Sodium dihydrogen phosphate salt can be anhydrous, dehydrate or trihydrate depending on the quantity of water it contains. Now, due to the purity and  quantity of water contained by the salt to be used during the preparation of solution. The quantity of salt that will be dissolved to obtain a given concentration will be calculated using the below mathematical formula.

Weight to be taken 

 Where:

  C: Desired Concentration in moles per liter

  Mm: Molecular mass of sodium dihydrogen phosphate salt including water

  V: Desired Volume of the solution in mL

  P:  Purity of the salt to be used

For example: preparation of 1L solution with 50mM sodium  phosphate buffer  by using anhydrous sodium dihydrogen phosphate with 98%.

Weight to be taken will be:

After calculating the mass of salt to be taken

ü  Weight accurately the calculated quantity with both calibrated and verified an analytical balance  

ü  Dissolved the weighted quantity with 500ml of distilled or ultra-pure water and mix so that all salt will be dissolved

ü  Top up to the mark with distilled water or ultrapure water to obtain the desired concentration.

References:

1.      Tracy Paulsen. (2010), Introduction to Chemistry,(pp 124) CK-12 Foundation,

2.      David Harvey,( 2000), Modern Analytical Chemistry,(1^st Ed pp 30-32), USA, McGraw-Hill Campany,

3.      Mac Carthy, P. (1983), A Novel Classification of Concentration Units, (pp 60, 187–189). J. Chem. Educ.

4.      Schwartz, L. M., (1985), Propagation of Significant Figures, (pp 62, 693–697). J. Chem. Educ.