Introduction
Quinine is a basic organic amine which is found in the bark of cinchona tree. It has a long history of relationship with humanity. The extracts from the bark containing quinine were used to treat malaria from the 17th century but as a pure chemical substance, it was isolated from the bark only in 1820 (Achan et al. 144). Its chemical formula is C20H24N2O2, according to IUPAC its systematic name is (R)-(6-Methoxyquinolin-4-yl)((2S,4S,8R)-8-vinylquinuclidin-2-yl)methanol. Its structure is shown in Fig. 1.
Quinine is used for a variety of purposes. It is still used for medical purpose as it was used centuries ago. Its main field of medical application consists in malaria treatment. For a long time, quinine was recommended by WHO as one of the most important medications.
However, we all know quinine much better for it’s the bitter taste it gives to the beverages. Quinine beverages originated from its use as a medicine and were very bitter initially but became milder over time and transformed into the beverage we now know as tonic water.
Quinine is also used for scientific purpose. It is used as a fluorescence standard in photochemistry for its well-known and constant fluorescence quantum yield. It is also used as a chiral ligand in various syntheses such as Sharpless asymmetric dihydroxylation.
It may be tempting to think that tonic water may be used to treat malaria but in reality it would be rather troublesome. Quinine daily dose for malaria treatment is from 700 to 1050 mg while in regular 12-oz bottle of tonic water there is around only 40 mg (Bryner). Moreover, in certain countries, such as U.S. and Germany, quinine concentration in soft drinks is regulated. It is limited to 83-85 ppm (Linskens and Biehl 166).
The purpose of this experiment was to determine quinine concentrations in ppm in several brand name tonic water using molecular fluorescence method. The drinks used were schwepps, regular vintage tonic water, diet tonic water, and canada dry.
Results
The emission of prepared standards is presented in the Tab. 1. The corresponding calibration curve is shown in Fig. 2:
Figure 2. Calibration Graph
The emission of the investigated tonic water sample comprised 31.960. Using the equation of the calibration curve, the concentration of quinine in the sample with unknown concentration is found
31.96014.72 = 2.17 ppm.
The investigated tonic water was diluted for the experiment (1 ml of beverage to 25 ml test solution), so the concentration of quinine in original beverage is
2.17 ppm×25 mL1 mL=54.25 ppm
Conclusion
The experiment was successful and the concentrations of quinine in ppm in different brands of tonic water were found. Regular vintage tonic water was investigated by our team. The concentration of quinine in the beverage was found using molecular spectrometry. The experiment showed that the concentration of quinine in the mentioned drink was 54.25 ppm which lies in line with governmental regulations of quinine concentration in beverages. Possible source of error was experimental error.
References
Achan, Jane et al. "Quinine, An Old Anti-Malarial Drug In A Modern World: Role In The Treatment Of Malaria". Malar J 10.1 (2011): 144. Web. 15 May 2016.
Bryner, Michelle. "What Is Quinine?". Live Science. N.p., 2014. Web. 15 May 2016.
Linskens, Hans F and Böle Biehl. Analysis Of Nonalcoholic Beverages. Berlin [u.a.]: Springer, 1988. Print.
New World Encyclopedia. Quinine Skeletal. 2008. Web. 15 May 2016.
