Abstract: A gel filtration standard suitable for use as molecular weight markers for gel filtration chromatography for a mobile phase with denaturant. In one embodiment, the gel filtration standard comprises ovalbumin, myoglobin, and vitamin B12. In another embodiment, the gel filtration standard comprises phosphorylase b, ovalbumin, and myoglobin along with a reducing agent, such as, for example, dithiothreitol to reduce the multiple peaks of phosphorylase b to a single peak. In a third embodiment, the gel filtration standard comprises phosphorylase b, ovalbumin, myoglobin, and vitamin B12. The benefits of the gel filtration standards described herein include acceptable resolution values and usefulness in system suitability testing. The combination of markers can be used in day-to-day testing for system suitability in the denatured condition for GPC-HPLC analysis for many proteins.