Electrophoretic stacking for sensitive determination of antibiotic ceftazidime in human blood and microdialysates from diabetic foot

An electrophoretic stacking method has been developed for monitoring the therapeutic level of the antibiotic ceftazidime in blood plasma and microdialysates taken from peripheral soft tissues of the lower limbs of patients with diabetic foot syndrome. The biological samples are treated by addition of acetonitrile in an amount of 75% v/v and injected into a capillary in a large volume; after turning on the separation voltage, the residual acetonitrile is forced out of the capillary by the application of hydrodynamic pressure. The clinical samples were separated in an optimised background electrolyte composed of 50 mM chloroacetic acid +20% v/v methanol +0.5% v/v INST coating solution. The attained LOD for ceftazidime equalled 0.42 μg mL⁻¹ (0.8 μM) and the migration time equalled 3.75 min when using a 25 μm capillary with minimum length of 31.5 cm. The separation was controlled by a maximum voltage of +30 kV and the movement of the analyte was accelerated by a pressure of 50 mbar. The RSD values for intra-day repeatability of the migration time and peak area are 0.14% and 3.8%, respectively; the inter-day values equalled 0.25% for the migration time and 7.3% for peak area, respectively. Pharmacological studies revealed that ceftazidime passes from the blood circulation to the peripheral tissues of the lower limbs with an efficiency of 20%. The introduction of CE control of ceftazidime level in diabetic foot represents a very important improvement in achieving the targeted therapeutic effect.