This method is for determining the amount of fluorocarbon soil-resist agent present on carpet fibers by measurement of elemental fluorine on the pile fiber. This method is useful for measurement of fluorocarbon present on carpet pile fiber as tested within the practical range of 100-1000 µg/g ppm. It may also be used for yarns treated with fluorocarbon anti-soiling agents. 2.Principle 2.1 A weighed fiber specimen is burned in an oxygen combustion flask and the released hydrogen fluoride is absorbed into a sodium hydroxide solution. The fluorine content is measured as dissolved sodium fluoride at a constant pH and ionic strength using a fluoride ion activity electrode and a specific ion meter.