Inks in the Analytical Laboratory: A Forensics Activity for Undergraduate Students
Jorge Sáiz,
Javier Rupérez-Pascualena
Abstract:Here, we present a laboratory activity in which the students
work
on an analysis of a questioned document that was written with one
out of five possible pens. As a forensics study, the activity applied
chemistry and analytical chemistry tools to solve the case. The students
were able to apply polarity and solubility concepts to select and
discard some pens. They also learned the basics of fluorescence and
the possibilities of using it to detect falsifications. Then, they
were able to set up the detection condi… Show more
“…9 HPLC has also been used in investigating a range of natural dyes 10−12 and recently, the forensic analysis of inks. 13 Yet, there are only a few examples of HPLC being used in the general chemistry laboratory. 14,15 There are, however, analogous systems, such as RGB image analysis, 16 spectrophotometry, 17,18 and column chromatography 19,20 reported in the general chemistry literature that teach students related concepts.…”
A major
challenge when designing new experiments for the general
chemistry laboratory is introducing students to the necessary techniques
while keeping the experiment engaging and accessible. This work presents
a new multiweek activity designed to introduce students to advanced
instrumentation in the form of high-performance liquid chromatography
(HPLC) via a related scripted thin layer chromatography (TLC) experiment
using dyes from markers and food colors. These dyes have different
polarities so can be separated easily with their visual nature, making
them ideal for laboratories. First, commercial food colors are introduced,
which contain multiple dyes that are quantified using HPLC, and then,
students build upon this in the identification and quantification
of dyes on candy. These laboratories have been implemented at Concordia
College over the last several years with assessment data showing student
gains in the understanding of polarity and chromatography and engagement
with the laboratory activity.
“…9 HPLC has also been used in investigating a range of natural dyes 10−12 and recently, the forensic analysis of inks. 13 Yet, there are only a few examples of HPLC being used in the general chemistry laboratory. 14,15 There are, however, analogous systems, such as RGB image analysis, 16 spectrophotometry, 17,18 and column chromatography 19,20 reported in the general chemistry literature that teach students related concepts.…”
A major
challenge when designing new experiments for the general
chemistry laboratory is introducing students to the necessary techniques
while keeping the experiment engaging and accessible. This work presents
a new multiweek activity designed to introduce students to advanced
instrumentation in the form of high-performance liquid chromatography
(HPLC) via a related scripted thin layer chromatography (TLC) experiment
using dyes from markers and food colors. These dyes have different
polarities so can be separated easily with their visual nature, making
them ideal for laboratories. First, commercial food colors are introduced,
which contain multiple dyes that are quantified using HPLC, and then,
students build upon this in the identification and quantification
of dyes on candy. These laboratories have been implemented at Concordia
College over the last several years with assessment data showing student
gains in the understanding of polarity and chromatography and engagement
with the laboratory activity.
As chemical and material wastes have harmful effects
on both human
and environmental health, waste management is an essential component
of climate action. To educate students about core green chemistry
principles, it is necessary to teach and practice waste management
strategies in the laboratory. Following a previously described laboratory
exercise where students use natural feedstocks to tie-dye fabric,
this follow-up exercise focuses on students upcycling waste dye and
mordant baths into pigment, inks, and paints and evaluating their
chemical and material properties and applications. The exercise has
students generate, handle, store, use, and properly dispose of waste
feedstocks and products while creating biobased art media. It expands
on the first exercise exploring the use of reagents from renewable
resources to create waste-derived versions of historical iron gall
ink formulations. These waste-based art media are then analyzed, distinguishing
optical, textural, and drying properties using the Munsell Color System
and a texture wheel. Students iteratively formulate media to target
applications including writing, printing, and painting. The exercise
connects the practice of waste management and the explores the relationships
between material composition, function, and application. The exercise
both educates students on waste management strategies and reduces
the amount of waste generated during laboratory classes. By circularizing
materials in the teaching laboratory, students and educators foster
an increasingly sustainable and circular economy.
An upper division laboratory experiment focuses on the
characterization
of the chemical structures of fiber samples using a solubility test
and FTIR (Fourier transform infrared) spectroscopy, and solvent extraction
followed by TLC (thin layer chromatography) and UV–vis spectrometry
for the detection of the dye component found in the fiber. Laboratory
reports and embedded questions are used to assess the accomplishment
of the learning outcomes. This activity provides students with additional
opportunities (beyond those presented in introductory classes) to
work with widely applicable techniques and simultaneously links polymer,
organic, and general chemistry concepts with forensic applications.
The protocol can also be easily adapted to address a variety of learning
objectives.
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