Identification of Tree Species by Their Defense Compounds: A Study
with Leaf Buds of White and Silver Birches
Marianna Manninen,* Veli-Matti Vesterinen, Anna-Kaisa Vainio, Heidi Korhonen, Maarit Karonen,
and Juha-Pekka Salminen
Cite This: J. Chem. Educ. 2021, 98, 973−981 Read Online
ACCESS Metrics & More Article Recommendations *sı Supporting Information
ABSTRACT: Plants encounter several different threats that affect
their well-being during the spring. With chemistry, plants may defend
themselves from, for example, excess UV-radiation and herbivores. The
defense compounds between plant species vary, which makes it
possible to utilize chemistry in identifying the plant species. In this
laboratory experiment, students extracted the defense compounds from
the surface of leaf buds, estimated the total phenolic content of the
extract, and determined its antioxidant activity. In addition, the
chemical fingerprints of the leaf buds were analyzed by liquid
chromatography combined to mass spectrometry to identify the
species as white birch, silver birch, or some other tree species. The
laboratory experiment was performed with secondary school and
university students in one approximately 3 h laboratory session. Pre-
and post-tests done by the university students showed that the experiment provided students a basic understanding of how the
instruments function and what they are used for. Their mind maps of the chemistry of plants were concentrated on the primary
metabolites, but the experiment widened their views of specialized metabolites and their functions in plants, thus encouraging the
students to combine chemical and biological information.
KEYWORDS: Analytical Chemistry, Hands-On Learning/Manipulatives, High School/Introductory Chemistry,
Interdisciplinary/Multidisciplinary, Mass Spectrometry, Natural Products, Plant Chemistry, UV−Vis Spectroscopy
■ INTRODUCTION
White birch and silver birch can be hard to separate from one
another during the winter and spring time. However, chemistry
can reveal the difference easily. In fact, the epicuticular leaf
surface flavonoids have successfully been utilized before in
distinguishing Betula pendula and Betula pubescens type birch
species.1 Flavonoids are found on the leaf surface of various
plants,2−6 and they function as an important part of the
chemical defense of plants by protecting plants from excess
solar radiation7 and herbivores,8−10 and act as antioxidants.11
In addition to flavonoids, other compounds such as
terpenoids12 and coumarins13 are involved in the chemical
defense of plants. Looking into the chemistry of leaf buds offers
therefore an interdisciplinary opportunity to learn about the
biology of the plant as well.
Interdisciplinary approaches have been widely utilized in
chemistry education. Previous publications have described
laboratory experiments and activities in the context of, for
example, forensic science,14 herbicides,15 cell and molecular
biology,16 archeology,17 and music.18 Even entire courses have
been created around an interdisciplinary theme, such as beer
brewing,19,20 pigments,21 and plants.22 Interdisciplinary teach-
ing may help in engaging students, increasing meaningful
learning, and connecting chemistry to real-world prob-
lems.16,19,21,23 Heinrich et al. describe how an interdisciplinary
approach may also promote the “authentic big picture” of
scientific research to students.23 This laboratory experiment
shares the same goal by giving an example of an
interdisciplinary research problem.
In addition to the interdisciplinary topic, authenticity of the
laboratory experiment described here is supported by utilizing
modern methods and instruments. Use of authentic practices
has been seen to contribute to perceived relevance and to
evoke interest, as long as students are sufficiently familiar with
the chemical concepts and methods involved.24 As instrumen-
tation plays a huge role in chemical research and practice, there
is a need to familiarize students with the use and role of
modern research methods and instruments on all levels of
education.25,26 Hands-on exposure to the state-of-the-art
Received: June 8, 2020
Revised: December 15, 2020
Published: January 15, 2021
Laboratory Experimentpubs.acs.org/jchemeduc
© 2021 American Chemical Society and
Division of Chemical Education, Inc.
