Providing training through guided-inquiry experiments in analytical chemistry or active learning including hands-on activities in a classroom environment for STEM students is a critical and effective strategy in today’s competitive global economy. This strategy has been reported to be an effective teaching method for engaging undergraduate students in a classroom environment. To advance the progress of STEM education, it is critical to employ critical-thinking and problem-solving skill sets for our future science students. A guided-inquiry experiment designed for a quantitative analysis class was used to determine the aluminum content in several deodorant brands. Al is the main antiperspirant component in several deodorant brands. Al has also shown potentials to present some toxicity in the human body. It is important to know the levels of intake from deodorant brands on a daily basis. The Al content was investigated in a back titration experiment using EDTA. Approximately 15 mL of prepared deodorant sample, 30 mL of EDTA, and 5 mL of pH 4 buffer was added to a 150 mL Erlenmeyer flask. The mixture was heated on a hot plate at 150 degrees for approximately 15-20 minutes. After heating, the solution was allowed to cool to room temperature. 5-6 drops of Eriochrome Black T indicator was then added. The resulting solution was titrated with 0.01 M ZnSO4. Seven replicate measurement was made for each deodorant sample. Weight percent of Al was calculated for each deodorant brand studied. The lowest weight percent of 1.19 ± 0.27% (m/m) Al was determined in Dove Powder 24h invisible solid with an error of 14%. At the 99.5% confidence interval, the mean present a lower confidence limit of 0.75% and an upper limit of 1.63%. The highest weight percent of 5.80 ± 0.32% (m/m) Al was determined in MitchumTM Advance Control deodorant brand for men with an error of 6%. At the 99.5% confidence level, the mean present a lower confidence limit of 5.28% and an upper limit of 6.32%. These results demonstrates that such experimental design can be applied to other cosmetic products in order to determine the quantity of potentially harmful ingredients delivered into our body. Guided-inquiry experimental approach for analytical chemistry classes has the capability to enhance student learning and improved students’ critical and problem-solving ability. Such experimental approach may strengthen undergraduate chemistry programs and improve as well as facilitate overall student learning.

Quantitative determination of aluminum in eight deodorant brands

253rd National Meeting (2017)

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