The
pH of drinking water is a vital measurement. If the pH is too low,
drinking water will be corrosive to the distribution system and water
pipes in homes. The pH of water also influences other properties
including taste, odor, clarity, and efficiency of disinfection. In the
United States, the pH of water is determined by a meter according to
EPA method 150.1 and Standard Methods 4500-H.
Measuring
pH of water low in minerals is difficult. The lower the mineral
content, the less conductive the water will be. Low conductivity water
presents a challenge since the pH meter is an electrochemical system
that relies on the solution being measured to be conductive.
Most
drinking water plants use either surface water (lakes, rivers, and
streams) or groundwater as their point source of water for treatment.
Surface water is typically lower in mineral content, resulting in
lower conductivity/TDS readings. Groundwater that has percolated
through limestone, dolomite, or gypsum, and generally has a higher
mineral content than surface water. However, there are sources of
groundwater that are also very low in mineral content.
The
HI99192 uses the FC2153 amplified pH electrode with glass body. This
specialized electrode offers numerous features that improve pH testing
in drinking water. An integrated temperature sensor allows for
temperature compensated pH measurements without the need for a
separate temperature probe. The probe’s spheric sensing tip has a wide
surface area for measurement in aqueous solutions.
An
integral part of any pH electrode is the reference junction. The
reference junction is a part of the electrode that allows for the flow
of ions located in the reference cell into the sample being measured.
The ions provide for an electrical connection between the reference
electrode and the indicating electrode. A standard pH electrode will
use a single ceramic junction that allows for 15 to 20 μL/hour of
electrolyte to flow.
The
FC2153 has three ceramic junctions providing for 40 to 50 μL/hour of
electrolyte to flow. This increased flow provides a greater continuity
between the reference electrode and the indicating electrode making it
suitable for water of low ionic strength. To optimize the flow from
the electrode the refill cap should be unscrewed so that it is open.
This allows for positive head pressure to be created allowing for the
electrolyte to flow more easily into the sample.
