The QB3/College of Chemistry Mass Spectrometry Facility has partnered with IISME (Industry Initiatives for Science and Math Education) and SynBERC (Synthetic Biology Engineering Research Center) to provide a summer fellowship to a high school science teacher. During the last two summers, the facility has hosted Jonathan Fong from Lowell High School in San Francisco. Mr. Fong has developed a program using GC/MS (Gas Chromatograph/Mass Spectrometry) to determine the amount of caffeine in soft drinks.
A video of students from Lowell High School preparing their samples for GC/MS is presented here.
How Much Caffeine Is in My Soft Drink?
Determination of Caffeine Content in Soft Drinks Using GC-MS
- To use chemical separation techniques to detect caffeine in soft drinks.
- To apply knowledge of solubility, molecular polarity, and density to explain separation techniques.
- To determine caffeine content in soft drinks by analyzing gas chromatography/ mass spectrometry data.
Caffeine is added to many soft drinks and energy drinks. Soft drinks differ from energy drinks in that soft drinks are regulated by the FDA and are limited in how much caffeine they can contain, whereas energy drinks are not. Some of the effects of human consumption of caffeine are well known to most high school students. From the National Institutes of Health: Excessive caffeine intake can lead to a fast heart rate, excessive urination, nausea, vomiting, restlessness, anxiety, depression, tremors, and difficulty sleeping. The effect of caffeine on health has been widely studied.
In this experiment, we will use reagents commonly found in a high school chemistry laboratory to isolate caffeine from a soft drink or energy drink into a solvent suitable for GC/MS analysis. Most solvents commonly used in caffeine isolation are carcinogenic. However, in this experiment, we will use 70% rubbing alcohol (a.k.a. isopropanol or 2-propanol) since it is easily obtainable and safe to use in a high school laboratory. The caffeine will be isolated using knowledge of density, molecular polarity, and solubility.
Using GC-MS, you will determine the amount of caffeine extracted from your soft drink. Deuterated caffeine will be used as an internal standard. Deuterated caffeine is structurally similar to caffeine, except that it contains 3 atoms of deuterium, or a hydrogen atom with an extra neutron. A known amount of deuterated caffeine (100 micrograms) will be added to your soft drink prior to the separation and analysis procedure. When analyzing caffeine using GC/MS, the concentration of caffeine is directly proportional to the area under the chromatographic peak. If you know the concentration of one substance and have the areas under each peak for both substances, you can solve for the concentration of the second substance to determine the amount of caffeine in the soft drinks. Students will prepare their samples following the protocol developed by Mr. Fong. The samples should be mailed to the Mass Spectrometry Facility for analysis, and the results will be returned to the teacher. High school chemistry teachers interested in pursuing this experiment for their class should contact Dr. Ulla Andersen for additional information.
The GC/MS (Autospec mass spectrometer equipped with an Agilent GC) used for this project was purchased with a grant (0741839) obtained from the National Science Foundation. IISME provided the organizational support while SynBERC provided financial support for Mr. Fong.