Introduction The purpose of this experiment was to determine the content of various over-the-counter analgesics using thin-layer chromatography.
Experiment Scheme Equation 1:
Near the bottom of a TLC plate, a small amount of a known analgesic was spotted about 1.0 cm away from the bottom of the plate along with a reference spot for the control. This was repeated on another plate using unknown analgesics. The plates were then placed in a jar of solvent to develop, where only the bottom of the plates were submerged. Once the solvent reached about 0.5 cm from the top, the plates were removed from the jar and the solvent front was marked on each. The plates were then observed with a UV light where spots were observed and sketched onto the plates. The retention factor (Rf) was then determined by measuring (in millimeters) the distance each spot had traveled relative to the solvent front. An iodine analysis was also done by placing the plates in a jar of iodine crystals until spots began to appear. The visibility and relative color of each spot was observed.
Data
Name | Formula | MW(g/mol) | Hazards | acetaminophen | C8H9NO2 | 151.17 | Irritant, harmful if excess swallowed. | aspirin | C9H8O4 | 180.16 | Irritant, harmful if excess swallowed. | caffeine | C8H10N4O2 | 194.09 | Irritant, harmful if excess swallowed. | salicylamide | C7H7NO2 | 137.14 | Irritant, harmful if excess swallowed. |
Table 1. Analgesics and respective chemical data Analgesic Name | Rf (cm) | UV color | Iodine stain | acetaminophen | 0.586 | - | orange | aspirin | 0.787 | blue | - | caffeine | 0.215 | - | - | salicylamide | 0.743 | blue | orange | Reference (1) | 0.297 | - | - | Reference (2) | 0.551 | - | orange | Reference(3) | 0.729 | blue | orang | Table 2. Observations of known
