THE MICROCOLORIMETRIC DETERMINATION OF INORGANIC PHOSPHATE IN PLASMA AND URINE: I. QUANTITATIVE INVESTIGATION OF PRESENT COMMON PROCEDURES II. A SENSITIVE AND STABLE METHOD FOR PLASMA, SERUM, AND URINE

Abstract

A quantitative investigation of the common colorimetric procedures used for determining inorganic, phosphate was made to determine the factors affecting the sensitivity and color stability. A method is presented that is accurate to within ± 2% and is sufficiently sensitive to give quantitative color development with less than 1 γ of phosphorus. The color produced is quite stable for colorimetry. The method has been adapted to the determination of phosphorus in 0.1 or 0.02 ml. of plasma, serum, or urine or in the protein-free filtrate residue from the determination of sodium, potassium, calcium, and chloride in 0.4 ml. of plasma.