Low-cost Screen-printed Electrodes Research Articles

A hydrogel-modified electrochemical biosensor for the rapid detection of ammonia‑nitrogen-resistant bacteria

Ammonia‑nitrogen wastewater is one of the main pollutants in the current environment. Rapid detection of microorganisms resistant to ammonia‑nitrogen provides a basis for bioremediation of ammonia‑nitrogen contaminated sites. This study uses electrochemical analysis for efficiently detecting of ammonia-resistant bacteria, utilizing a commercially available, low-cost screen-printed electrode (SPE) modified with agarose-based hydrogel (gel) or graphene oxide (GO). At the same time, the study employed electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) to monitor bacterial growth, revealing Escherichia coli (E. coli) inhibition upon ammonia‑nitrogen addition, while Raoultella terrigena (RN1) and Pseudomonas (RN2) exhibit tolerance. The method provides sensitivity results in <45 min, which is significantly faster than traditional methods. RN1 and RN2 exhibit promising ammonia‑nitrogen removal rates, reaching up to 81 % and 92 %, respectively. This study aimed to develop an effective electrochemical method for rapidly detecting the sensitivity of microorganisms to ammonia‑nitrogen. The method offers advantages such as high speed, efficiency, and cost-effectiveness, potentially providing valuable microbial resources for mitigating ammonia nitrogen wastewater pollution.

Simple Melatonin Determination Using Disposable and Low-Cost Lab-Made Screen-Printed Carbon Electrode

This work describes the preparation and application of a screen-printed electrode (SPE) for direct melatonin (MT) determination in samples of saliva and urine. The low-cost SPE was obtained using a simple and feasible 2D printing methodology and a lab-made conductive ink based on graphite powder and colorless nail polish. The proposed electrode showed similar electrochemical performance compared to a commercial SPE towards melatonin oxidation. Based on electrooxidation of melatonin recorded at +0.62 V an electroanalytical method was developed using the lab-made SPE under square wave voltammetric conditions. Repeatability and reproducibility studies showed that the relative peak current values did not show significant differences between them. Under optimized parameters inherent to the methodology and voltammetric technique, the proposed SPE presented a linear dynamic range (LDR) between 0.25 to 75.0 μmol L−1 (R2 = 0.99), and calculated limit of detection (LOD) and limit of quantification (LOQ) of 25.8 and 83.3 nmol L−1, respectively, were obtained. The effect of other biologically relevant compounds such as glucose, urea, and estradiol was investigated, and non-significative signal interference was observed. The method proposed was successfully applied to MT determination in spiked samples providing good recovery values between 95.6 to 104%.