Determination of magnesium and calcium in urine.

HE RENEWED INTEREST in magnesium alterations in human disease states has originated a search for simpler and more accurate analytic technics for the determination of magnesium in body fluids. Several recent methods are based upon the chelating reaction of ethylenediamine tetraacetic acid (EDTA). A procedure for the determination of magnesium in erythrocytes (1) involving spectrophotometric titration of the iron-free ifitrates of blood was developed in our laboratory by adaptation of one of these technics (2). The present paper deals with a new method for the determination of urinary magnesium and calcium using a technic that by overcoming the interference of inorganic phosphate allows the use of the reagents and titration procedure of the previous methods (1, 2), thus offering a very convenient uniformity of methodology for plasma, erythrocytes, and urine.