RESUMO
Described is the creation, deployment, and evaluation of a video produced about the synthesis and applications of metal-organic frameworks (MOFs). The goal of this project was to gauge the impact of viewing the video on high school students' conceptions of authentic chemistry practices and applications. Additionally, comparisons were made between the use of the video and more traditional face-to-face presentations given by professional scientists. Observations, student surveys, and an interview with the high school chemistry teacher demonstrated the utility of such a video. Specifically, the students who viewed the video reported learning more about the nature of laboratory work in chemistry than other students who did not view the video. Students, regardless of whether they viewed the video or just received a presentation, reported growth in understandings of the applications of chemistry research and porous nanomaterial. Other research chemists are encouraged to consider ways that they could document on video the research that they are performing in order to introduce an untapped audience (high school students) to authentic chemistry research in a practically simple manner. During times of crisis, such as a pandemic, online videos could be a useful tool for high school chemistry teachers to use in collaboration with research faculty, particularly when schools are closed.
RESUMO
In this study, we introduce a modulation strategy for comprehensive two-dimensional gas chromatography (GC×GC) by using a simple and consumable-free modulator. This "Do-It-Yourself" interface comprised a 1.0m×0.25mm segment of MTX-5 metallic column and a low-cost DC power supply. Thermal desorption modulation (TDM) was attained using a dual-stage heater-based modulator in a novel segmented-loop configuration. TDM was achieved by alternating analyte trapping and thermal desorption. Former process relied on analyte partition to sorbent phase, while latter explored direct resistive heating. Introduction of an intermediate delay segment between the two stages mitigated analyte breakthrough, improving peak symmetry and chromatographic efficiency. This feature was critical to acquire reliable GC×GC modulation using such simple heater-based device. The effects of important modulation variables on 2D separations were investigated, including TDM stage length, dimension of delay loop, and outlet pressure. Significant advances and limitations of proposed TDM strategy were carefully determined. Proposed GC×GC prototype by using an in-oven TDM modulator was successfully applied to a series of challenging matrices, including petroleum distillates, biodiesel, and essential oil. This open-hardware, cost-effective modulator was easy to install and operate, as it circumvented the need for sophisticated components (e.g. moving parts and cooling systems). Therefore, our modulator is a compelling alternative to existing GC×GC solutions to operate in resource-limited laboratories.