Development of a new bulk optode membrane for the determination of mercury(II) Original Research Article

A new procedure for constructing an optical fibre reflectance sensor of the bulk optode membrane type is presented. The optode membrane consists of a plasticized poly(vinyl chloride) (PVC) membrane in which the ionophore is dissolved, entrapped in a cellulose support. The new optode with the metallochromic indicator, 1-(2-pyridylazo)-2-naphthol (PAN), was incorporated into a newly designed flow-through cell and the injection system was optimized for the determination of Hg(II) at 560 nm in the range 2–200 mg l−1 (10−5–10−3 M) with a detection limit of 0.11 mg l−1 Hg(II). The coefficients of variation of the sensor response for 10 and 40 mg l−1 of Hg(II) were ±2.57 and ±0.88%, respectively, and the CV between four membranes was ±3.5%. The sensor can readily be regenerated with the carrier, potassium bromide solution. The optode is fully reversible. The method was applied to the determination of mercury in an alloy for dental prosthesis and to the indirect determination of sulphite in aqueous solutions.