We assessed five quantitative methods for the determination of urinary total proteins, three of them with precipitation followed by spectrophotomollowed by spectrophotometry (Tsuchyga/Benedict, Tsuchyga/Biuret and TCA/Biuret); one with gel-filtration (Sephadex G50/Biuret) and a Turbidimetric procedure (SSA). 2. Day-to-day precision was between 3.58 %CV (Tsuchyga/Benedict) and 11.46 %CV (Sephadex/Biuret). The Tsuchyga/Benedict method showed the closest values to controls quantitated by the Kjeldahl method and the lowest detection limit )17.3 mg of total proteins per liter). Recovery studies showed that a level of 100-200 mg/l the Tsuchyga/Benedict recovered over the 96% of the protein added. 3. Comparison studies of 66 24-hour urine samples showed that the best correlation was obtained between the Tsuchyga/Benedict and the Tsuchyga/Biuret methods (r = 0.996). 4. We conclude that the Tsuchyga/Benedict is a sensitive, precise and accurate procedure for the routine quantitation of urinary total proteins.
