Yes, of course the Bradford reagent can expire and therefore it can become unstable, which influences its reaction with proteins and therefore it will influence the result of the real value of the proteins present in your sample.

Add to that, the Bradford reagent is photosensitive, it must always be kept in the dark.

Hello Nesrin Tarfaoui

Yes, it is important to check the expiry of Coomassie Brilliant Blue G250 for Bradford assay. If the dye is too old, it can cause the absorbance level of the standard to appear lower than its true value. If stored as indicated, the shelf life of Coomassie Brilliant Blue G 250 powder is 3 – 5 years. Please refer to the product information provided below.

https://www.serva.de/www_root/documents/17524_e_1.pdf

The Bradford reagent comprises of Coomassie Brilliant Blue G-250 dye, ethanol, and phosphoric acid.

The protocol to prepare Bradford reagent is as follows.

Dissolve 100 mg Coomassie Brilliant Blue G250 in 100 mL of 85 % (v/v) phosphoric acid and 50 mL 95 % (v/v) ethanol. After the dye is dissolved adjust the volume to 1 L with water. The reagent is stable for several months. If a precipitate forms, you may filter through the filter.

Best,

Yes, it is necessary to verify if Coomassie Brilliant Blue (CBB) has expired for the Bradford assay since outdated dye might produce incorrect results. Keeping it in a cold, dark environment helps to maintain its stability for at least 3-4 years. The suggested CBB G-250 concentration in the Bradford reagent is 0.01% (w/v). It is often blended with 85 % phosphoric acid, 95 % ethanol, and water to adjust the final volume. In the experiment, 1 mL of the reagent is generally combined with the protein sample in a 1:20 to 1:50 ratio, depending on the protein content.