The Analysis of Small Ions With Physiological Implications Using Capillary Electrophoresis With Contactless Conductivity Detection

Simultaneous electrophoretic separation of inorganic anions and cations from ground waters by dual opposite end injection and their capacitively coupled contactless conductometric detection is described. The chemometry assisted method development revealed that using this type of detection, apart from many advantages, implies a careful fine tuning of experimental variables. Proper choice of buffer components is the most critical aspect of the recorded signal's quality and the obtained resolution, where minor changes could lead to major changes in the recorded electropherograms. From a big variety of acidic and basic electrolytes, a pyromellitic acid/citric acid based buffer (pH = 3.70) was chosen for the baseline separation of 11 cations and anions in a single, less than 3 min run, using a PVA coated fused silica capillary. The estimated limits of detection (0.07–2 ppm) and defined limits of quantification (0.3–7 ppm) were comparable or better than those described for indirect UV detection, allowing much broader linear ranges (up to 120 ppm) for most of the studied ions. Following method validation the method was successfully applied for the assessment of inorganic ion content of 51 geotagged drinking water (domestic well) samples collected from the rural area of Cluj County, Romania, and correlations between sample composition and their geographical origin were identified by multivariate data analysis.