500 795/Rev D/07-14
Page 29
3.1.1 Sodium
a
500ml volumetric flask. Fill to the mark with pure deionised water. To prepare the standard solution for use
with the flame photometer, this stock solution should be diluted 1 in 50.
Calculation:
Atomic weight Na = 23.0
Molecular weight NaCl = 58.46
Therefore, 0.634g NaCl contains
0.634 x 23 = 0.25g Na
58.46
Thus in 500ml of solution there is 250mg Na or 50mg Na/100ml.
Diluting 1 in 50 gives a standard of 1mg Na/100ml = 10ppm Na.
3.1.2 Potassium
y KCl, dissolve in pure deionised water and wash into a 500ml
volumetric flask. Fill to the mark with pure deionised water. To prepare the standard solution for use with
the flame photometer, this stock solution should be diluted 1 in 50.
Calculation:
Atomic weight K = 39.1
Molecular weight KCl = 74.56
Therefore, 0.477g KCl contains
0.477 x 39.1 = 0.25g K
74.56
Thus in 500ml of solution there is 250mg K or 50mg K/100ml.
Diluting 1 in 50 gives a standard of 1mg K/100ml = 10ppm K.
3.1.3 Storage
Store solutions away from direct sunlight in a cool place, ideally at temperatures below 25
o
C. Glass
containers should not be used for storage as they can affect the sodium concentration levels. Standards
should be stored in sealed, plastic vessels and in high concentrations, (e.g. as a stock 1000ppm solution) and
dilutions prepared as required. The long-term storage of low concentration standards is not recommended
due to degradation of ionic species.
DOMINIQUE DUTSCHER SAS
