Methods for detecting one or more analytes, such as a protein, in a fluid path are described herein. In some embodiments a method includes resolving one or more analytes in a fluid path, such as, for example, a capillary. After the one or more analytes are resolved, the one or more analytes are bound to the fluid path upon activation of one or more triggerable agents disposed within the fluid path. The one or more analytes that are bound to the fluid path are detected within the fluid path.