Measurement of urinary chloride with the Kodak Ektachem 400.

Urinary chloride can be measured simply, precisely, and accurately with the Ektachem 400 clinical chemistry analyzer. Because the coated film technique used in this instrument requires the presence of a protein matrix, we added a protein-based calibrator to the urine samples to overcome the low protein concentration in these specimens. Its advantages over a coulometric titration method (Astra analyzer) include the extension of the range of linearity to lower concentrations and the absence of interference from prednisone metabolites in urine. A disadvantage is the negative bias interference of allopurinol.