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Application Note

Determination of Low Concentrations of Sodium and Potassium in Water Samples.


Initially the BWB-Tech Flame Photometer was turned on and the flame ignited, then it was left for 45 minutes to come up to temperature to increase the stability of the instrumentation. A series of standards were formed from a 10ppm stock solution of Sodium and Potassium ranging from a blank at 0ppm to 0.10ppm in 0.02ppm aliquots was formed. This was done via diluting 0.2ml of 10ppm sodium solution and 0.2ml of 10ppm potassium solution into a 100ml volumetric flask with Deionised water which formed a 0.02ppm standard, 0.4ml of the 10ppm stock solution was diluted in the same manner that formed a 0.04ppm standard etc till 1ml of 10ppm stock solution was used in the 5 th standard which formed a 0.1ppm stock solution. A blank solution of DI water was also prepared.

These standards were then aspirated into the flame photometer from lowest to highest concentration in multi-ion/multi point calibration mode. The instrument was then set to read mode and the sample was aspirated.


If the results of this analysis were unstable due to the low concentrations of Sodium and Potassium, diluting both the sample and standards with up to 20% xylene could theoretically increase the signal produced by increasing the temperature of the flame. This would have to be accounted for in the final result that was acquired from the analysis as the concentration of the water was diluted by 20% and may push the samples past the limit of detection for the BWB-Tech Flame photometer. Some inhouse experimentation with finding the perfect ratio of water sample to xylene added for a better result was recommended.

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