title: Simultaneous flow injection determination of calcium and fluoride in natural and borehole water with conventional ion-selective electrodes in series.
abstract: An on-line automated system for the simultaneous flow injection determination of calcium and fluoride in natural and borehole water with conventional calcium-selective and fluoride-selective membrane electrodes as sensors in series is described. Samples (30 mul) are injected into a TISAB II (pH=5.50) carrier solution as an ionic strength adjustment buffer. The sample-buffer zone formed is first channeled to a fluoride-selective membrane electrode and then via the calcium-selective membrane electrode to the reference electrodes. The system is suitable for the simultaneous on-site monitoring of calcium (linear range 10(-5)-10(-2) mol l(-1) detection limit 1.94x10(-6) mol l(-1) recovery 99.22%, RSD<0.5%) and fluoride (linear range 10(-5)-10(-2) mol l(-1) detection limit 4.83x10(-6) mol l(-1) recovery 98.63%, RSD=0.3%) at a sampling rate of 60 samples h(-1).
authors.affiliation: Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa.
authors.forename: J F
authors.initials: JF
authors.lastname: van Staden
authors.forename: R I
authors.initials: RI
authors.lastname: Stefan