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J. Chem. Educ. 2021, 98, 973−981
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research instrumentation is seen especially valuable for
university chemistry education.27
Analytical techniques combining liquid chromatography
(LC) to mass spectrometry (MS) are routinely used in
chemistry research, and numerous laboratory experiments
utilizing LC-MS have been published in this Journal.28−36
However, only a small number of them provide a context that
students would be familiar with from everyday life. In order to
introduce this modern technique to students, a familiar context
could make the abstract theory more interesting and worth
understanding.34 Even smaller number of the experiments have
been designed for an audience outside of university.36 Yet, they
would benefit the most from having a glance into the world of
chemistry research by trying out the instruments used by
scientists, since students outside university do not usually have
a possibility to use modern methods and instruments.
Here we describe a laboratory experiment where students
extract the epicuticular compounds of leaf buds, identify the
birch species by ultrahigh performance liquid chromatography
combined with mass spectrometry (UHPLC-MS), and
determine the antioxidant activity (AOA) and total phenolic
content (TPC) of the leaf bud extract. It can be completed in
one less than 3 h laboratory session and is suitable for
secondary school students and introductory chemistry courses
in university. The main goals for the experiment are (I) to
demonstrate the chemical differences between plants and thus
make the students combine chemical and biological knowl-
edge, and (II) to introduce students to modern analytical
methods, that is, spectrophotometry and especially LC-MS.
Students’ understanding of the chemistry of plants was tested
with mind maps that the students created at the beginning of
the laboratory session, and which they could supplement at the
end of the laboratory session. Pre- and post-tests were used to
assess how well students understood the methods before and
after the laboratory work.
■ EXPERIMENTAL OVERVIEW
Laboratory Procedure
The experiment was tested with university students as well as
secondary school students. The university students used
freeze-dried leaf bud samples chosen for them beforehand.
The secondary school students collected their samples by
themselves and stored the samples in a fridge (4 °C). The leaf
buds were extracted by dropping one leaf bud into an
Eppendorf tube containing 2 mL of ethanol−water (95/5, v/v)
for 30 s. After that, the extract was filtered with a syringe and
0.20 μm PTFE filter into a new Eppendorf tube. A volume of
500 μL of the extract was pipetted into a glass vial for the LC-
MS analysis. The total phenolic content was estimated with the
modified Folin−Ciocalteu assay,37 where 150 μL of the plant
extract was pipetted into a tube containing 1 mL of the Folin−
Ciocalteu reagent. After mixing gently, 2 mL of 20% Na2CO3
(m/v) solution was added to the tube. The color of the
solution was recorded by comparing the color to a color chart
after 20 min (Figure 1A). A modification of the DPPH assay38
was used to determine the antioxidant activity of the extract. A
volume of 450 μL of the plant extract was pipetted into a tube
containing 3 mL of DPPH solution, and the color was
compared to a color chart after 15 min (Figure 1B).
The TPC was measured at 730 nm with a spectropho-
tometer, and the result was presented as milligrams per liter
using a preinstalled calibration curve with gallic acid as the
standard. The AOA was measured at 517 nm, and the students
calculated the AOA from the absorbance reading with the
calibration curve (gallic acid as the standard) that was given in
the instructions. The LC-MS analysis was carried out at the
same time with the Folin−Ciocalteu and DPPH assays, and the
instrument was operated by the instructor. The instrument
used in the experiment was an Acquity UPLC system (Waters
Corp., Milford, MA, USA) coupled with a Xevo TQ triple-
quadrupole mass spectrometer (Waters Corp.). Gradient
elution and selected ion recording (SIR) were utilized in the
novel method that had 3.5 min analysis time per sample. The
LC-MS parameters and other details for the instructor are
given in the Supporting Information.
Participants and Setting
This study was conducted in spring 2019 and 2020 with 125
students: 13 lower secondary school students (age 14−15
years), 59 upper secondary school students (age 15−18 years),
and 53 university students of a first-year laboratory course on
experiments in general chemistry. The students performed the
experiment in one approximately 3 h session. Each university
student analyzed one sample and measured the TPC and AOA
spectrophotometrically. In the other groups, the number of
samples that the students analyzed varied, and some groups
evaluated the TPC and/or AOA only visually. Details of the
different student groups are given in the Supporting
Information.
