Total protein concentration in plasma samples is normally used as a parameter to control animal health and nutritional conditions. Normal concentration levels are in the range of 60 to 85 g L-1 total protein for animals of good development. The methods proposed for its determination generally present as a disadvantage an excessive handling during operation. In this work an automated flow procedure for total protein determination in bovine serum samples, employing the Biuret method, was developed. The system, including an automatic injector commutator and a three way solenoid valve computer controlled, was designed in order to permit on line sample dilution. Since protein standard solutions were introduced with and without dilution. A dilution factor was estimated and used to calculate protein concentration obtained after on-line dilution of the samples. Solutions samples were inserted through a three way solenoid valve that allows precise dilution minimizing hand operations. The analytical range for total protein determination was 2.5 to 20.0 g L-1, and considering the dilution employed, bovine plasma samples with 12.5 to 100.0 g L-1 of total protein were analysed. The procedure presented a 2.8% rsd and analytical frequency of 76 determinations per hour. Results were in good agreement with the traditional method (Biuret) and no significant difference was verified at 95%.
protein; on line dilution; flow system; blood plasma
