Highly Selective Caffeine Coated-Wire Electrode Based on the Molecularly Imprinted Polymer

The molecular imprinted polymer (MIP) was synthesized by precipitation polymerization with caffeine as template, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. A selective electrode for the potentiometric determination of caffeine in the aqueous medium was developed using the MIP-modified coated-wire electrode. The electrode shows response for caffeine in a concentration range of 1.0×10-8 to 1.0×10-5 M with a lower detection limit of 5.0×10-9 M. The electrode can be used for more than 100 times. The response time is 15 s and the signal is constant in the pH range 6.4 to 9.0. The electrode can be successfully applied for the monitoring of caffeine in syrup sample.

Determination of Nd3+Ions in Solution Samples by a Coated Wire Ion-Selective Sensor

A new coated wire electrode (CWE) using 5-(methylsulfanyl)-3-phenyl-1H-1,2,4-triazole (MPT) as an ionophore has been developed as a neodymium ion-selective sensor. The sensor exhibits Nernstian response for the Nd3+ions in the concentration range of 1.0×10−6-1.0×10−2M with detection limit of 3.7×10−7M. It displays a Nernstian slope of 20.2±0.2 mV/decade in the pH range of 2.7–8.1. The proposed sensor also exhibits a fast response time of ∼5 s. The sensor revealed high selectivity with respect to all common alkali, alkaline earth, transition and heavy metal ions, including members of the lanthanide family other than Nd3+. The electrode was used as an indicator electrode in the potentiometric titration of Nd(III) ions with EDTA. The electrode was also employed for the determination of the Nd3+ions concentration in water solution samples.