Feedback was collected from all student groups. To evaluate
the learning outcomes of this laboratory experiment, the
university students had several pre- and post-tasks. Two weeks
before the laboratory exercise, they answered to a pretest
measuring their knowledge of the chemical research instru-
ments. The students were given 15 min time to answer the
following four questions:
• Describe how a spectrophotometer works.
• Describe how a liquid chromatograph works.
Figure 1. Examples of the range of colors observed in (A) the Folin−Ciocalteu assay for the total phenolic content and (B) the DPPH assay for the
antioxidant activity.
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• Explain what an ion source is.
• Describe how a mass spectrometer works.
One week before the experiment, the university students
received the instructions for the experiment and an online
assignment to calculate the AOA with the given information.
At the beginning of the laboratory practical lesson, the students
were given 15 min to create a mind map with the topic
“Compounds in plants and their functions”. They could
supplement their mind maps with a different colored pencil at
the end of the lesson, which took 5 min. One week after the
experiment, the students answered for the second time the four
questions about the instrumentation with a 15 min time limit
and calculated the TPC in an online assignment.
■ SAFETY HAZARDS
Protective clothing, eyewear, and gloves should be used when
handling chemicals. Aqueous ethanol is flammable. Folin−
Ciocalteu reagent is an aqueous solution of inorganic
compounds. It is corrosive to metals and may cause severe
skin burns and eye damage. Sodium carbonate causes serious
eye irritation. DPPH is dissolved in ethanol. The powder may
cause allergy or asthma symptoms or breathing difficulties if
inhaled, and it may cause an allergic skin reaction.
■ RESULTS AND DISCUSSION
LC-MS Fingerprints and Defense Compounds of White
Birch and Silver Birch
Altogether, 103 leaf bud samples were analyzed in this study.
The LC-MS analyses were carried out during the laboratory
sessions, and students were able to identify their samples as
white birch, silver birch, or some other tree species. Here, 42%
of the samples were white birches, 43% were silver birches, and
the plant species of the rest of the samples remained unknown.
The university students analyzed samples that the instructor
had already identified, but the species was not revealed to the
students beforehand. All students were able to identify their
samples correctly with the LC-MS fingerprints.
The LC-MS fingerprints were presented as the combination
of SIR traces of ions with m/z of 365.0 and 439.6. Possible
structures are presented in Figure 2, and detailed information
about the compounds can be found in the Supporting
Information. The SIR chromatograms of theses ions showed
small variation in the shapes of the peaks, but all white birch
samples had one clear peak at 1.3 min (corresponding m/z
365.0), whereas silver birch samples had two peaks at 1.7 and
1.8 min (corresponding m/z 439.6) (Figure 3). However, the
method was not able to separate white birch from its
subspecies mountain birch (Betula pubescens ssp. czerepanovii)
that was included in the university students’ samples, as they
had identical fingerprints. In practice, that is a minor problem
since mountain birches have a narrow geographical distribu-
tion. The SIR chromatograms of samples that were not
identified as white birch or silver birch showed background
noise at low intensity.
Generally, the visual and spectrophotometric results for
AOA and TPC were lower for other leaf bud samples than for
white birch or silver birch (Figure 4). There was greater
variation in the results among the birch samples. In the
university students’ results, mountain birch samples (N = 5)
showed on average lower AOA and TPC than those of white
birch and silver birch samples. Silver birch samples (N = 17)
showed moderate bioactivity compared to that of mountain
birch and white birch samples. The two types of white birch
samples were from different trees at different times of the year.
The first type of white birch samples (N = 15) had higher TPC
and AA compared to the second type of white birch samples
(N = 13). The results from the colorimetric tests should be
considered only preliminary due to the substantial deviation
between the students’ results of samples from the same plant.
However, some of the deviation may be explained by biological
reasons, as, for example, the leaf buds are not all the same size.
The visual evaluations were in line with the spectrophoto-
metrically measured values.
