabrication of a paper-based microchip electrophoresis (pME) device with integrated hand-drawn pencil electrodes to perform capacitively coupled contactless conductivity detection (C4D). This low-cost device (less than $0.10) revealed great capability to dissipate heat, good injection-to-injection repeatability, and ease of attaching pencil-drawn electrodes on the separation channel. The feasibility of the proposed pME-C4D device was successfully demonstrated with the separation of bovine serum albumin and creatinine within 150 s with baseline resolution. The limits of detection values for albumin and creatinine were 20 and 35 μmol L−1, respectively. These biomolecules present clinical relevance as evidence of kidney failure. The proposed pME-C4D offers great potential to be explored in the diagnosis of diabetes mellitus and heart disease.

This study reports the use of microfluidic paper-based analytical devices (μPADs) associated with colorimetric detection for the determination of nitrite in clinical, food and environmental samples. μPADs were fabricated by a simple and fast stamping process in a geometry containing eight circular detection zones and one central zone to sample inlet interconnected by microfluidic channels. The colorimetric determination of nitrite was performed through the modified Griess reaction. Detection zones were spotted with a 0.75 μL aliquot of a solution containing 50 mM sulfanilamide, 1.2 M hydrochloric acid and 4 mM N-(1-naphthyl)ethylenediamine. The monitoring of the background colorimetric response revealed good stability over 12 h for devices stored in the absence of light. After the addition of standard or real samples, the resulting images were captured with a scanner, converted to a color scale and analyzed in the magenta channel. The analytical sensitivity and the limit of detection achieved after a preconcentration stage were 0.56 (AU μM−1) and 5.6 μM, respectively. The preconcentration provided an enrichment factor of ca.3.2 times. The concentration levels of nitrite were successfully determined in saliva, preservative water, ham, sausage and river water samples. The concentration levels attained for each sample using μPADs were compared to the values found by spectrophotometry and there was no significant difference from one another at a confidence level of 95%.