Kinetic methods for the determination of cadmium(II) based on a flow-through bulk optode

Three kinetic methods based on flow injection, flow, and stopped-flow injection were applied for the determination of Cd(II) using a flow-through bulk optode membrane that incorporates 1-(2-pyridylazo)-2-naphtol (PAN) in a plasticized poly(vinyl) chloride membrane entrapped in a cellulose support. The calibration graphs plotting the reflectance at 560 nm versus [Cd(II)]1/2 for the first two methods and versus [Cd(II)] for the third were linear up to 56.2 mg l−1. The detection limits of the methods were 0.01, 0.06 and 0.8 mg l−1, respectively. The FI method was selected for application purposes. The variation coefficient of the sensor response for 11.2 mg l−1 of Cd(II) was ±0.31 and ±0.65% between different membranes. The sensor can be readily regenerated with a carrier (acetic–acetate) buffer of pH 4. The FI method was applied to the determination of cadmium in an alloy and in water.