Reactivities of calcium and magnesium ions in measurement of specific gravity of urine with a test strip

Abstract

The effects of calcium and magnesium ions on the measurement of the specific gravity of urine with a test strip were investigated. Both ions gave significantly higher values than NaCl. The salts of calcium and magnesium indicate the characteristic that both ions lower the pHs of the citrate buffer, phosphate buffer and EDTA2Na solution. From this result, it can be interpreted that calcium and magnesium ions react with substances contained in the detection system to liberate hydrogen ions, resulting in a false positivity.