Fig. 7. ELISA calibration function for DCF with increasing concentration of different salts ((A) ■ 0 g L⁻¹ NaCl, 5.8 g L⁻¹ NaCl, 10 g L⁻¹ NaCl, 20 g L⁻¹ NaCl, 30 g L⁻¹ NaCl; (B) ■ 0 mg L⁻¹ CaCl₂, 50 mg L⁻¹ CaCl₂, 75 mg L⁻¹ CaCl₂).