Patent ID: 7169562

Claim:
A process for detecting or determining a C-peptide containing impurity comprising human C-peptide, monkey C-peptide, or a mixture thereof, in a sample of recombinantly produced human insulin or a derivative thereof, by a non-radioactive assay, comprising the steps of: (a) adding a C-peptide tracer to the sample; (b) adding antibody specific for the C-peptide containing impurity to the sample, said antibody being capable of recognizing human C-peptide and monkey C-peptide; (c) adding a C-peptide second antibody bead capable of capturing said antibody specific for the C-peptide containing impurity to the sample; and (d) detecting or determining the presence of the C-peptide-containing impurity in the sample, wherein the process is performed at a pH of about 8.5 to about 9.0.