Analisis penentuan Calcium/Magnesium di dalam air dg alat potensiometer (Titrino/Titroprocessor)

Peralatan :
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrode = 6.0504.100 Ca2+ sensitive indicator electrode; input 1
6.0733.100 Ag/AgCl reference electrode (c(KCl) = 3 mol/L)

Pereaksi :
c(Na2EDTA) = 0.05 mol/L in c(KOH) = 0.1 mol/L; D0

Sampel :
100 mL tap water
15 mL c(Acetylacetone) = 0.1 mol/L in c(Trishydroxymethylaminomethane)= 0.1 mol/L (auxiliary complexing agent, pH app. 8.5)

Rangkuman :
Langkah 1 : Ca2+
Langkah 2 : Mg2+·

Perhitungan :

Ca++=EP1*C01*C02/C00;2;mmol/l
Mg++=(EP2-EP1)*C01*C02/C00;2;mmol/l
Total = EP2*C01*C02/C00;2;mmol/l

Ca++ = calcium hardness in mmol/L
Mg++ = magnesium hardness in mmol/L
Total = total hardness in mmol/L
C01 = concentration of titrating agent (0.05 mol/L)
C02 = factor for the conversion mol Þ mmol (1000).

Jawaban :

Ca++=4.245x0.05x1000/100=2.12 mmol/L
Mg++=(5.535-4.245)x0.05x1000/100=0.64 mmol/L
Total = 5.535 x 0.05 x 1000 / 100 = 2.77 mmol/L

EP1=4.245 mL
EP2=5.535 mL
C00=100 mL

· Electrode preparation:Ca electrodes should be conditioned for 10 min. in c(CaCl2) = 0.01mol/L before use.

· The volume of auxiliary reagent can be optimised for the magnesiumcontent. Rule of thumb: Ratio Mg/Acetylacetone app. 0.05.

Literatur :

Metrohm Application Bulletin No. 125: Complexometric simultaneousdetermination of calcium and magnesium in water samples andbeverages with the aid of an ion-selective calcium electrode