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Ref. No. [UMCES] CBL 2015-011
ACT VS15-04
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As defined in the test protocols, two Metrohm electrodes were maintained within the test
tank throughout the lab study to provide a continuous, independent measure of pH at 15 minute
intervals. These results were not intended to be used as reference values for direct instrument
comparison, but because they were calibrated weekly with water from the test tank water against
the dye reference pH and they maintained their calibration in between intervals (Fig. 2; slope =
1.006, r
2
= 0.999), they provide a high resolution (15 minute) continuous time series of ambient
pH within the test tank. Therefore, Metrohm results are included within some of the time series
plots but no quantification of instrument accuracy was conducted with these data.
Figure 2.
Cross plot of matched Metrohm pH results that measured continuously within the test tank at
15 minute intervals versus dye measured reference pH results. Three-hundred, fifty-one dye based pH
measurements were made over the ten week test.