Laboratory Experiment
Cite This: J. Chem. Educ. 2018, 95, 451−455
pubs.acs.org/jchemeduc
Quantitative Determination of Aluminum in Deodorant Brands: A
Guided Inquiry Learning Experience in Quantitative Analysis
Laboratory
Victoria Sedwick, Anne Leal, Dea Turner, and A Bakarr Kanu*
Department of Chemistry, Winston-Salem State University, Winston-Salem, North Carolina 27110, United States
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S Supporting Information
*
ABSTRACT: The monitoring of metals in commercial
products is essential for protecting public health against the
hazards of metal toxicity. This article presents a guided inquiry
(GI) experimental lab approach in a quantitative analysis lab
class that enabled students’ to determine the levels of
aluminum in deodorant brands. The utility of a GI
experimental lab introduced in the quantitative analysis lab
class as part of an active learning hands-on-experience
approach enhances student learning, improves students’ critical
thinking and problem solving skills, and motivates underrepresented students to work independently in solving a real-world scenario-type problem. Students were required to develop
certain lab skills at the start of the semester and apply these skills toward the end of the semester to investigate the GI project.
The GI project that analyzes for aluminum improves the overall student engagement, enthusiasm for the quantitative analysis
laboratory course, and even the overall success rate in scientific report writing.
KEYWORDS: Upper-Division Undergraduate, Hands-On Learning/Manipulatives, Inquiry-Based/Discovery Learning,
Laboratory Instruction, Interdisciplinary/Multidisciplinary, Problem Solving/Decision Making, Consumer Chemistry,
Quantitative Analysis
■
INTRODUCTION
Guided inquiry (GI) method of instruction in the laboratory1−8
has been shown to be effective for enhancing students’
achievement9 in the classroom. GI lab approach can be
considered as an active learning strategy10−13 capable of
advancing critical-thinking and problem-solving skill sets for
science, technology, engineering, and mathematics (STEM)
education.14−22 In this article, a GI experimental lab designed
to investigate aluminum content in deodorant brands was
incorporated in a quantitative analysis lab class. At the
beginning of the semester, the instructor designed and
introduced targeted laboratories geared toward improving the
skill set for each student. The skills sets incorporated in the
targeted laboratories were the following: safety practices in the
lab, best practices for maintaining laboratory notebook, sample
preparation techniques, processing data using Microsoft Excel,
statistical analysis of experimental data, experimental design,
proper use of equipment, interpretation of experimental data to
reach a valid conclusion, and writing detailed scientific reports.
At the end of the skills enhancement period, students’ break
away from their teams and worked independently to investigate
the GI problem presented to them.
Aluminum is the most abundant metal in the earth’s crust. It
is a very reactive metal and is capable of combining with several
other elements. Aluminum metal is light in weight and silverywhite in appearance. Aluminum is found in many consumer
© 2018 American Chemical Society and
Division of Chemical Education, Inc.
products including antiperspirant and deodorants. Oral
administration of Al is not harmful. However, some studies
have shown that people exposed to high levels of aluminum
may develop Alzheimer’s disease, but other studies have not
found this to be true.23 People with kidney disease store a lot of
Al in their body. Kidney disease causes less aluminum to be
removed from the body in the urine.23 These individuals may
developed bone or brain diseases that doctors think may be
linked to excess aluminum. Aluminum containing over-thecounter oral products are considered safe in healthy individuals
at recommended doses. However, some adverse effects have
been observed following long-term use in some individuals.
Children with high levels of Al in their body and suffering from
kidney disease have been shown to suffer from brain and bone
diseases. The bone damage may have been caused by aluminum
in the stomach preventing the absorption of phosphate, a
chemical compound required for healthy bones.23 With all
these problems, it may be necessary to develop a method for
evaluating Al in commercial products.
A deodorant or antiperspirant is a common commodity in
every household. It is typically used once or twice a day
depending on how much a person sweats, but is it actually safe?
Received: May 22, 2017
Revised: December 10, 2017
Published: January 19, 2018
451
DOI: 10.1021/acs.jchemed.7b00336
J. Chem. Educ. 2018, 95, 451−455
Journal of Chemical Education
Laboratory Experiment
chlorohydrate (ACH) compound (Al2Cl(OH)5, FW = 174.45
g/mol)23,26,27 were investigated as follows; 10 mL of deodorant
sample, 30 mL of EDTA, and 5.00 mL of pH 4 buffer were
added to a 150 mL Erlenmeyer flask. The mixture was heated
on a hot plate at 250−300 °C for approximately 15−20 min or
until the solution began to boil. The mixture was then allowed
to cool at room temperature. To start the titration, 5−6 drops
of Eriochrome Black T indicator was added to the solution to
give it a purple color. The mixture was titrated with 0.01 M
ZnSO4 until it turned a permanent shade of pink. The shade
varied with the temperature of the solution and the amount of
indicator added. Seven replicate titrations were performed for
each deodorant.
