A method and apparatus is provided for determining concentration of components in a liquid hydrocarbon mixture including hydrocarbons and water flowing through an alkylation process. A fluid flow path conveys the liquid continuously from the alkylation process through a first instrument configured for measuring a property of the liquid mixture, and having responsivities to concentration of the components, which are independent of the concentration of the water. A temperature detector generates temperature data for the liquid, and a second instrument measures another property of the liquid mixture. The instruments have mutually distinct responsivities to concentrations of the components. A processor captures data from the temperature detector and instruments, using the data with a model of responsivities of various concentrations of the components at various temperatures, to determine a temperature compensated concentration of the components while the liquid mixture flows continuously through the fluid flow path.