Biol. Pharm. Bull. 30(7) 1187—1190 (2007)

cells, proteins, and small molecules from the alveolar space of the lower respiratory tract since the first report of Reynolds and Newball over three decades ago. The analysis of these components is of wide diagnostic and investigative value. In bronchoalveolar lavage, sterile saline is administered into the bronchoalveolar space and aspirated by syringe. Because recovery of the components in bronchoalveolar lavage fluid (BALF) varies from sample to sample, their concentrations are usually normalized relative to those of albumin. Furthermore, the absolute concentration of albumin itself in BALF may allow characterization of interstitial lung disorders. Therefore a sensitive and simple method for determining trace amounts of albumin in BALF is desirable. Dye-binding methods are widely used for the determination of proteins, and spectrophotometric methods using bromocresol green are most commonly used in clinical assays of human serum albumin (HSA). However, the specificity for HSA in the bromocresol green method is not very high. The bromocresol purple method is also used in clinical measurement of HSA, and is more selective for HSA than the bromocresol green method. However, the bromocresol purple method is not applicable to BALF samples of low albumin concentration. Saito et al. reported a highly sensitive fluorimetric method using chromazurol S (CAS) for the determination of trace albumin, and pointed out that several reagents analogous to CAS including eriochrome cyanine R (ECR) are promising. Subsequently, Ci and Chen reported a fluorimetric method for the determination of HSA using ECR. They used 308 nm as the excitation wavelength. However, Saito’s group reported that the HSA-ECR complex showed visible excitation and emission spectra and low reagent blank at pH <4.0. Ultraviolet radiation may give rise to fluorescence of other components. Therefore in the present study we investigated the fluorimetric determination method of human albumin using ECR and visible range as excitation wavelength. This technique was applied to determine trace amounts of human albumin in BALF samples.