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.
Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt. saadsmhassan@yahoo.com
Saad S M
SS
Hassan
M S
MS
El-Shahawi
A M
AM
Othman
M A
MA
Mosaad
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