Determination of in-gel protein concentration by a ninhydrin-based method

Until now quantification of proteins in gel-based methods relies on the amount of protein loaded onto the gel. This does not, however, represent the amount of proteins in the gel and therefore determination of proteins within the gel is mandatory. A method to quantify proteins, both hydrophilic and hydrophobic, using in-gel digestion with proteases, subsequent acid hydrolysis and the use of the ninhydrin reaction is herein presented.