In this project optical properties of pure caffeine, i.e., time dependency of caffeine in coffeernpowder and solution kept under different conditions and temperatures were inyestigated. FOI'rnthe pure caffeine molar decadic absorption coefficient and transitional dipole moment wererncomputed and found to be (1095 Â± 37) m2 mol-I and (I .3 Â± 0.2).0-30 C m. Respectively inrnall the systems and temperatures caffeine in coffee was investigated , a decrease in caffeinernconcentration as a function of time was observed. For the solution both in closed and openrnstorage conditions the pseudo zero order kinetics was observed. The rate constant ofrndecomposition k" = 2.41667xI0-5 mol m-3 hr-I for closed system and kJ = 5.50417xI0-5rnmol m-3hr-1 for open system were determined. The linear regression coefficient values werernabove R = 0.99 in both cases. The half-life time of caffeine were 1177 hI' and 517 hI' for closedrnand open systems, respectively. In the contrary, for open powder system the kinetics obeyed thernexpected first order rate expression. For open powder coffee the monoexponential fits resultedrnin rate constant of decay at room temperature (23Â°C) and in ambient atmosphere is computedrnto be k" = 2.4xI0-4 111.-1 and half-life time of caffeine is 289 hI', which implies again chemicalrnreaction during half-life was fastest for powder form storage than other conditions. Reactionrnrate was faster, as expected, for storage at 23Â°C than 8Â°CrnKey words: Caffeine, Coffee, Spectrophotometer, Pseudo Zero-Order, Monoexponential fit