Phan Na Yên

Hi all, I got stucked in my report of protein purification. My sample protein mixture (catalase + lysozyme in 5mM phosphate buffer, pH 7.5) is separated by DEAE-Sepharose chromatography. after separation, my fraction has enzyme activity was 217iu whereas crude sample is 135iu.That means %yield of enzyme > 100%. It doesn't make any sense 'cause %yield is supposed to be less than or equal to 100%, right? I'm quite sure that the whole experimental process there is no error or mistake at all. Does any one can suggest any solution for me in this case? Thank you so much!