Determination of Hexavalent Chromium (Cr(VI)) Concentrations via Ion Chromatography and UV-Vis Spectrophotometry in Samples Collected from Nacogdoches Wastewater Treatment Plant, East Texas (USA)

Table 2

Concentration of Cr(VI) in the four treatment stages measured by ion chromatography (Dionex ICS 2100 with column: Dionex IonPac CS5A, 4 × 250 mm; guard column: Dionex IonPac CG5A, 4 × 50 mm; eluent flow rate: 0.36 mL/min; injection volume: 1000 µL; temperature: 30°C; back pressure: 1700–2000 psi; postcolumn reagent system conditions: flow rate: 0.12 mL/min; detection: visible absorbance, 530 nm; noise: 6–8 µAU; runtime: 10 min).

Treatment stages	Cr(VI) concentration, ppm; (mean ± standard deviation, )	% RSD
Aeration chamber	0.0019 ± 0.0020	105
Clarifier	0.0006 ± 0.0002	33.3
Chlorination chamber	0.0011 ± 0.0006	54.5
Sulfur dioxide chamber	0.0010 ± 0.0006	60.0