Supercritical Fluid Extraction versus Traditional Solvent Extraction of Caffeine from Tea Leaves: A Laboratory-Based Case Study for an Organic Chemistry Course

Abstract

In this case-based laboratory, an instrument sales person attempts to convince an analysis laboratory of the virtues of supercritical fluid extraction (SFE). The sales person deals directly with the laboratory technicians who will make the decision. Arrangements are made to have SFE instrumentation brought into the laboratory for a comparative study. The extraction and gravimetric determination of caffeine from finely cut tea leaves is chosen as the "test". The technicians are divided into two groups. Group A performs a traditional solvent extraction using methylene chloride (CH 2 Cl 2 )/alkaline water and group B using a SFE method. Students play the role of laboratory technicians and use the data collected to determine which method they would choose considering several variables and issues. It puts the student into a real-world situation and requires them to apply their critical-thinking skills to make a decision. This case-based laboratory exposed second-year science students to a new technology, provided them with an opportunity to compare and contrast competitive methods, and promoted green chemistry initiatives. An unexpected instrument anomaly affected several students in Group B. How this anomaly was reflected in student assessment of this case-based laboratory is also presented.

Determination of Alkali Hydroxide Concentration Based on Green Consideration

“…The contamination of the wastewater produced by chemical laboratory is a worldwide problem. Seeking for efficient methods to reuse laboratory wastewater produced in laboratory teaching and applying the methods in chemistry laboratory courses will help students establish the philosophy of environmental protection and sustainable development [1][2][3][4][5][6][7][8] .…”

“…Different from the previous methods, this paper describes a successful design of the teaching experiment into a green one which does not need to purify the wastewater produced by titration. The teaching reform will help students learn how to design and carry out a green chemical experiment [6][7][8][9] .…”

Extraction of dyes contained in glow sticks using liquid CO2

“…Both liquid CO 2 and supercritical CO 2 can be used as a substitute for volatile organic solvents in extraction and chromatographic methods (1)(2)(3)(4)(5)(6)(7). CO 2 can be obtained from and returned to the air in a cyclic fashion, it is neither toxic nor flammable, and its use as a solvent avoids the production of large quantities of waste solvent (7).…”

Determining the Antifungal Agent Clioquinol by HPLC, the Not So Pure Preparation: A Laboratory-Based Case Study for an Instrumental Analytical Chemistry Course

“…The laboratory-based case study approach is becoming ever more common in science-based courses because of the documented advantages offered, and the need for the implementation of more active learning and critical thinking initiatives at the undergraduate level. ,,, Compared to conventional laboratory experiments, the case study approach provides students with a better appreciation of how scientists actually conduct themselves and solve problems in the “real world”, and challenges student critical thinking skills and creativity in ways “cook book” experiments too often do not. Well-designed laboratory-based case study experiments should to the greatest extent possible involve teamwork, and require students to collect, critically assess, and apply their experimental data to address the question(s) posed in the case.…”