As mentioned in my previous blog post, electroneutrality (E.N.) is a powerful tool to find errors in major ion analyses. Histograms are an efficient way of presenting and reviewing E.N. values. A histogram divides the active data into ranges and plots the number of points (i.e. samples) in each range.
AquaChem enables you to easily create a histogram of any parameter in your database with many options to help control the output display:
For E.N., most values should be within ±10% of zero. Values outside this range usually indicates missing anions or cations.
AquaChem lets you quickly identify which samples have questionable values by clicking on the histogram plot bars. For example, if you click on the bar closest to -100, as shown in the figure below, all samples that fall within that plot interval are highlighted within the sample list.
An alternative and quicker way of identifying samples with a bad ion balance is by querying for samples with E.N. >15% or E.N. < -15%.
Using AquaChem’s Find function, you can create simple or complex queries to locate specific samples, including samples that might have questionable E.N. values, as shown in the figure below.
Queries you design can be saved and used from within the sample Filter to view only those samples that meet the specified criteria. For such filtered selections, AquaChem always displays the count and percentage of samples that meet your filter criteria in the sample window header:
This is a good way to begin a sample quality assurance routine, to identify samples that might have questionable results for major ions.
Learn more or download a free trial of AquaChem water quality analysis and reporting software