Wasu kwayoyin suna ƙunshe da murfin don inganta siffofin bayyanar kwayoyin, siffofin toshewa da siffofin membrane a wasu lokuta, amma canje-canjen waɗannan kayan aiki (Excipient) na iya haifar da karya kwayoyin, karya gefen da cire murfin. Wadannan matsalolin suna da muhimmiyar tasiri a kan sakin abubuwan da ke aiki a cikin kwayoyin, musamman kwayoyin da aka rufe da kayan narkewa na hanji da saurin saki. Wannan gwajin yana amfani da shi don auna ƙarfin haɗi tsakanin rufi da surface na kwamfutar hannu.