111.5.1. Tritium and 14C analysis in alcohol

The presence of tritium and 14C in alcohol in a water sample taken from the oilfield cannot be analysed directly by liquid scintillation counting; it needs to be purified using the distillation process described below.

111.5.2. Equipment and reagents

• Round flask 500 mL, connection size 24/40;

• Fractional distillation Vigreux column 31 cm long, connection size 24/40;

• Dean & Stark collector sized 10 mL;

• Cooling system;

• Heater;

• Magnetic stirrer;

• Liquid scintillation counter with standard 10-20 mL vial;

• Methanol and toluene reagent grade;

• Cocktail Instagel or Ultima Gold.

111.5.3. Procedures

(1) Sample treatment: Add 10% v/v of toluene and extract water by funnel.

(2) Place water sample in standard vial with appropriate cocktail to count 3H and 14C directly on liquid scintillation counter at dual label mode. Calculate tritium (HTO) activity with correction for 14C in methanol contribution.

(3) Add 3 mL of methanol and 1.3 mL of toluene to water sample in the round flask.

(4) Add a magnetic stirring bar to the round flask on the distillation system.

(5) Heat the sample at low power to distil for 5 h.

(6) Collect the distillate (about 4 mL) into the counting vial.

(7) Add cocktail and count by dual label mode with liquid scintillation counter.

(8) Calculate the 14C activity (from 14C-MeOH) using the appropriate correction for HTO influence.