Does ninhydrin staining detect triethylamine?

My reaction mixture has amine compounds, so it shows tailing in bare silica plates. Therefore I decided to add small amount of triethylamine in the eluent. Because my amine compound is not detected by UV, I used ninhydrin staining. But something went wrong. The whole plate turned purple. I tried spot only triethylamine in the plate, dipped into ninhydrin solution, and heated it. The purple color showed. What is the problem? Doesn't ninhydrin only detect the amines which have N-H bond? Searching for this problem, I found that staining with ninhydrin shortly after eluting with 1% triethylamine is one of rookie mistakes in TLC. But how can the ninhydrin detect triethylamine which is a tertiary amine?