A simple and rapid approach for on-site analysis of nicotine in tobacco based on a screen-printed electrode as an electrochemical sensor.

In this study, we report a portable kit consisting of a portable workstation, gold screen-printed electrode (SPE), 0.45 µm filter membrane, phosphate buffer solution (PBS), and acetic acid (1%) for point-of-use (POU) analysis of nicotine in tobacco. The activated-screen-printed electrode (A-SPE) displayed superior electron transmission efficiency, and the A-SPE without modification was employed for high-performance analysis of nicotine in actual tobacco after simple sample pretreatment. Remarkably, the fabricated nicotine sensor exhibited a broad working range of 10-100 µg g-1, a low limit of detection (LOD) of 6.4 µg mL-1, good stability, selectivity, and practicality under the optimal conditions. The method was applied to the determination of nicotine in (spiked) samples. Satisfactory recovery results demonstrated that the as-prepared portable kit method with outstanding electrocatalysis ability was feasible for analysis of nicotine in tobacco. Moreover, the values obtained using the A-SPE were in good agreement with those determined by gas chromatography-flame ionization detection (GC-FID), which confirms the feasibility and validity of the present method. The results of the as-proposed portable kit provided a new strategy for analyzing nicotine in actual tobacco samples.

Ultrasensitive monitoring of DNA damage associated with free radicals exposure using dynamic carbon nanotubes bridged interdigitated electrode array.

There are currently increasingly concerns over DNA damage related to free radicals due to their vital roles in human health, especially high-performance detection method. Herein, we report an ultra- sensitive monitoring of DNA damage associated with free radicals exposure using interdigitated electrode (IDE) array for the first time. The proposed IDE array was equipped with DNA-wrapped carbon nanotube-based bridges, which utilized the DNA damage mechanism due to the free radicals' attack and the efficient electrical detection nature of the interdigitated electrode. Experiments have been performed, and the results showed the device's capability for detecting DNA damage induced by multiple free radicals generated from different sources, including the Fenton reaction, UV radiation and cigarette smoke, showing the promising ability for DNA damage detection. In addition, the carbon nanotubes bridge-based interdigitated electrode sensor enabled different levels of sensing of DNA damage with great sensitivity and a wide detection range. It was illustrated that the ultrasensitive detection of free radicals generated from ultraviolet radiation (15 min - 125 min), cigarette smoke tar (1 µg/mL to 10 µg/mL) and Fenton reaction under different concentration of H2O2 (2.5 pM - 100 pM), have been detected successfully. Typically, the IDE array supports further performance improvement for the electrochemical detection in an ultrasensitive and high throughput route.

A facile approach for rapid on-site screening of nicotine in natural tobacco.

Nicotine (Nic) exposed to the environment which comes from tobacco products is the main addictive agent and specific classes of hazardous compound that merit concern. In this study, we have established a fast and reliable method to achieve specific detection of Nic in natural nicotiana tabacum within 30 s through a miniaturized platform based on screen printed gold electrode (SPE). A simple electrochemical pretreatment mean was employed on gold surface that led to the exposure of Au (111) facet and a convenient sample pretreatment method was adopted to realize the extraction of Nic in tobacco. The present electrochemical sensor exhibits an ample range of sensing from 10 µg/g to 200 µg/g, which is able to compliance with tobacco industry testing standards of actual samples. Over 60 sampling points from different origins in China or other countries were performed with direct analysis using this method and satisfactory results have been obtained. The proposed approach was demonstrated to be a very promising platform for significantly improving analytical efficiency in laboratories as well as for monitoring the source reduction control of Nic in the environment.

N-Carbamoylmaleimide-treated carbon dots: stabilizing the electrochemical intermediate and extending it for the ultrasensitive detection of organophosphate pesticides.

To date, numerous methods have been reported for the detection of organophosphorus pesticides (OP) due to their severe potential hazard to the environment, public health and national security. However, very few works have ever found that the signal loss of thiocholine (TCh) during electrochemical processing is a key factor leading to the low sensitivity of acetylcholinesterase (AChE)-based OP electrochemical sensing platforms. Herein, we propose an ultrasensitive detection method for multiple OPs including parathion-methyl, paraoxon, dimethoate and O,O-dimethyl-O-2,2-dichlorovinyl-phosphate using N-carbamoylmaleimide-functionalized carbon dots (N-MAL-CDs) as a nano-stabilizer. For the first time, Michael addition is introduced into an AChE-based OP electrochemical sensing platform to enrich the electrochemical intermediate TCh. The Michael addition between TCh and N-MAL-CDs is demonstrated via XRD, FTIR, SEM and EDS elemental mapping experiments. Due to the stabilization and enhancement of TCh with N-MAL-CDs, the as prepared OP sensing platform achieves ultrahigh sensitivity by detecting the initial electrochemical signals of TCh without signal loss, showing a wide linear range of 3.8 × 10-15-3.8 × 10-10 M for parathion-methyl and 1.8 × 10-14-3.6 × 10-10 M for paraoxon, with a limit of detection of 1.4 × 10-15 M for parathion-methyl and 4.8 × 10-15 M for paraoxon.