2.4. Coffee sample preparation
Raw coffee were ground and screened through 250 μm sieve to get a uniform texture. An accurately weighed amount of sieved coffee (approximately 50 mg) was dissolved in 25 ml of distilled water. The solution was stirred for one hour using magnetic stirrer and heated gently to remove caffeine easily from the solution. In addition the solution was filtered by a glass filter to get rid of particle from solution.