Measurement of total calcium in biological fluids: flame atomic absorption spectrometry

The measurement of total calcium (CaT) in biological fluids by flame atomic absorption spectroscopy (FAAS) is one of the more accurate yet practical methods available today. With attention to details at every analytical step, the imprecision of FAAS outlined above can be as low as +/- 0.01 mmol/liter at the 2.65 mmol/liter upper reference level of CaT found in the serum of healthy young adults (a CV of 0.4%). The accuracy of FAAS as judged by measurements of NBS/SRM #909, a lyophilized serum material carrying CaT values assigned by isotope dilution mass spectrometry, can be within +/- 1% (recovery of 99-101%) or less in skilled hands. As our brief section on application suggests, FAAS methods for CaT can be adopted to provide rapid and accurate results in many different biological fluids and tissues.