If students in undergraduate analytical chemistry education analyze samples of known composition, their results can be verified. If the students get a "real" sample with an unknown composition in the frame of a problem-posing approach to teaching, it is difficult to check whether the students work accurately or not. Thus it is advisable to apply at least two different analytical methods. In this way the students gain a better insight into the differences and similarities of the diverse analytical methods and, by comparing the analytical results obtained with these methods, they get a better idea of the possibilities and accuracies. An important advantage in this approach is that students stimulate themselves to repeat experiments if different values are obtained from different analytical methods. This approach is demonstrated by the determination of caffeine in coffee applying a UV spectrophotometer, HPLC equipment, and CE apparatus. Some representative results are given showing the accuracy of the methods and showing the differences between the separation methods HPLC and CE versus UV spectrophotometry.