Both PBS pH7.2 – 7.4 and Sodium Bicarb buffer pH 9.6 are commonly used capture antibody diluent. Our lab hasn't validated their performance. If you prefer, please run a pilot test to validate their effect. We recommend using "Capture Antibody Diluent: 100 mL H2O, 0.5 g Na2HPO4", which is stated on our datasheet.