ASTM D4377 Standard Test Method for Water in Crude Oils by Potentiometric Karl Fischer Titration
10. Procedure
10.1 Add the fresh sample solvent to the titration vessel and bring the solvent to end-point conditions as described in 9.2.
10.2 Add the crude to the titration vessel immediately after the mixing step described in 8.1.2.1 using one of the following methods:
10.2.1 Starting with a clean, dry syringe (10 or 5 mL), rinse the syringe two times with the sample and discharge to waste. Withdraw the required amount of sample and discharge any air bubbles. Weigh the syringe to the nearest 0.1 mg. Inject the sample into the titration vessel, clean the needle with a paper tissue, and reweigh the syringe. Titrate the sample until a steady end-point for at least 30 s is reached and record the volume of Karl Fischer reagent to the nearest 0.01 mL (see Note 2 and Note 4).
NOTE 4 - The solvent should be changed when the sample content exceeds 2 g of crude per 15 mL of solvent or when 4 mL of titrant per 15 mL of solvent has been added to the titration vessel.
10.2.2 For viscous crudes, add the sample to a clean, dry dropper bottle and weigh the bottle and crude. Quickly transfer the required amount of sample to the titration vessel with the dropper. Reweigh the bottle. Titrate the sample as in 10.2.1.
NOTE 5 - After adding the sample do not shake the cell.