The primary purpose of deodorant or antiperspirant is to keep
the areas applied to in the body dry, thus the name. The
primary ingredient that contributes to this purpose is aluminum
in the form of either aluminum zirconium trichlorohydrex
GLY24 (AZG) or aluminum chlorohydrate (ACH).23 To block
perspiration, aluminum clogs sweat ducts in the areas to which
it is applied. This makes the ducts swell as they are filled with
water. Aluminum is not an element that resides naturally in the
human body. Therefore, analytical methods should be
developed to determine its content in commercial products
such as deodorants.
The purpose of this GI experimental lab was to determine
the presence and quantity of aluminum in different brand
deodorants. To address this problem, ethylene diamine
tetraacetic acid (EDTA) was employed in a back-titration
approach with Zn2+ ions. The back-titration approach was
chosen by the students because Al is capable of blocking the
indicator if a direct titration is employed. In this study, we
measured the levels of Al in deodorant brands to see if actual Al
content matches the label.
■
■
HAZARDS
Undergraduate students were initially shown the American
Chemical Society (ACS) safety video before conducting any
experimental work in the laboratory. The students wore safety
goggles and gloves at all times in the laboratory and were
instructed to handle concentrated acids with great care because
of their corrosive nature. For activities involving these
concentrated acids, including sample preparation, it was
recommended that undergraduate students work in pairs and
under close supervision.
EXPERIMENTAL SECTION
Experimental Lab Design
■
The student enrollment in the quantitative analysis laboratory
course, fall 2015, was made up of 12 African American and 1
Caucasian, a total of 13 students, 18−27 years old. Female
enrollment for the fall 2015 class accounts for 70% of the class.
At the start of the semester, students were divided into five
groups of two and one group of three. This was necessary to
promote teamwork among the students. The teams worked on
ten targeted laboratories designed by the instructor to improve
the analytical skills set of each student. Skills developed during
the targeted laboratories period includes: safety practices in the
lab, best practices for maintaining laboratory notebook, sample
preparation, processing data in Microsoft Excel, statistical
analysis of experimental data, experimental design, proper use
of equipment, interpretation of experimental data to reach a
valid conclusion, and writing detailed scientific reports. At the
end of the skills enhancement period, the groups were dissolved
and each student was encouraged to work independently to
complete the GI project. Before groups were dissolved, the
entire class conducted literature review on the GI project and
brainstormed on how to analyze deodorants for aluminum. The
discussions led to the decision that sodium ethylene diamine
tetraacetic acid (Na2EDTA) should be used to conduct the
analysis through back-titration with zinc sulfate. After the
deliberation, each student chose a deodorant brand and
designed the experiment on their own to complete the analysis.
The entire project including scientific report writing lasted for 5
weeks, and students were required to meet with the instructor
each week to discuss their progress. The students’ requested all
supplies they needed, designed their buffer solution, and
prepared their own samples. At the end of the project, each
student was required to submit a detailed scientific report for
her or his analysis.
RESULTS AND DISCUSSION
Aluminum Content in Deodorant Brands
Several EDTA titration techniques exist. The titration
procedure employed for this investigation was designed to
follow a back-titration approach because Al under investigation
has a capability of blocking the indicator in the titration
process.28 Back titration may also prevent precipitation of Al.
For example, Al(OH)3 precipitates at pH = 7 in the absence of
EDTA. Boiling the solution was also necessary for the titration
process to ensure complete formation of stable, soluble
Al(EDTA)− complex. The metal ion for back-titration must
not also displace Al from EDTA.28 This was the reason why
Zn2+ was chosen for the back-titration.
Table S-1 (see Supporting Information) shows information
for each deodorant which includes the total mass for each
deodorant brand and the percent of AZG or ACH present in
the sample. For example, Dove Powder deodorant has a total
mass of 74 g, 18.20% AZG, and 0.00% ACH. Only one of the
deodorant samples (soft and dri) contained 0.00% AZG and
ACH. Table S-2 (see Supporting Information) shows the mass
of deodorant measured to prepare each stock solution and the
total volume of solution of stock solution for each deodorant
brand.
Table S-3 (see Supporting Information) summarizes the
result for the titration (n = 7) and shows the moles of EDTA,
moles of ZnSO4 required to react with excess EDTA, the moles
of Al3+ present in the stock solution of each deodorant brand,
and the mass of Al3+ present in the total deodorant brand.
As an example, 2.1152 g of Lady Speed Stick deodorant was
measured and prepared as a stock solution of 250 mL (Table S2). This solution contained 9.30 × 10−4 moles Al3+ (Table S-3).
The total mass of Lady Speed Stick was 39.6 g (Table S-1).
