Automated online measurement of residual corrosion inhibitors in aqueous oil field fluids

A method for determining the concentration of a corrosion inhibitor, comprising:

• receiving an aqueous liquid of a predetermined volume from a fluid stream of an oil field system into an injector of a liquid chromatography system, the aqueous liquid comprising a corrosion inhibitor, the liquid chromatography system in fluid communication with the fluid stream of the oil field system, the liquid chromatography system comprising a stationary phase and a mobile phase, the mobile phase comprising a solvent at a first solvent concentration range and a buffer at first buffer concentration range;
• injecting, by the injector, the aqueous liquid of the predetermined volume and the mobile phase into a column of the liquid chromatography system;
• increasing, by a controller controlling a pump system, the first solvent concentration range to a second solvent concentration range over a first predetermined amount of time, and decreasing, by the controller controlling a pump system, the first buffer concentration range to a second buffer concentration range over the first predetermined amount of time;
• determining, by a detector of the liquid chromatography system, a concentration of corrosion inhibitor in the aqueous liquid flowing out of the column;
• and
• decreasing, by the controller controlling the pump system, the second solvent concentration range to the first solvent concentration range over a second predetermined amount of time, and increasing, by the controller controlling the pump system, the second buffer concentration range to the first buffer concentration range over the second predetermined amount of time.