Chloride measurement by microelectrode in cystic fibrosis and normal sweat

The Lazar Ultra-M chloride-specific microelectrode was evaluated in a series of experiments designed to assess its suitability for the routine determination of human sweat chloride concentrations. NaCl solutions were used to construct a standard curve, and same-day variations in experimental results were less than 1%, while day-to-day variation was also less than 1%. Human sweat collected following pilocarpine iontophoresis was used to compare the chloride concentration measured titrimetrically by a hospital laboratory or by liquid chromatography with the value measured by the microelectrode. There was excellent correlation between each of the methods (r = 0.97). No false positive results were reported in 55 patients whose sweat chloride concentrations ranged from 7 to 43 mmol/l and no false negative values were reported from 6 patients with elevated sweat chloride concentrations (60-124 mmol/l). These results indicate that this new chloride microelectrode offers a simple and reliable method for sweat chloride measurement.