Simultaneous Analysis of Anions and Cations in Drinking Water by CE-C4D

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Revision as of 19:42, 26 August 2013 by Oliver (Talk | contribs) (Working conditions)

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The successful application of C4D detection (eDAQ) by capillary electrophoresis for the monitoring and quantification of ten inorganic ions commonly found in drinking waters (ammonium, potassium, sodium, calcium, magnesium, lithium, chloride, nitrate, sulfate and nitrite) is described [1].

Introduction

The C4D from eDAQ was used in conjunction with an Agilent G1600 capillary electrophoresis system. Design of experiments (DoE) was employed as an extensive and fast approach for method optimization (highest selectivity and sensitivity within the shortest analysis time), and as a result the studied ions were baseline separated in less then 3 minutes. The optimized analytical method was validated in terms of specificity, linearity, precision, accuracy and limits of detection and quantification. Furthermore, the method was successfully applied for the assessment of inorganic ion content of 51 geotagged drinking water (domestic well) samples and correlations between sample composition and their geographical origin were identified by multivariate data analysis.

Equipment Required

Working conditions

  • Known sample: aqueous solution containing 15 ppm ammonium carbonate, 15 ppm potassium nitrate, 15 ppm calcium chloride, 10 ppm magnesium chloride, 10 ppm lithium sulfate, 15 ppm sodium nitrite
  • Buffer: 15 mM pyromellitic acid, 10 mM citric acid, 2 mM 18-crown-6 ether adjusted at a pH of 3.70 with histidine
  • CE Instrument:
    • Separation voltage +30 kV
    • Capillary: PVA coated fused silica capillary
    • Total length 60 cm, effective length 18 cm
    • Outer diameter 360 μm, internal diameter 50 μm
  • Sample injection: hydrodynamic, dual opposite end injection; First the sample was injected at the inlet applying a pressure of 500 mbar, followed by the second injection at the outlet, applying a negative pressure of 50 mbar for 5 seconds at the inlet
  • C4D settings: frequency 1000 kHz; amplitude 100%; headstage gain: ON
  • Data recording: low-pass filter: 5 Hz; range: 50 mV; sampling rate: 1000 data points per second with the aid of Chart v.5.5.8 software

Limits of Detection and Quantification

Ion NH4+ K+ Na+ Li+ Cl- NO3- NO2- SO42- Mg2+ Ca2+
LODc (mg/L) 1.54 0.45 0.075 0.094 2.51 0.92 0.076 0.901 0.44 2.33
LOQc (mg/L) 4.67 1.39 0.22 0.28 7.62 2.80 0.23 2.73 1.33 7.08



Reference: [1] Ioan Ovidiu Neaga, Bogdan Cezar Iacob, Ede Bodoki, The analysis of small ions with physiological implications using capillary electrophoresis with contactless conductivity detection, Journal of Liquid Chromatography & Related Technologies, accepted manuscript in 11th July 2013