Spectrophotometric determination of total proteins by derivatization with p-benzoquinone in a flow system

The determination of total proteins in plasma is largely needed in clinical and biochemical areas because it is important for the diagnosis of several diseases. This paper describes a flow method for determination of total protein in human serum albumin samples using p-benzoquinone (PBQ) dissolved in dimethyl-sulphoxide (DMSO) as reagent. The reactional mixture at pH 8.0 or 9.0 was pumped through a coiled stainless steel capillary tube reactor, heated at 90 degreesC, to a spectrophotometric flow cell where the absorbance was monitored at 361 nm. A linear dynamic range was observed for protein concentrations from 50 to 500 mug mL(-1). Results were in good agreement with those obtained by the Kjeldahl's method.