A comparison of reference method values for calcium, lithium and magnesium with method-dependent assigned values.
Commercially available control sera were analysed by the reference methods for calcium, lithium and magnesium. Calcium: The mean deviation of the target values for routine flame atomic absorption spectrometry from the reference method values was -1.2%, in the case of flame atomic emission spectrometry -0.1%. The assigned values of determinations by methylthymol blue and cresolphthalein showed a positive bias: +2.3 and +2.2%. Lithium: Target values for routine flame atomic absorption spectrometry and flame atomic emission spectrometry were in generally good agreement with the reference method values (deviation +1.7% and +0.7%), although the differences were dependent on concentration. Magnesium: The assigned values for routine flame atomic absorption spectrometry yielded a mean bias of -0.4% from the reference method value. The target values for absorption spectrometry after reaction with Magon and Calmagite, however, differed by +8.2% and +9.3% on average. These methods seem to be less suitable for the determination of magnesium in serum than FAAS and would have failed several times to meet the requirements of quality assessment.
Külpmann
W R
WR
Institut für Klinische Chemie I, Medizinische Hochschule Hannover.
Buchholz
R
R
Dyrssen
C
C
Ruschke
D
D
D002118:Calcium / Q000097:blood*; D002138:Calibration / Q000592:standards; D008094:Lithium / Q000097:blood*; D008274:Magnesium / Q000097:blood*; D012015:Reference Standards; D012016:Reference Values
D008094:Lithium; D008274:Magnesium; D002118:Calcium