Figure 2. Possible structures for the marker compounds used in the
LC-MS method.
Figure 3. Examples of LC-MS fingerprints of silver birch and white
birch leaf buds and an example of a sample that is neither. The LC-
MS fingerprint is the combination of two selected ion recording traces
of ions with m/z of 365.0 and 439.6.
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Despite the deviation in the results, the colorimetric and
spectrophotometric assays presented here are suitable for rapid
and simple screening of leaf bud samples. If the reagents would
be prepared and divided into tubes in advance, the extraction
and visual estimations of TPC and AOA could be performed in
the nature immediately after sample collection. The assays
showed that there are differences in the chemistry between
plant species and even between individuals. In addition, they
proved that going into the molecular level in plant chemistry
might be necessary if one wants to identify the plant species
utilizing chemistry. At the end of the laboratory session,
students were asked to compare their results with the
information on the identity of the plant species. They
concluded that the TPC and AOA values alone were not
sufficient information for identification. By identifying suitable
marker compounds from other tree species, the concept could
be expanded to other species as well.
University Students’ Understanding of the
Instrumentation
Different concepts regarding spectrophotometry, liquid
chromatography, and mass spectrometry in the university
students’ answers in the pre- and post-test were classified and
quantified, and a summary can be found in the Supporting
Information. The answers were examined from two perspec-
tives: whether they described (i) what the instrument measures
or what is the purpose of the instrument, and (ii) how it
functions. The goal was to estimate the students’ level of
knowledge before the laboratory experiment and how the
experiment changed students’ understanding of the instru-
mentation and methods used.
When comparing the pre- and post-test answers, the answers
improved in terms of what the instruments are used for, and
how the measurements are performed. The students connected
correct concepts with the instruments more often (Table 1).
Many of those concepts mentioned in the answers were rather
practical in nature, and showed the effect of the hands-on
experience of the laboratory work. For example, the students
mentioned a cuvette almost three times more often in the post-
test when describing the functioning of a spectrophotometer.
The post-test answers got somewhat more specific as well.
Instead of the general expression “produces ions”, the students
could describe in the post-test that an ion source converts
molecules into ions. Another practical improvement was seen
in how the students learned to utilize calibration curves. In the
prelab assignment, only 52% of the university students
calculated the AOA correctly. During the laboratory session,
98% of the students calculated the AOA of their own sample
correctly. In the postlab assignment, 82% of the students
calculated the TPC correct.
Figure 4. University students’ results of the (A) total phenolic
contents and (B) antioxidant activity assays.
Table 1. Number of the Most Common Correct Concepts in the Pre- and Post-test Answers
Instrument What It Does How It Functions
Pretest
(N = 53)
Post-test
(N = 53)
spectrophotometer measures absorbance/ability to absorb light 13 19
cuvette is used 7 20
light goes through the sample 14 23
liquid
chromatograph
separates substances 5 11
”organizes” the particles, they come out at
different times
0 7
polarity 0 8
ion source converts molecules into ions 1 15
a part of a mass spectrometer 1 17
mass spectrometer separates particles of different masses 7 14
detects a certain molecule 3 16
mass or m/z value of a particle 12 21
may function in many different ways 0 10
quadrupole 2 14
particles with the correct mass pass through, others
do not
4 16
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The pre- and post-tests also revealed, that the students had
several misconceptions regarding especially spectrophotometry
and liquid chromatography in terms of what they are used for,
while the ion source was linked to misconceptions about how
it functions (Table 2). In the pretest, 17% of the students
thought that a spectrophotometer is used to measure the
refractive index of a substance. Liquid chromatography was
confused with thin layer chromatography (TLC) by 23% of the
students, and additional 13% confused it with some other
instrument such as a centrifuge or a spectrophotometer. In the
post-test, some misconceptions were still present, but the
number of the most glaring misconceptions had decreased. A
refractometer or the refractive index was still mentioned in the
spectrophotometry answers, but only two students had made
the same mistake in both tests. In contrast, 83% of the students
that had described TLC instead of LC in the pretest answered
similarly in the question of LC in the post-test. Since these
students already had some basic knowledge of chromatog-
raphy, they could have benefited from comparing LC to TLC,
which might have improved their learning outcomes.
