Abstract: The sampling method of the industry standard “Determination of salt content in crude petroleum—Coulometrictitration method”(SY/T 0536—2008) is prone to entrap oil droplets or oil stains in the water alcohol extraction solution under the oil layer, which makes the accuracy and precision of the determination result worse. Theoil contaminationcan be effectively avoided in the water alcohol extraction solutionthrough the sampling methods using a polyethersulfone or polytetrafluoroethylene membrane needle filter, or using a centrifuge tube with an integrated tube cover for layering and using a 12 cm special long needle to insert and puncture the membrane seal at the bottom of the thin tube subsequently.At the same time, the sampling amount is increased by about 5 times, the representativeness of oil sample is improved, and the amount of extraction solution is increased accordingly to facilitate the selection of different detection methods for salt content.

Key words: crude oil, salt content, centrifugal tube, filtration membrane, sampling method