Light scattering-based determination of fibrinogen in human plasma using an automated continuous system

A simple light scattering method for the determination of fibrinogen in plasma is presented. The method is based on the analyte precipitation in the presence of ammonium sulphate in glycine hydrochloride buffer. The approach is developed by using a simple flow injection manifold where the light scattered by the solid suspension formed is monitored in a conventional spectrofluorimeter with an incident wavelength of 340 nm. The optimized method provided a linear determination range between 1.0 × 10−3 and 2.0 × 10−2gl−1 of fibrinogen with a precision, expressed as rsd%, of ± 1.33 and ± 1.30 for fibrinogen concentrations of 5 × 10−3 and 1.2 × 10−2 gl−1, respectively. The fast kinetics of the precipitation reaction and simplicity of the method provided a high sampling frequency, estimated at 80 h−1. The method was applied to the determination of fibrinogen in 35 human plasma samples from healthy and sick individuals, after a 1:250 dilution with an acceptable correlationship with a standard nephelometric method and recoveries between 89% and 108%.