1. MLAB 2401: Clinical Chemistry Keri Brophy-Martinez
Methods of Measurement:
Mineral and Bone Metabolism

2. Determination of Total Calcium
Colorimetric
O-cresolphthalein
Calcium in alkaline solution reacts with o-cresolphthalein complexone to form a purple complex
Proportional to the calcium concentration
Uses 8-quinolinol or 8-hydroxyquioline to remove Mg ions
Arsenzo III dye
Atomic Absorption Spectrophotometry
Reference method

3. Specimen Requirements: Calcium( total)
Serum
Lithium heparin plasma
Avoid the use of anticoagulants with EDTA or oxalate

4. Determination of Free Calcium
Ion selective electrodes used
pH dependent
Selectively and reversibly bind calcium ions
As calcium binds to the membrane a potential develops which is proportional to the concentration

5. Specimen Requirements: Calcium (Ionized)
Samples must be collected anaerobically
Heparinized whole blood preferred
Plasma
Serum

6. Reference Ranges Calcium, total Ionized Calcium 8.60-10.0 mg/dL

7. Determination of Phosphorus
Formation of ammonium phosphomolybdate complex
Complex measured by UV absorption at 340 nm or reduced to molybdenum blue and read between nm

8. Specimen Requirements: Phosphorus
Serum
Lithium heparin plasma
Avoid hemolysis and certain anticoagulants
Diural variation a factor

9. Reference Range: Phosphorus
mg/dL

10. Determination of Magnesium
Colorimetric
Calmagite
Mg2+ binds with calmagite to for a reddish-violet complex, read at 532 nm
Formazen dye
Mg2+ binds with the dye to form a colored product read at 660 nm
Methylthymol blue
Mg2+ binds with the chromogen to form a colored complex
Atomic Absorption Spectrophotometry
Reference method

11. Specimen Requirements: Magnesium
Serum
Heparinized plasma
Avoid hemolysis
Remove serum from cells ASAP

12. Reference Range: Magnesium
mg/dL

13. References
Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry: Techniques, principles, Correlations. Baltimore: Wolters Kluwer Lippincott Williams & Wilkins.
Sunheimer, R., & Graves, L. (2010). Clinical Laboratory Chemistry. Upper Saddle River: Pearson .