Abstract:

Herein, a workshop focused on the introduction of undergraduate students of analytical chemistry in the current meaning of qualitative analysis is proposed, namely through the binary answer (yes/no) procedures and their validation. In general, analytical chemistry plays a paramount role in our society for making important decisions in many areas, such as food and drugs production, environmental monitoring, medical diagnostics, or forensic investigations. In fact, nowadays there is an increased interest to obtain rapid and simple analytical information to make grounded decisions. In this sense, the demand for qualitative analysis used as a screening tool is high, as it enables saving both time and costs of analysis.

At present, this approach to qualitative analytical chemistry should be an important part of undergraduate education in chemistry to enhance the capacities of students to deal with real issues and for making decisions in a wide variety of scientific fields. To that end, an active learning-based workshop through the application of different presumptive tests commonly used for qualitative analysis of blood in a crime scene is proposed in this work, e.g., Kastle-Meyer phenolphthalein test, leucomalachite green test, and luminol test. This activity is aimed at understanding the functioning and validation of these qualitative tests to examine a hypothetical case: “Maria’s best friend did not show up to their appointment. Concerned about it, Maria went to her friend’s house. Once there, she realized that something had happened to her friend. The house was completely messy and there were suspicious blood stains. Immediately, she called the police to initiate an investigation.” A simulated crime scene and a question about it were the starting point of the proposed activity: is it blood?

This topic was proposed to promote the interest of the students. Considering the increased use of streaming platforms in the last years, many students watch thrillers (series or films) whose plot usually includes certain contents of forensic chemistry that can be used to raise students’ interest in learning about qualitative analysis.

The workshop was divided in three sessions (3 h). Firstly, an introductory session (1 h) was performed by the teacher for explaining basic information about the selected presumptive tests, validation, and the presentation of the practical activity. Then, students were divided into three groups (3 or 4 students per group). Each group was assigned to widen the information about one presumptive test and develop a protocol to resolve the proposed case (two sessions, 2 h). Students have addressed different questions: How suspected samples to be blood should be collected? How qualitative analysis would be performed? What information would be obtained? Is that information reliable for making a conclusion?

The main aim of searching a reasoned answer for the questions is the stimulation of their curiosity promoting the development of deeper interest about qualitative analysis and validation. At the end of this activity, the students obtain the corresponding reasoned information to be able to answer the question. They analyse, summarize, and present the obtained information considering the fundamentals and validation parameters. This activity helps increasing students’ abilities to reach and present grounded decisions. Additionally, the students can improve their confidence and performance in further courses.

Keywords:

Workshop, qualitative analytical chemistry, presumptive tests, Kastle-Meyer test, leucomalachite green test, luminol test, qualitative validation.