Analytical Sciences

Continuous in vivo Monitoring of Blood Diffusible Calcium Using On-line Microdialysis Sampling Coupled with Flame Atomic Absorption Spectrometry

Wei-Chang TSENG,* Yuh-Chang SUN,** Cheng-Fa LEE,*** Mo-Hsiung YANG,** and Yeou-Lih HUANG***

*Department of Medical Technology, Fooyin University, Kaohsiung, Taiwan
**Department of Nuclear Science, National Tsing-Hua University, Hsinchu, Taiwan
***Faculty of Biomedical Laboratory Science, Kaohsiung Medical University, Kaohsiung, Taiwan

A direct, rapid and continuous in vivo monitoring of diffusible calcium in the blood of living rabbits has been developed using microdialysis sampling coupled on-line with flame atomic absorption spectrometry. Microdialysates perfused through implanted microdialysis probes were collected with a sample loop on an injection valve and directly introduced into the flame atomizer by a carrier solution. An ultrapure saline solution (0.9% NaCl, pH 7.2) was used as the perfusion solution at a flow rate of 20 µl min^-1 via the microdialysis probe. A 0.1% La solution in 0.5% HNO₃ solution was employed as the carrier solution at a nebulizer uptake flow rate of 2.5 ml min^-1. The interval for each determination was 2.5 min (2 min of sampling time, 20 s of read time and 10 s of washing time). The performance characteristics of the on-line microdialysis-FAAS system were validated as follows: linearity range, 0 - 100 mg l^-1; detection limit (3 σ, n = 7), 3.66 mg l^-1; precision (RSD, n = 50), 6.2%. For the evaluation of analytical accuracy, the proposed on-line method was compared with the in vivo no net flux method. The use of an on-line microdialysis-FAAS system permitted the in situ, dynamic and continuous in vivo monitoring of diffusible calcium in the blood of the living rabbits after CaCl₂ administration with a temporal resolution of 2.5 min.

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