Fig. 1. (a) Isochratic analysis of a suite of eight common anions on an underivitized MPIC analytical column. Eluent: 15 mM KOH; Anions: 2 mg/L F⁻, 4 mg/L Cl⁻, 10 mg/L Br⁻, 10 mg/L I⁻, 10 mg/L SO₄²⁻, 10 mg/L NO₃⁻, 10 mg/L HPO₄²⁻ and 10 mg/L ClO₄⁻; (b). Isochratic analysis of a suite of eight common anions on an MPIC analytical column using a 4 mm ASRS Ultra suppressor in external water mode. Eluent: 2.5 M 18-crown-6 and 15 mM KOH. Anions: 2 mg/L F⁻, 4 mg/L Cl⁻, 10 mg/L Br⁻, 10 mg/L I⁻, 10 mg/L SO₄²⁻, 10 mg/L NO₃⁻, 10 mg/L HPO₄²⁻ and 10 mg/L ClO₄⁻. Injection: 25 μL injection loop, flow rate: 1.0 mL/min, temperature: 20 °C, suppressor: a 4 mm ASRS Ultra suppressor in external water mode.

Fig. 2. Optimal eluent concentration for perchlorate analysis. Isochratic analysis of a suite of eight common anions on an 18-crown-6 adsorbed MPIC analytical column using a 4 mm ASRS Ultra suppressor in external water mode. Eluent: 0.5 M 18-crown-6 and 5 mM KOH. Anions: 2 mg/L F⁻, 4 mg/L Cl⁻, 10 mg/L Br⁻, 10 mg/L I⁻, 10 mg/L SO₄²⁻, 10 mg/L NO₃⁻, 10 mg/L HPO₄²⁻ and 10 mg/L ClO₄⁻. Injection: 25 μL injection loop, flow rate: 1.0 mL/min, temperature: 20 °C.

Fig. 3. Optimal system configuration using AG4 guard column as the concentrator column. Five milliliters of Milli-Q water spiked with ClO₄⁻ was loaded onto the concentrator column at varying concentrations of perchlorate. Eluent: 0.5 M 18-crown-6 and 5 mM KOH. Injection: 5 mL loaded onto concentrator column, flow rate: 1.0 mL/min, temperature: 20 °C.

Fig. 4. Chromatogram of Idaho Falls, ID water sample spiked with varying amounts of perchlorate. Eluent: 0.5 M 18-crown-6 and 5 mM KOH. Injection: 5 mL loaded onto AG4 concentrator column, flow rate: 1.0 mL/min, temperature: 20 °C.

Fig. 5. Retention of perchlorate on Cryptand C1 concentrator column depending on the volume of sample injected (four volumes: 1.6, 2.5, 3.3, 5 mL). Sample:1 mg/L perchlorate, 1000 mg/L each Cl⁻, SO₄²⁻, CO₃²⁻. Columns: Cryptand C1 in injection loop (no separator). Eluent: 0.5 M 18-crown-6 and 5 mM KOH. Flow rate: 1.0 mL/min, temperature: 20 °C. One milliliter aliquots were collected and analyzed for total common anions (TDS) and for perchlorate on an AS11 Column with 10 mM NaOH eluent. Peak areas for common anions (Cl⁻, SO₄²⁻, CO₃²⁻) were combined and plotted together, on left. The peak areas for perchlorate are plotted separately.

Fig. 6. Optimal system configuration for high salt samples using Cryptand C1 as the concentrator column. 1.6 mL of high salt sample (1000 mg/L Cl⁻, SO₄²⁻, CO₃²⁻) spiked with varying concentrations of ClO₄⁻ was loaded onto concentrator column. The concentrator column was then washed with 0.5 mL of eluent and switched in-line with the MPIC analytical column. Eluent: 0.5 M 18-crown-6 and 5 mM KOH. Injection: 1.6 mL loaded onto concentrator column, flow rate: 1.0 mL/min, temperature: 20 °C.

Common anion content in drinking water from various cities^a