Langues

(UNESCO / Japan Young Researchers' fellowships programme)

Preparation and Characterization of Ion-selective Electrodes for the Determination of Some Water Pollutants in Groundwater

Summary of research carried out: 
Preparation and Characterization of Ion-selective Electrodes for the Determination of Some Water Pollutants in Groundwater

In this work we prepared new ion selective electrodes to determine copper (II) and mercury (II) pollutants in groundwater samples.

Determination of trace amounts of copper(II) in water samples by means of a new chemically modified carbon paste electrode based on 2,3;13,14-dibenzo-4,12-dioxo-1,15-dithia- 5,8,11-triazacyclopentadecane (DDTP). In this work, a new chemically modified carbon paste electrode (CMCPE) based on 2,3;13,14-dibenzo-4,12-dioxo-1,15-dithia- 5,8,11-triazacyclopentadecane (DDTP) has been developed to determine Cu2+ in water samples. The performance of this electrode was investigated using potentiometric measurements. The sensor developed shows a good linear response of 30.2 ± 0.8 mV per decade over the concentration range of 2.1 x 10-7- 1.0 x 10-2 M. It has a very low limit of detection, 3.5 x 10-8 M (2.21 ppb), with a response time of less than 10 s. The proposed electrode revealed very good selectivities with respect to alkali, alkaline earth and some transition metal ions. The results obtained from this study reveal that a potentiometric Cu-CMCPE based on 2,3;13,14-dibenzo-4,12-dioxo-1,15-dithia- 5,8,11-triazacyclopentadecane (DDTP) is an excellent Cu2+ selective sensor and can be used to determine this ion in the presence of considerable concentrations of common interfering ions. Applicable pH range, lower detection limit and potentiometric selectivity coefficients of the proposed sensor make it superior to other methods used for this purpose.

Potentiometric determination of low levels of Hg (II) in water samples by means of a new sensor based on salophen. A synthesized N,N-bis(salicylidene)-ophenylenediaminate (salophen) was used as an ionophore for the preparation of a new mercury ion-selective electrode. The electrode exhibits a Nernstian response over the concentration range of 1.0_10-7–5.0_ 10-4 M, with a slope of 57.3±0.5mV per decade of concentration. The limit of detection, as determined by the intersection of the extrapolated linear segments of the calibration plot, is 7.6_10_8 M. The electrode shows good selectivity towards Hg (II) with respect to many common anions. The response time of the sensor is extremely fast (≤ 2 mint) and can be used in the pH range of 3.0–7.8. The electrode was used to determine mercury in tap, mineral and groundwater samples.

In this work, we have discussed the application of salophen as a new ionophore for the detection of Hg (II) ions. The sensor responds to Hg (II) ions. The recognition of small molecules in binding with heavy metals has gained importance in the field of research. The newly synthesised diamine with two donating nitrogen atoms, low molecular weight and flexible structure was expected to act as a suitable ionophore in the preparation of carbon paste sensors for mercury ions of proper size and charge. To evaluate the analytical applicability of the proposed method, the sensor was used to determine mercury (II) in tap, mineral and groundwater samples.

 

28 May 2008