Dear Muhammad

If you are working with unknown sample, which is not validated prior to your studies, may have get higher activity then positive control. Although if you are working with known sample and reported by anyone prior to your study then their is need to re-validation of your activity with the reported results.

Many times it is possible due to personal error, experimental design and lab condition. So, try to perform your study by someone in other labs also. 

Thanks dear Mr Ali Abdil Razzaq Muhammed Noori Aldallal. It clarified my query.

Good day sir, thank you so much for your contribution sir, kindly forward me any of ur research article in which this method was used for the elution time and further studies. Thank you sir