In-situ reagent for detection of proteins

A protein and/or amino acid detecting composition comprising:

• (a) about 0. 1 mmol/L to about 10 mmol/L or phthaldiaidenyde,
• (b) about 1 mmol/L to about 20 mmol/L of a C3-C6 thiol selected from the group consisting of N-Acetyl-L-Cysteine (NAC), N-acetyl-D-peniciliamine, N-acetyl-cysteamine, N-acetyl-homocysteine, and rnercaptosuccinic acid,
• (c) about 10 mmol/L to about 100 mmol/L of a buffer with a pH in the range of from about 7.5 to about 10, and
• (d) about 0.01% v/v to about 2% v/v of a surfactant, wherein the composition further comprises
• (e) about 0.05 mmol/L to about 5 mmol/L of a thiol reducing compound selected from Dithiothreitol, 2-mercaptoethylamine, and Tris (2-carboxyethyl) phosphine;
• wherein the composition is stable at 4° C. for 6 months and 3 months at room temperature.