I'm working on cationic gelatin and would like to measure the free primary amines using TNBS method as following. One milliliter of gelatin or cationized gelatin solution (0.50 mg/mL) in phosphate buffered saline (PBS, pH 7.4) was mixed with 1.0 ml sodium bicarbonate solution (4.0%) and 1.0 mL TNBS solution (0.10%). The mixture was kept at 40 C for 2 h protected from light and then the absorbance of the solution at 415 nm was determined. A calibration curve was prepared for b-alanine. The primary amino group content was expressed as the amount of TNBS-reactive amino groups in 1 g gelatin or cationized gelatin.

My question is about b-alanine calibration curve? how to make it?

Thank you