Calcium Measurements in Serum and Plasma—Total and Ionized

Abstract

This article will review the methods currently employed for measuring the concentrations of total and ionized calcium in serum or plasma. As far as total calcium is concerned, various techniques such as atomic absorption spectrometry, spectrophotometry, fluorometry, complexometric titration, and flame photometry will be described and compared. Particular emphasis will be given to the accuracy and precision of each technique. Possible sources of error and interfering agents will be identified and the various procedures for the taking and handling of blood samples evaluated. Inter-laboratory variation in the measurement of calcium will be studied. An assessment will be made of a new reference method for measuring total calcium in serum using isotope-dilution mass spectrometry. The usefulness of the total calcium measurement in clinical medicine will be briefly discussed. Within the last decade the refinement of spectrophotometric techniques and the improvements in ion-selective electrode technology have revolutionized the measurement of ionized calcium in serum, such that it may now be possible to replace total calcium measurements with ionized calcium measurements on a routine basis. The various techniques currently in use for measuring ionized calcium will be described and evaluated. Particular attention will be paid to the preparation of standards, the procedures for taking blood samples, and the handling of the samples prior to and during measurement. An assessment of the relative value of measuring total and ionized calcium will be presented.

In Vitro Sustained Release of Calcium Ions and pH Maintenance from Different Vehicles Containing Calcium Hydroxide

“…To precisely assess the amount of calcium ion released, the accuracy of the adopted technique is of a great importance. Several methods like atomic absorption spectrometry, ultraviolet spectrophotometer, fluorometry, flame photometry, and complexometric titration with EDTA have been used (31). However, there is a lack of comparability between the results from these different methods used because of the variability of experimental conditions and materials tested.…”

Calcium Loss From Root Canal Dentin Following EDTA, EGTA, EDTAC, and Tetracycline-HCl Treatment With or Without Subsequent NaOCl Irrigation

“…Methods such as atomic absorption spectrometry, flame photometry, complexometric titration with EDTA, or inductively coupled plasma-atomic emission spectroscopy (ICP-AES) are all suitable measurement techniques, provided that calibration is accomplished precisely (14,(23)(24)(25). Flame photometry (also known as flame emission spectroscopy) is a highly sensitive atomic emission method for the detection of metal salts such as Ca 2ϩ and is used extensively for clinical, biologic, and environmental analysis (26)(27)(28).…”

Calcium Metabolism in Health and Disease

“…Serum calcium ranges from ϳ8.8 to 10.4 mg/dl (2.2 to 2.6 mM) in healthy subjects. It comprises free ions (ϳ51%), protein-bound complexes (ϳ40%), and ionic complexes (ϳ9%) (7). To avoid calcium toxicity, the concentration of serum ionized calcium is tightly maintained within a physiologic range of 4.4 to 5.4 mg/dl (1.10 to 1.35 mM).…”