Rl. Zhang et al., QUANTITATIVE-DETERMINATION OF IONIZED CALCIUM AND TOTAL CALCIUM IN HUMAN SERUM BY CAPILLARY ZONE ELECTROPHORESIS WITH INDIRECT PHOTOMETRIC DETECTION, The Journal of microcolumn separations, 6(3), 1994, pp. 217-221
We have developed a new method to quantitatively determine ionized cal
cium and total calcium by using high performance capillary electrophor
esis (HPCE) with indirect photometric detection. Other cations such as
Na+, K+, and Mg+ can also be quantitatively determined. A 70 cm x 50
mum i.d. fused silica capillary was used for the separation. The detec
tion window was located 25 cm from the cathodic end, and the detection
wavelength was set at 214 nm. A 100 mM imidazole solution at pH 7.4 (
adjusted with 5 % H2SO4) containing 0.1 % hydroxypropylmethylcellulose
(HMC, 4000 centipoise) was used as background electrolyte. Whole seru
m was injected for 5 s at 15 kV for the determination of ionized calci
um. The total calcium levels in a number of human serum samples were d
etermined by HPCE and compared with the NIST reference method (atomic
absorption), and the results agree with each other within 95 % confide
nce. Two NIST standards were analyzed by HPCE, and the results fit eac
h other perfectly. The ionized calcium levels in sera by this HPCE met
hod have been compared with those obtained with ion-selective electrod
e (ISE) method, and the results were lower than those of ISE, which wa
s what we anticipated. The effects of sample temperature and buffer pH
were studied.