KCl as well as the Pierce columns showed reduced recovery at the lower starting concentration. In 0.5 M KCl, sample loss is more severe at lower protein concentration. As seen in Fig. 3, the
0.1 g/L test solutions yield below 5% recovery (corresponding to the limit of quantitation for the BCA assay). Similarly, the Pierce cartridges also yield below 5% recovery for the lower concentration test solutions. A 0.1 g/L sample would fall below the manufacturer’s recommended level for use with the Pierce cartridge. Interestingly, those methods with the poorest SDS depletion efficiency (KCl, TCA, Pierce detergent removal from intact proteins), also demonstrated the lowest protein recovery. These methods all incorporate protein- level purification, which is generally more susceptible to sample loss owing to the varied solubility of intact proteins relative to peptides.