There were no clear misconceptions related to the mass
spectrometer in the pretest, but the answers were mainly
concentrated on mass analyzers. Since the question was not
defined to a specific mass analyzer, many students described a
sector instrument. Mass spectrometry is not included in the
first-year chemistry studies, so the students were not expected
to have consistent knowledge about mass spectrometry.
Therefore, the instructor accentuated during the laboratory
session that there are many different types of mass analyzers
that function in different ways. The basic functioning of both
the sector instrument and the triple-quadrupole instrument
was discussed with the students. In the post-test, magnetic field
and a sector instrument were mentioned as well. Unfortu-
nately, some answers were unclear in whether the instrument
described was a sector instrument or a triple-quadrupole mass
spectrometer. This observation highlights the importance of
recognizing students’ previous knowledge in mass spectrom-
etry. It might have been be difficult for the students to
understand the operating principle of a quadrupole mass
spectrometer (utilizes electric fields) if the primary mass
spectrometer for them is a sector instrument which utilizes
magnetic field as well.
In summary, the laboratory experiment provided university
students basic understanding of how the instruments function
and what they are used for. The students were rather
unfamiliar with the instruments beforehand and they would
have needed more time to develop a deeper understanding of
the chemistry and mechanisms behind the functioning of the
instruments. The pretest revealed some misconceptions about
the instruments, but the number of the most significant
misconceptions decreased in the post-test. However, the issues
about mass spectrometry and liquid chromatography in post-
test underlines the importance of recognizing students’
previous knowledge when introducing them new methods
and instruments.24,27
University Students’ Comprehension of the Chemistry of
Plants
University students’ mind maps contained on average 7.4
compounds and compound groups, and 5.2 biological
functions at the beginning of the laboratory session. The
occurrence of different compound groups and biological
functions connected to them are summarized in the
Supporting Information. The majority of the compounds
were related to photosynthesis (on average 3.0 per mind map).
Other primary metabolites were rarer (only 1.7 per mind
map). Specialized metabolites such as phenolic compounds,
pigments and toxins were present in small numbers before the
laboratory experiment. Figure 5 shows the frequency of
different compound groups in the students’ mind maps.
The most common compounds were water and sugars,
which were present in 64% and 74% of the answers,
respectively. The functions of these compounds were typically
connected to photosynthesis. Out of other primary metabo-
lites, cellulose and nutrients were mentioned most frequently
(38% and 32% of the mind maps in total, respectively). The
task of cellulose was most often related to the physical
structure of plants and in 17% of the mind maps more
specifically even to the cell walls. Nutrients, however, were the
most often left without functions. After the laboratory session,
only few modifications or additions were done in primary
metabolites either as new compounds or new functions. Only
water and glucose were connected with new functions. This
was an expected result, since the primary metabolites or
photosynthesis were not discussed during the laboratory
experiment.
On average, students added 1.6 new compounds and 1.6
new biological functions to their mind maps, usually regarding
phenolic compounds and antioxidants. Before the laboratory
Table 2. Number of Different Misconceptions in the Pre- and Post-test Answers
Instrument What It Does How It Functions Pretest (N = 53) Post-test (N = 53)
spectrophotometer measures the refractive index 9 8
is based on the refraction/scattering of light 6 2
measures the wavelength 3 1
LC described 0 3
liquid chromatograph separates liquids/phases 5 3
measures density 1 0
TLC described 12 14
centrifuge described 3 0
spectrophotometer described 2 1
refractometer described 2 3
ion source a certain substance does the ionization 5 2
ionization is based on radiation 4 2
ionization is performed through an ion beam 0 2
ionization happens in the quadrupole 0 3
mass spectrometer no clear misconceptions detected
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session, these types of compounds were mentioned in 23% and
19% of the mind maps, respectively. After the laboratory
session, the numbers were 89% and 60%. Also, the number of
functions for these compounds increased markedly. Before the
laboratory experiment, the function connected to phenolic
compounds was defense mechanism. After the laboratory
experiment, students described more specifically that phenolic
compounds protect plants from herbivores (53% in total) and
UV radiation (34% in total). The most common function
connected to antioxidants before and after the laboratory
experiment was protection from oxidation.
