ASTM D1364 for Water in Volatile Solvents (Karl Fischer Reagent Titration Method)
8. Sampling
8.1 Hygroscopic Solvents, including for example, ketones, acetates, alcohols, and glycol ethers, absorb ambient moisture. It is essential to avoid changes in the water content of these materials during sampling operations. Errors from this source are particularly significant in the analysis of materials having low water content. When analyzing materials that absorb ambient water readily, limit as much as possible contact with air in transferring the specimen into the titration vessel. Avoid intermediate sample containers, if possible.
9. Standardization of Reagent
9.1 Standardize the Karl Fischer reagent each day used by either the color or instrument end point (Section 3) method using the same procedure as used for titrating the sample.
9.1.1 Add to each flask 25 mL of ethylene glycol-pyridene mixture, and titrate this as described in Section 10. Add to the solvent thus titrated, in place of the sample, 0.15 to 0.18 g of water from a weighing bottle or weighing pipet, weighed to the nearest 0.1 mg. Complete titration with Karl Fischer reagent as described in Section 10.
9.1.2 Calculate the equivalency factor, W, of the reagent in terms of water content per millilitre by means of the following equation:
W = A/V
where:
W = equivalency factor, mg of water per mL,
A = weight of water used in the standardization, mg, and
V = volume of Karl Fischer reagent required, mL.
