Standardization of the Coomassie Blue method for cerebrospinal fluid proteins

Coomassie Brilliant Blue G-250 can be used to quantitatively determine proteins in cerebrospinal fluid. When the dye combines with protein, the absorption maximum of the dye shifts. The dye-protein color forms almost instantaneously and is stable for at least 1 h. The procedure is also insensitive to changes in temperature in the range of 20--30 degrees C. The absorptivities of the dye complexes with human albumin or globulin differ, thus a pure albumin or pure globulin standard is unsuitable; a standard containing 70% albumin and 30% globulins is the most appropriate for this application. A bichromatic approach to standardization increases the range of linearity of a calibration curve. The method gives values that are about 9% higher than a sodium sulfate-sulfosalicylic turbidimetric procedure for cerbrospinal fluid proteins.