Interestingly, antioxidants were presented as separate nodes
in some mind maps (Figure 6A). Generally, all antioxidants are
not phenolic compounds, but in the context of this laboratory
experiment the observed antioxidant activity is presumably
caused by the phenolic compounds.11 The separate nodes with
different functions suggested that some students perceived
antioxidants and phenolic compounds as separate groups of
compounds, and this issue should be considered when
discussing the results with the students. In contrast in Figure
6B, antioxidants and phenols share the same node and the
same function. Moreover, it showed how these specialized
metabolites differ from primary metabolites: they may be
different in different plant species.
The results suggested that the laboratory experiment was
able to broaden students’ view of the chemistry of plants by
adding a new class of compounds, that is, specialized
metabolites. Both mind maps in Figure 6 are excellent
examples of that. The experiment also made students connect
the chemistry to the biology of plants, that is, the functions of
the different compounds in plants. Thus, the use of an
interdisciplinary approach seemed to support student in
creating a more “authentic big picture” of scientific research.23
Feedback
University students estimated their understanding and interest
by rating how strongly they agreed or disagreed with the
statements of the feedback survey on a five-point Likert scale
(Supporting Information). The statements were categorized
into five main themes:
(1) statements that measured students’ interest in the
instruments,
Figure 5. Different compound groups in the university students’ mind
maps before the laboratory experiment. The size of the slice is
proportional to the frequency of the compound in the mind maps.
Figure 6. (A) Example of a mind map where phenolic compounds and antioxidants have been presented as separate nodes. (B) Typical mind map
with mostly primary metabolites, but antioxidants and phenols presented in the same node. Students were asked to use red color in the markings
they made after the laboratory experiment.
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(2) interest toward the research aspects (for example, “I am
interested in how research in chemistry is carried out”),
(3) interest toward the topic of the experiment,
(4) enjoyment of the concrete and practical aspects of the
experiment, and
(5) understanding of the different phases of the exper-
imental procedure.
Overall, students’ responses in all categories were very
positive. Students found especially the topic and research in
chemistry interesting (Figure 7). They also appreciated the
concrete hands-on parts of the experiment. The lower average
value for interest toward the instruments is mainly due to the
statement “I would have wanted to use the LC-MS instrument
independently.” Here, 32% of the students agreed with the
statement, 42% of the students disagreed, and the rest of the
students chose the option in between. However, 79% of the
students found it interesting to be able to analyze their own
sample with the LC-MS instrument. For the majority of the
students, it seemed that giving a short introduction and the
possibility to analyze their own sample was enough when they
utilized LC-MS for the first time. According to the students’
evaluation, they understood well what happened during the
experiment. The hardest part to understand was how the
fingerprint LC-MS method works.
Secondary school students were asked to choose their
favorite part of the experiment. The majority (59%, N = 69) of
the students chose the Folin−Ciocalteu and DPPH assays as
their favorite part. They enjoyed mixing the solutions, seeing
the colors change, and using pipettes. The LC-MS analysis was
the favorite part for 26% of the students either because it
revealed the birch species, they found the instrument “cool” or
they enjoyed hearing how it works. Overall, the students
enjoyed working with the laboratory facilities, from syringes
and filters to pipettes and actual measuring equipment. These
are such tools that are not used regularly at school laboratories,
which might explain why the students got excited about them.
It also suggested that this laboratory experiment was successful
in providing an authentic laboratory experience to them. For
example, one of the students wrote the following feedback: “It
was cool to work at the university, we got to learn what people
actually do at the university and we learned new things.”
