On-line microdialysis sampling coupled with flame atomic absorption spectrometry for continuous in vivo monitoring of diffusible magnesium in the blood of living animals

A novel on-line microdialysis sampling coupled with flame atomic absorption spectrometry (FAAS) with an attractive application is reported. Microdialysates perfused through implanted microdialysis probes were directly introduced into the flame atomizer of a FAAS system using 0.2% HNO₃ as carrier solution at a nebulizer uptake flow rate of 6 ml min⁻¹. The interval for each determination was 90 s (60 s sampling time, 10 s read time and 20 s washing time). The analytical characteristics of the on-line microdialysis-FAAS system were validated as follows: linearity range, 0-300 mg l⁻¹; detection limit (3σ, n = 7), 0.53 mg l⁻¹; precision (R.S.D., n = 50), 4.1%. By comparing Mg levels in the blood of living rabbits with the results obtained from in vivo no net flux (NNF) method, the accuracy of the proposed on-line method was found to be good. The present method can be successfully applied to the in vivo monitoring of diffusible Mg in the blood of living rabbits after magnesium sulfate (MgSO₄) administration with a temporal resolution of 1.5 min.