The molybdenum blue method was prepared according to
the standard method for the examination of water and wastewater
[5]. A 5 N of sulfuric acid was prepared from diluted 35.0 mL of
concentrated H2SO4
(Carlo ERBA, Italy) to 250.0 mL with
de-ionized water. The potassium antimonyl tartrate solution was
prepared by dissolve 0.2743 g of K(SbO)C4H4O6
•1/2H2O (Riedelde
Haen, Germany) in 100.0 mL de-ionized water. The
ammonium molybdate solution was prepared by dissolve 4.0 g of
(NH4
)6Mo7O24•4H2O (Ajax Finechem, Australia) in 100.0 mL
de-ionized water. The ascorbic acid solution was prepared by
dissolve 1.76 g of C6H8O6
(RANKEM, India) in 100.0 mL
de-ionized water. The above solutions were mixed by the ratio of
10:1:3:6 (molybdenum blue solution).