A method for determining the logarithmic reduction value of a LRV Size exclusion filter of a size exclusion filter G for a particle that is contained in a process solution and is to be filtered out in a filtration system, which comprises the size exclusion filter G and a process adsorber P, wherein the size exclusion filter G is protected from a blocking adsorbing species contained in the process solution by means of the process adsorber P that is connected in series upstream of the size exclusion filter and wherein the particle to be filtered out by means of the process adsorber P is retained with a LRV Process adsorber of 0.5 or more, comprising the steps: (a) providing a test system, comprising a size exclusion filter G, whose LRF Size exclusion filter is to be determined, and a test adsorber T connected upstream of the size exclusion filter G, which consists of a material similar to the process adsorber P and by means of which the particle to be filtered out is retained with a known LRV Test adsorber of 2 or less, wherein LRV Test adsorber < LRV Process adsorber; (b) determining LRV Test system of the test system for the particle to be filtered out in the process solution; and (c) calculating LRV Size exclusion filter by subtracting the LRV Test adsorber from LRV Test system, where LRV = log Cfeed Cfiltrate wherein c feed is the concentration of the particle to be filtered out in the process solution prior to passage of a filter and c filtrate is the concentration of the particle to be filtered out in the process solution after passage of the filter, and wherein the process adsorber P has a specific adsorption capacity k 1 for the blocking adsorbing species, is present on a scale M 1 and has a total adsorption capacity for the blocking adsorbing species of k 1 × M 1, and wherein the test adsorber T has a specific adsorption capacity k 2 for the blocking adsorbing species, is present on a scale M 2 and has a total adsorption capacity for the blocking adsorbing species of k 2 × M 2, and where 0,1 < k 1 M 1 k 2 M 2 < 10. wherein the size exclusion filter G is protected from a blocking adsorbing species contained in the process solution by means of the process adsorber P that is connected in series upstream of the size exclusion filter and wherein the particle to be filtered out by means of the process adsorber P is retained with a LRV Process adsorber of 0.5 or more, comprising the steps: (a) providing a test system, comprising a size exclusion filter G, whose LRF Size exclusion filter is to be determined, and a test adsorber T connected upstream of the size exclusion filter G, which consists of a material similar to the process adsorber P and by means of which the particle to be filtered out is retained with a known LRV Test adsorber of 2 or less, wherein LRV Test adsorber < LRV Process adsorber; (b) determining LRV Test system of the test system for the particle to be filtered out in the process solution; and (c) calculating LRV Size exclusion filter by subtracting the LRV Test adsorber from LRV Test system, (a) providing a test system, comprising a size exclusion filter G, whose LRF Size exclusion filter is to be determined, and a test adsorber T connected upstream of the size exclusion filter G, which consists of a material similar to the process adsorber P and by means of which the particle to be filtered out is retained with a known LRV Test adsorber of 2 or less, wherein LRV Test adsorber < LRV Process adsorber; (b) determining LRV Test system of the test system for the particle to be filtered out in the process solution; and (c) calculating LRV Size exclusion filter by subtracting the LRV Test adsorber from LRV Test system, where LRV = log Cfeed Cfiltrate wherein c feed is the concentration of the particle to be filtered out in the process solution prior to passage of a filter and c filtrate is the concentration of the particle to be filtered out in the process solution after passage of the filter, and wherein the process adsorber P has a specific adsorption capacity k 1 for the blocking adsorbing species, is present on a scale M 1 and has a total adsorption capacity for the blocking adsorbing species of k 1 × M 1, and wherein the test adsorber T has a specific adsorption capacity k 2 for the blocking adsorbing species, is present on a scale M 2 and has a total adsorption capacity for the blocking adsorbing species of k 2 × M 2, and where 0,1 < k 1 M 1 k 2 M 2 < 10.