This mass of Lady Speed Stick deodorant contained 0.47 g of
Al3+ (Table S-3).
Table 1 summarizes the weight percent (% wt) Al3+ from
each deodorant brand, the 99.9% confidence interval (CI), the
theoretical % wt of Al3+ in each deodorant brand and the
Titration Analysis
The titration process was performed as follows: deodorants that
contained aluminum zirconium tetrachlorohydrex Gly (AZG)
compound (Al2Cl7H7O7Zr2, FW = 603.64 g/mol)24,25 were
investigated as follows; 15 mL of deodorant sample, 30 mL of
0.01 M EDTA, and 5.00 mL of pH 4 buffer were added to a 150
mL Erlenmeyer flask. Deodorants containing the aluminum
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DOI: 10.1021/acs.jchemed.7b00336
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Laboratory Experiment
Table 1. Comparative Analysis of Weight Percent of Al3+
from Different Deodorant Samples
Sample Source
Experimental Al3+
% wta
99.9%
CIb
Theoretical Al3+
% wtc
Error,
%d
1.54
0.00
1.19
±0.37
5.52
±0.61
1.63
0.00
1.38
13.77
8.85
±1.86
5.57
58.89
1.72
1.60
1.73
±0.65
±0.59
±0.35
1.61
1.63
1.63
6.83
1.84
6.13
5.80
1.39
±0.72
±0.33
6.19
1.43
6.30
2.80
Dove Powder
Soft and Dri
Lady Speed
Stick
Ban Powder
Free
Old Spice
Men Degree
Women
Degree
Mitchum
Right Guard
a
Experimental weight percent of Al3+ obtained for the deodorant
brand (n = 7). b99.9% confidence interval (CI, n = 7). cTheoretical
weight percent of Al3+ calculated using either Al2Cl7H7O7Zr2 (AZG)
or Al2Cl(OH)5 (ACH) in deodorant sample (n = 7). dCalculated
using eq S-10.
Figure 1. Example image of students working on a guided-inquiry
project in a quantitative analysis lab class, fall 2015.
in situations where they have to apply skills developed early on
in the semester. In addition, efforts were made to assess the
impact of the experiment on students’ perception, attitudes, and
overall success in the GI project. In the past few years, the
instructor teaching this course has collaborated with undergraduate students by encouraging them to suggest analytical
problems they would like to investigate. Thus, a student initially
suggested the GI project reported in this article. At the
conclusion of the project, all students were required to write
and submit a full scientific report for assessment by the
instructor. The data from submitted reports for the GI
laboratories shows that students’ results demonstrated consistency between replicate measurements. The reports were
assessed and the results are shown in Figure 2. In general, for
percent error for the analysis. The steps used to calculate these
values are shown in the Supporting Information. The
experimental % wt values of Al3+ for Dove Powder, Soft and
Dri, Lady Speed Stick, Ban Powder Free, Old Spice, Degree
Men, Degree Women, Mitchum, and Right Guard were 1.54 ±
0.37%, 0.00 ± 0.00%, 1.19 ± 0.61%, 8.85 ± 1.86%, 1.72 ±
0.65%, 1.60 ± 0.59%, 1.73 ± 0.35%, 5.80 ± 0.72%, and 1.39 ±
0.33%, respectively. A higher CI was used (99.9%, n = 7, t =
5.959) to provide more reliability on the range of the true % wt
Al3+. For example, the % wt Al3+ in men degree was 1.60 ±
0.59%. This tells us that we are 99.9% confident that the true
Al3+ %wt falls between 1.01 to 2.19%. To determine the percent
error for the analysis, the theoretical Al3+ % wt was calculated
using eq S-9 (see Supporting Information for all other
equations) and information from the deodorant product. This
information was then used to calculate the percent error
according to eq S-10 (see Supporting Information), and shown
below.
percenterror =
|E% wt − T% wt |
× 100%
T% wt
(S−10)
where E%wt is the experimental % wt and T%wt is the theoretical
% wt.
The percent errors for the titration process are shown in
Table 1. For the Ban Powder Free deodorant, Old Spice, and
Degree Women, the results shows that the amount of Al
content from the titration process exceeded that reported on
the label. In addition, the high percent error shown for Ban
Powder Free was a result of the experimental % wt Al3+ was
much higher than the theoretical % wt Al3+.
These results further demonstrates that GI projects in
laboratory settings proved to be effective for improved student
achievements.9 The approach used here required students to
solve a real-world problem and they have to demonstrate
understanding of skills developed earlier on in the semester to
be successful with the project.
