A potentiometric rhodamine-B based membrane sensor for the selective determination of chromium ions in wastewater.
The construction and performance characteristics of a novel chromate ion-selective membrane sensor are described and used for determining chromium(III) and chromium(VI) ions. The sensor is based on the use of a rhodamine-B chromate ion-associate complex as an electroactive material in a poly(vinyl chloride) membrane plasticized with o-nitrophenyloctyl ether as a solvent mediator. In a phosphate buffer solution of pH 6 - 7, the sensor displays a stable, reproducible and linear potential response over the concentration range of 1 x 10(-1) - 5 x 10(-6) mol l(-1) with an anionic Nernstian slope of 30.8 +/- 0.5 mV decade(-1) and a detection limit of 1 x 10(-6) mol l(-1) Cr(VI). High selectivity for Cr(VI) is offered over many common anions (e.g., I-, Br-, Cl-, IO4-, CN-, acetate, oxalate, citrate, sulfate, phosphate, thiosulfate, selenite, nitrate) and cations (e.g., Ag+, Ca2+, Sr2+, Co2+, Ni2+, Cu2+, Mn2+, Fe2+, Zn2+, Cd2+, Al3+, Cr3+). The sensor is used for determining Cr(VI) and/or Cr(III) ions in separate or mixed solutions after the oxidation of Cr(III) into Cr(VI) with H2O2. As low as 0.2 microg ml(-1) of chromium is determined with a precision of +/-1.2%. The chromium contents of some wastewater samples were accurately assessed, and the results agreed fairly well with data obtained by atomic absorption spectrometry.
Hassan
Saad S M
SS
Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt. saadsmhassan@yahoo.com
El-Shahawi
M S
MS
Othman
A M
AM
Mosaad
M A
MA
D000465:Algorithms; D002138:Calibration; D002857:Chromium / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D008567:Membranes, Artificial; D011199:Potentiometry; D012235:Rhodamines / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000032:analysis*
D007202:Indicators and Reagents; D008567:Membranes, Artificial; D012235:Rhodamines; D014874:Water Pollutants, Chemical; D002857:Chromium; C029773:rhodamine B