Abstract: From 10 to >200 mg L-1 of protein has been determined in a flow injection apparatus with a detector cell containing a nickel oxide working electrode, a platinum counter-electrode and a SCE; the background electrolyte was 0.1 mM NiSO4 in 0.1 M NaOH, and amperometric measurements were made at 0.5 V. For denatured proteins, the detection limit was 1 mg l-1, and the technique has been used to study the denaturation kinetics of cytochrome c and serum albumin.

Abstract: The method is based on the agglutination, by protein, of calibrated latex particles coated with a specific antibody. The automated system consists of a modified sampler, a peristaltic pump, a thermostatic bath, a manifold, an optical cell counter equipped with a double-threshold system, and a recorder with a continuously adjustable scale. The reaction mixture (sample plus antibody-coated latex beads) is incubated in a heated mixing coil for 25 min, and the extent of agglutination is measured with the cell counter. No external shaking is required. A wide variety of proteins in plasma and urine, including human ferritin, β2-microglobulin, retinol-binding protein and albumin, have been determined. The detection limits range from 1 pM to 0.1 nM. Within- and between-assay coefficient of variation are <10%. In the assay of ferritin, sera are pre-treated to prevent interference from chylomicrons, complement and rheumatoid factor.