K. Yoshimoto et al., Visual determination of protein in urine using Bromochlorophenol Blue and a membrane filter, BUNSEKI KAG, 49(6), 2000, pp. 363-367
A visual method has been established for the determination of the urinary p
rotein concentration with Bromochlorophenol Blue (BCPB) and a membrane filt
er (MF). The acid-dissociation constant of HBCPB- is pK(a) (OH) = 4.2. At p
H 3.0, ternary association occurs between HBCPB-, BCPB2- and protein in sol
ution. After the associate is extracted onto a MF, HBCPB- in the associate
undergoes a significant color change from yellow to blue upon drying. Free
HBCPB- is not extracted onto a MF. The high extractability of the ternary a
ssociate and the significant color change provide a sensitive visual method
for protein detection. This method can be used to detect human serum album
in in urine visually at concentrations as low as 40 mg/l. There was good ag
reement between the results obtained for urinary protein by this method and
those obtained by the conventional Coomassie Brilliant Blue spectrophotome
try. The method reported here can be-used as a screening test for low, but
increased, protein in urine.