Three-Dimensional Calibration for Routine Analyses of Bromide and Nitrate Ions as Indicators of Groundwater Quality in Coastal Territories

Parrino Parrino,Palmisano Palmisano,Loddo Loddo,Camera-Roda Camera-Roda

doi:10.3390/ijerph16081419

Parrino Parrino, Palmisano Palmisano + Show 2 more

Open Access

https://doi.org/10.3390/ijerph16081419

Copy DOI

Abstract

Nitrate and bromide ions are generally considered indicators of anthropogenic pollution and seawater intrusion, respectively, in the groundwater of coastal territories. The analysis of these species is generally carried out with routine chromatographic analyses which generally afford partially merged or poorly resolved peaks. In the present paper a simple method for the correct evaluation of their concentration in water is reported. This method does not imply utilization of other instruments or technologies, only the mathematical elaboration of the data obtained from routine analysis of standard solutions containing the two species. Standard binary solutions of nitrate and bromide ions at different concentrations, ranging between 0.1 and 2 mM, were analyzed by means of ion chromatography. Splitting two partially merged chromatographic peaks and considering each resulting area as originating from a single species produces “measured” concentration values which differ from the nominal ones. Such a procedure generates errors (one per species) which can be written as a function of the above mentioned “measured” concentrations and which can be graphically represented by means of a surface in a three-dimensional (3D) space. In this way, “measured” concentrations of bromide and nitrate ions can be corrected by calculating the errors generated under the experimental conditions at which the chromatographic separation is performed. Notably, this is analogous with the two-dimensional (2D) calibration normally carried out for analytical purposes. Indeed, both methods allow estimation of the unknown concentration of species in solution by correlating the instrumental response with the concentration of standard solutions.

Highlights

The sustainable exploitation of water may be considered one of the greatest challenges of the current century [1]
The simultaneous determination of bromide and nitrate ions is of paramount importance in preliminary water quality tests in order to identify the source(s) of pollution of the soil and of groundwater
Routine analyses of nitrate and bromide ions are essential for evaluating the quality of groundwater and of the soil

Summary

Introduction

The sustainable exploitation of water may be considered one of the greatest challenges of the current century [1]. While the determination of the chloride concentration is generally straightforward, the determination of bromide ions presents analytical issues as discussed below For these reasons, the simultaneous determination of bromide and nitrate ions is of paramount importance in preliminary water quality tests in order to identify the source(s) of pollution of the soil and of groundwater. The ions are separated by means of an ion exchange column and detected through a conductivity detector This method allows exact quantification only when the resolution of the peaks is good, but the use of low-efficiency anion exchange columns may generate significant errors in figures deriving from analyses of real water matrices. Using high-efficiency ion exchanging columns and ultraviolet-visible (UV-vis) or conductivity detectors may solve the problem [37,38,39,40,41] These methods often suffer interference by high nitrate concentrations (>100 mg·L−1 ) [38]. The present method is simple and reliable and is based on a calibration procedure applied on mixtures of two components

Experimental

Results

Figures were obtained by

Three-dimensional

The been by Figure integrating the the dependence on of

Conclusions