In summary, the results showed that both the university and
the secondary school students appreciated the opportunity to
work hands-on with state-of-the-art research instruments. To
support students’ interest in chemistry and their understanding
of the role of instrumentation in chemical research,25,26 there
might be a need for creating even more opportunities for
gaining hands-on experiences on the use of modern instru-
ments both in university and secondary education.27 Also, the
students found the topic interesting as in other publications
utilizing interdisciplinary contexts.14,18,21
■ CONCLUSIONS
The laboratory experiment was successfully conducted with
lower and upper secondary school students as well as with first
year university students. It was modified to fit the different
time slots booked by the groups by altering the number of
samples that the students analyzed, and whether a spectropho-
tometer was used in addition to the visual evaluations. It
provided tools to show how birches differ from each other
chemically. With the novel LC-MS method, the birch species
could be identified in less than 4 min. With the colorimetric
tests, students evaluated the TPC and AOA of their extracts
and were able to calculate the AOA and TPC using calibration
curves. With these methods they could also make conclusions
of the chemical defense of plants. As the mind maps showed,
students were able to connect the defense compounds
(chemistry) to their functions in plants (biology). The
experiment provided students a basic understanding of how
a spectrophotometer and UHPLC connected to a triple-
quadrupole mass spectrometer work. Finally, the students
enjoyed the colorful TPC and AOA tests, and although the
mass spectrometric part was the hardest to understand,
students appreciated the possibility to analyze their own
samples and explore the instrument.
■ ASSOCIATED CONTENT
*sı Supporting Information
The Supporting Information is available at https://pubs.ac-
s.org/doi/10.1021/acs.jchemed.0c00589.
Background information, materials and protocols, addi-
tional information on the marker compounds, pre- and
postlab tests and assignments, and summaries of
students’ responses (PDF, DOCX)
Student instructions (PDF, DOCX)
■ AUTHOR INFORMATION
Corresponding Author
Marianna Manninen − Natural Chemistry Research Group,
Department of Chemistry, University of Turku, FI-20014
Turku, Finland; orcid.org/0000-0003-3102-7188;
Email: marianna.i.manninen@utu.fi
Authors
Veli-Matti Vesterinen − Department of Chemistry, University
of Turku, FI-20014 Turku, Finland; orcid.org/0000-
0002-1255-6845
Anna-Kaisa Vainio − Department of Chemistry, University of
Turku, FI-20014 Turku, Finland; Raisio Senior High School,
FI-21200 Raisio, Finland
Heidi Korhonen − Department of Chemistry, University of
Turku, FI-20014 Turku, Finland; orcid.org/0000-0001-
6974-9907
Figure 7. Average grades and standard deviations of students’ (N =
53) responses in the feedback survey of how interesting they found
the different aspects of the laboratory exercise and how well they
understood the protocols; 1 = disagree totally; 5 = agree totally.
Journal of Chemical Education pubs.acs.org/jchemeduc Laboratory Experiment
https://dx.doi.org/10.1021/acs.jchemed.0c00589
J. Chem. Educ. 2021, 98, 973−981
979
Maarit Karonen − Natural Chemistry Research Group,
Department of Chemistry, University of Turku, FI-20014
Turku, Finland; orcid.org/0000-0002-9964-6527
Juha-Pekka Salminen − Natural Chemistry Research Group,
Department of Chemistry, University of Turku, FI-20014
Turku, Finland; orcid.org/0000-0002-2912-7094
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.jchemed.0c00589
Notes
The authors declare no competing financial interest.
■ ACKNOWLEDGMENTS
We would like to thank the students for participating in the
study, and their teachers Henri Kivela,̈ Marjo Numminen,
Virpi Pihlaja-Niinistö, Karoliina Salmenpera,̈ Petri Taḧtinen,
and Marianna Vanhatalo for the arrangements that made
students’ participation possible. This work was financially
supported by Turku University Foundation and Finnish
Cultural Foundation (research grants for M.M.). The Strategic
Research Grant (Ecological Interactions) enabled the purchase
of the UPLC-DAD-MS/MS instrument.
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