Highly Sensitive Spectrophotometric and Spectrofluorometric Determinations of Albumin with 5,10,15,20-Tetrakis(4-sulfophenyl)porphine

Abstract

The 5,10,15,20-tetrakis(4-sulfophenyl) porphine (TPPS) has a highly sensitive absorption spectrum {Soret band: molar absorptivity (e) = 5.0x10⁵ M⁻¹ cm⁻¹ at 434 nm} and a red intense fluorescence. Moreover, it was determined that TPPS reacted rapidly with albumin at room temperature. The absorbance and the fluorescence intensity of TPPS were remarkably and quantitatively decreased by this reaction. Based on these facts, new spectrophotometric and spectrofluorometric determinations of serum albumin were developed. Each calibration curve was linear in the determination range of 0.1 ~ 9.0 μg/ml by spectrofluorometric determination and in the range of 0.2 ~ 6.0 μg/ml by spectrophotometric determination. The fluorometric detection limit was 0.05 μg/ml and the spectrophotometric one was 0.1 μg/ml. Further, the relative standard deviation (5 determinations) for 5 μg/ml albumin was 2.1 % (spectrofluorimetry) and 2.6% (spectrophotometry), respectively. When these methods were applied to the determination of albumin in dog spinal fluid, the results were satisfactory.