The Introduction of Bromocresol Purple for the Determination of Serum Albumin on SMAC and ACA, and the Standardization Procedure

The bromocresol purple methods for the determination of serum albumin on the Technicon SMAC and the DuPont ACA systems were evaluated and compared with the corresponding bromocresol green methods, a radial immunodiffusion (RID) and an electrophoresis technique. The linearity and precision of the dye binding methods were comparable. The bromocresol purple methods were more influenced by lipaemia and to a lesser extent by high bilirubin concentrations. The specificity of the bromocresol purple methods was superior to that of the bromocresol green methods and showed excellent correlations with the radial immunodiffusion method: bromocresol purple: SMAC = 1.03 (RID) + 0.32; bromocresol purple: ACA = 1.00 (RID) + 1.27. The bromocresol purple methods intercorrelated better than the bromocresol green methods. Freeze-dried sera can be used for albumin standardization. Analysis of the albumin fractions of freeze-dried and liquid sera by high-performance liquid chromatography (HPLC) did not reveal significant differences in albumin polymerization. Purified albumin reacted, irrespective of the degree of polymerization, very differently in the dye-binding methods. The bromocresol purple methods showed an overestimation of purified albumin, the bromocresol green methods an underestimation. The reason for these differences is unclear. Non-human albumin reacted poorly with bromocresol purple in contrast with bromocresol green.