Environmental conditions such as temperature variations, freezing/thawing, shaking during transport, and long-term storage might lead the appearance of a precipitate or floccule in the antibody solution. This is not uncommon. The floccule is typically buffer salts precipitating out of solution or a small bit of protein aggregation. If gentle, repeated inversion of the vial does not remove the precipitate to your liking we recommend removing the floccule by either filtration or centrifugation.
For filtration we recommend using a sterile 0.2 μM luer lock syringe filter. For centrifugation we would recommend transferring the antibody solution to a sterile centrifuge tube (do not centrifuge in the provided cryo vial) and centrifuging at 10k rpm for 5 minutes. We would suggest filtration over centrifugation since centrifuging may allow the sample to warm up for a longer period than filtration, which can be done very quickly. Regardless of what method is chosen you should use sterile filters, syringes, tubes, etc. and work in a biological safety cabinet to ensure that the solution remains sterile.
Rest assured that the precipitate can be removed with these methods without significant protein loss. If you are concerned about loss after centrifugation or filtration you can check the protein concentration after centrifugation or filtration and compare it to the concentration on the supplied CoA.
We measure protein concentration via absorbance @280 nm using an extinction coefficient of 1.33. When determining the concentration of our products, we first mix 100 μL of the stock antibody solution with 1.9 mL of pH matched PBS (1:20 dilution). We then take the A280 reading (after the spec has been blanked against our pH matched PBS), multiply it by 20 (as this is our dilution factor) and then multiply by 0.75 (which is the result of 1/1.33). Please keep in mind that we always supply a bit more protein in the vial than what was purchased.