Bromocresol purple dye-binding method for the estimation of serum albumin adapted to the SMA 12/60

We describe a method for the determination of serum albumin on the SMA 12/60 that utilizes the anionic dye bromocresol purple (BCP). This dye is more specific than the commonly used bromocresol green (BCG) in that it does not bind to globulins. The SMA module requires two simple changes for the BCP method to be adopted: a 600 nm interference filter replaces the 630 nm filter; and a gray-gray pump tube (rated at 1.00 mL/min) replaces a green-green tube (rated at 2.00 mL/min) in the predilution assembly. The precision of this method is comparable to the BCG method with a CV of 2.9% at mean values of 30.6 and 38.3 g/L. This method was compared to the BCP method of the DuPont aca using 51 patient samples over an approximate albumin range of 15 to 80 g/L. The correlation is very good as indicated in the linear regression data: (SMA) = 0.884(aca) + 3.46; coefficient of determination (r2) is 0.986; and standard error of the estimate (Sy.x) is 1.39 g/L. Neither hemoglobin nor bilirubin interferes with this BCP method up to levels of 9 g/L and 633 mumol/L, respectively.