Thin-layer voltammetry of soluble species on screen-printed electrodes: proof of concept

Thin-layer diffusion conditions were accomplished on screen-printed electrodes by placing a controlled-weight onto the cast solution and allowing for its natural spreading.</p

Picturing the thermodynamic universe with Frida Kahlo

Abstract Bringing arts to the science classes remains as a challenging idea. The illustration of a concept with an original painting would bring unexpected advantages. Here we present the use of a painting of Frida Kahlo to illustrate the concept of the thermodynamic universe the surroundings. Such concept is not deeply treated in most textbooks, and it is essential now of analysis of a thermodynamic system. Because of the use of this visual aid, our students were able to distinguish several possible thermodynamic universes, depending on the objective of their study, gaining a more insightful approach than that usually obtained with classical pictographic representations in physical chemistry textbooks.</jats:p

A Direct, Competitive Enzyme-Linked Immunosorbent Assay (ELISA) as a Quantitative Technique for Small Molecules

ELISA (enzyme-linked immunosorbent assay) is a widely used technique with applications in disease diagnosis, detection of contaminated foods, and screening for drugs of abuse or environmental contaminants. However, published protocols with a focus on quantitative detection of small molecules designed for teaching laboratories are limited. A competitive, direct ELISA used to detect and quantify levels of digoxin, a cardiac glycoside, is described. Unique features of this lab include collecting data in quadruplicate followed by statistical analysis of replicates using a Q-test. Use of a microplate reader for measuring absorbances makes data collection extremely quick. Students plot their average absorbance versus log concentration digoxin and fit data to a third- or fourth-order polynomial. They also examine the maximum and minimum absorbance for the assay, determine the region of linearity, and then fit the linear region to a straight-line equation that can be used to determine the concentration of an unknown. The experiment can be completed in a 3-h period and is suitable for upper-level biochemistry, chemistry, and biology students. Although students find understanding a competitive ELISA more challenging than some other experiments, they enjoy learning about this commonly used laboratory technique

Proof of concept for a passive sampler for monitoring of gaseous elemental mercury in artisanal gold mining

Abstract Mercury emissions from artisanal gold mining operations occurring in roughly 80 developing countries are a major workplace health hazard for millions of people as well as the largest contributor to global mercury pollution. There are no portable, cheap, and rapid methods able to inform workers or health practitioners of mercury exposure on site in remote locations. In this work, a proof of concept for a miniaturized mercury sampler, prepared by the direct reduction of gold into the porous nanostructures of Vycor glass (PVG), is introduced. Mercury retention on the PVG/Au sampler induces significant color changes, due to the formation of Au-Hg amalgam that affects the surface plasmon resonance characteristics of the material. The color change can potentially be quantified by the analysis of pictures obtained with a cell phone camera rapidly and onsite. Laboratory experiments showed the viability of using PVG/Au as passive sampler for monitoring of Hg°. PVG/Au samplers were then deployed in an artisanal and small-scale gold mining (ASGM) operations in Burkina Faso and it was able to indicate personal mercury exposures. The amount of mercury quantified in the samplers for all miners was higher than the current personal exposure limit set by the US Occupational Safety & Health Administration (OSHA)