Search

A capillary optode for determination of mercury(II) in aqueous solution has been developed. The sensors are composed of the capillary glass tubes with a chemically sensitive coating on the inner surface, consisting of a 4-(2-thiazolylazo) resorcinol (TAR) and Nafion® composite thin film. When a sample solution is passed through a capillary tube, the mercury(II) ions forms complexes with the immobilised TAR resulting in a change of the colour of the inner surface of the capillary which, in turn, can be monitored spectrophotometrically. The characteristics of these sensors including effect of flow-rate and pH, reproducibility, sensitivity, linear range, life time and selectivity are discussed.

A simple optical flow injection ammonia sensor has been developed, based on the reflectance changes at 620 nm of an indicator fitted with a gas membrane. The sensor uses a commercially available pH indicator strip for a simple and fast assay. The response time to a 1-10 mM change in ammonia concentration is fast (≤10 seconds) and is fully reversible. The reversal time of the sensor is ≤30 seconds for ammonia assay and it can also be used for fast urea assay within the range 2-10 mM.

An optical fibre probe based on glucose dehydrogenase immobilized on nylon was constructed. The probe was used to quantitate glucose through a measurement of the fluorescence of the NADH formed by the enzyme-catalyzed reduction of glucose in the presence of NAD. The probe response was reproducible and displayed good linearity in the concentration range of 1.1 to 11.0 mM glucose. The limit of detection was 0.6 mM glucose. The response was affected by pH and NAD concentration.