I ran a TSH sample using HBS P+ with 0.5M NaCL. Back in 6/15/11 I got some binding on the Capture level for the Ab. Then 8/15/11, I ran the same system and now I am getting an inverted curve. I wanted to make sure I did not grab the wrong diluent so I repeated the test ensuring that the same buffer for the assay is used in diluting the samples. It still showed an inverted peak. Any ideas on what maybe going wrong?
Here are sensorgrams of the the analysis..the flat line is the buffer. Top one was in 6-15. Bottom one was in 8-16. One thing did change though in-between these times is a new IFC was installed. But did not think this was going to make a difference.