This method allows the direct measurement of low levels of sodium without prior extraction procedures, which minimises possible sources of contamination.
The polyethylene bottles to be used for sample preparation are first soaked in 20% v/v HNO3 for 24 hours, rinsed with distilled-deionised water and dried in a clean atmosphere. Diluent Solution: 0.01% glycerol in 5% HNO3.
Preparation of sample
The cement sample is thoroughly ground and the powder is mixed to ensure a homogeneous sample is obtained.
Representative cement samples weighing from 1 to 30mg are placed in a 25ml polyethylene bottle and 10ml of the glycerol diluent is added to the bottle. The sample solution is then shaken for 30 minutes.
Standards are prepared in the glycerol stock solution from concentrated aqueous stock solutions.
To estimate the range of standards that should be used for analysis, the BWB Technologies Flame Photometer offers a single point calibration.
Preparation of Standard Graph
Set the flame photometer in accordance to MultiPoint/Single Ion Calibration found on page 24 of the BWB Technologies Installation and Operation Manual, to measure potassium emission. Nebulise the working standard solutions and adjust the controls until steady zero and maximum readings are obtained. Nebulise the intermediate working standard solutions and construct a graph relating raw emission data (known as RAW in BWB the flame photometer) to concentration of all the standard solutions.
1 Epstein, M.S. & Rush, T.A. ‘The Determination of Low Concentrations of Sodium in Cement by Flame Emission Spectrometry without Sample Preparation’, Appl. Spectroscopy, 45 (1991), p. 1568-1570.
2. U.S Naval Civil Engineering Laboratory (1964). Port Hume, California: US NAVY. 26.