Biuret Assay

Reagent
per liter final volome
6g sodium potassium tartrate (NaKC4H4O6.4H2O)(f.w. 282.22)
1.5g copper sulfate (CuSO4.5H2O)(f.w.249.68)
all dissolved(500ml) in order in 30g/300ml NaOH(f.w. 40.0) before bringing to fianl volume.
Discard if a black precipitate forms.

Assay
1. Warm up the spectrophotometer 10 min. before use.
2. Prepare standards from bovine serim albumin (BSA).
3. Using 4ml biuret reagent to 1 ml sample a recommended range is 0.5 to 20 mg protein.(If possible, dilute unknowns to an estimated 1 to 10 mg/ml with buffer.)
4. Use 1ml sample per assay tube and add 4ml Biuret reagen to each tube, vortex immediately.
5. let stand 20 min.
6. Read at 540nm.

BSA 10mg/ml standard curve exsample
1(0.049),2(0.097),4(0.186),8(0.374),10(0.459) with rigor buffer.