Figure 2. Comparison of students’ lab grades for GI and non-GI
laboratories.
fall 2015 GI lab (n = 13), 46% of the students scored between
90 and 100%, 31% scored between 80 and 90%, and 23%
scored between 70 and 80%. To use fall 2015 non-GI lab (n =
13) as an example, 8% of the students scored between 90 and
100%, 23% scored between 80 and 90%, 23% scored between
70 and 80%, 15% of the students scored between 60 and 70%,
and 8% of the students scored between 50 and 60%. A similar
data summary showing improvement in scientific report writing
grades for fall 2016 is also shown in Figure 2. These GI lab
grades were a significant improvement when compared to the
Evaluation and Informal Feedback
The student feedback from the quantitative analysis class was
generally very positive. Figure 1 is an example picture of
students working on their project in the quantitative analysis
class, fall 2015. The experiment ensured students were placed
453
DOI: 10.1021/acs.jchemed.7b00336
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Journal of Chemical Education
Laboratory Experiment
Figure 3. Comparison of survey results concerning anxiety due to using chemicals, preskills enhancement for GI lab, recording experimental data,
and overall experience in a GI lab.
Implementing techniques in quantitative analysis type
settings such as hand-on-experience, problem solving, critical
thinking, independence, and communication skills in GI
laboratory experience are highly desirable to advance and
sustain learners’ academically and professionally in future
science careers.
majority of other laboratories where a GI approach was not
implemented.
The perception of students toward GI lab was further
evaluated by administering a survey designed around the
Dalgety’s et al. Chemistry Attitude and Experiences Questionnaire (CAEQ). Completion of the survey was voluntary,
and written informed consent was obtained from all
participants. Figure 3 shows the results of four questions
posed to the students.
The survey also allowed participants in the quantitative
analysis class to provide open-ended feedback on their GI lab
approach compared to traditional “cookbook” experiments
where students simply followed a laboratory procedure. Some
of the specific comments from two participants include: “At
first, the GI lab investigation was difficult and the concept did
not solidify completely with me. After reviewing the concept
and the connection between the targeted lab reports and the GI
project, the way forward becomes clearer to me.” “The GI
experiment helped me to view things from a scientific
perspective because what we may have worked on with
previous labs may not work for you, so it causes you to think of
other ways to get better results.”
The students further identified the five-week GI lab in which
they analyzed for Al in a commercial product as their best
experience for the semester and identified the approach as
being very different form other laboratories. Majority of the
students particularly liked the idea they were in charge of their
experiment and enjoyed the freedom to review the literature
and think through most of the problems they encountered with
minimum supervision. They were also very excited to have
played a role in the GI topic selection for the semester. They
reported that this motivated them to be accurate and made
their experience more worthwhile. Some students reported that
the GI lab experience in quantitative analysis motivated their
interest in a research career.
■
CONCLUSION
This manuscript reports on the introduction of a GI lab in a
quantitative analysis class that analyzed for Al contents in
deodorant brands. The GI lab approach used here required
students to solve a problem encountered in their everyday lives.
This article demonstrated that utilizing GI lab approach has a
direct relationship to improving students’ critical thinking, and
problem solving skills. Most students enrolled in the
quantitative analysis class had no previous knowledge on how
to develop an experimental strategy and execute the strategy to
solve a real-life problem. The results communicated in this
article demonstrated that students can develop as well as apply
skills to solve problems if the right scenario is setup for them.
By offering a lab course that allowed students to develop
specific skills during the semester, it may prove beneficial when
these students are placed in situations where they can apply
their knowledge. Other studies have documented that teamwork in a chemistry laboratory has advantages such as
promoting individual responsibility from students, ensuring
collective responsibility in a laboratory setting, as well as
allowing students to learn from their group members. However,
other students have reported they did not like group work
especially in situations where all responsibility is left to one
member of the group. We have noted that the approach used in
this GI lab; improving students’ skill sets and encouraging them
to participate individually in situations where they can apply
skill sets learned previously may promote critical thinking,
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problem solving, and independence of each student in a
classroom environment. Students’ feedback to the approach
was overwhelmingly positive. The GI lab introduced herein
used an approach that initially introduced skills enhancement
with structured assessments to develop the theoretical and
technical skills set of the students. Applying learned skill sets to
solve real-life problems in a GI-type lab approach may assist
students in informed choices for their future career in the
sciences.
■
ASSOCIATED CONTENT
S Supporting Information
*
The Supporting Information is available on the ACS
Publications website at DOI: 10.1021/acs.jchemed.7b00336.
Materials and reagents; preparation of standards;
calculations; supporting tables; notes to students and
faculty (PDF, DOCX)
■
AUTHOR INFORMATION
Corresponding Author
*E-mail: kanuabb@wssu.edu. Phone: +1 336-750-3199.
ORCID
A Bakarr Kanu: 0000-0002-0869-3310
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
We gratefully acknowledge the support of the Research
Initiation Program and Professional Development Committee
at Winston-Salem State University for their support of this
work. The authors also thank David Pollard and the Analytical
Sciences Digital Library (ASDL) Active Learning Workshops
for their support during this investigation.
■
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