Question

You are asked to determine the concentration of ions dissolved in water samples collected from a storm sewer. The client is only interested in the following anions: Cl–, Br–, NO3–, SO42– and the following cations: NH4+, Na+, K+, Ca2+ and Mg2+. For the scenario above, identify the best detection method for the analysis:

Question options:

FID

ECD

Refractive Index

UV Conductivity

TCD

Answer 1

For the scenario above the ideal method for detection of ion concentration is ECD. ECD is used to measure components displaying oxidation-reduction reactions, and detects electric currents generated by these reactions. The ECD has high selectivity, because the necessary voltage to cause an oxidation-reduction reaction depends on the component.

Here we are doing sensitivity analysis for an environmental contaminants in which the concentration of targeted components is low. Also we make use of the electrical activty present in the sample as it contains common inorganic anions and cations. Hence, ECD method is best suited for this senario.