Automated sampling and reaction systems and methods of using the same are provided. The automated sampling and reaction system has a microreactor in fluidic communication with an external sampling valve. The external sampling valve is connected to a priming valve and can be configured to draw sample from a reactor or a reactor stream. The microreactor is connected to a reagent valve and an injection valve. The reagent valve can be configured to draw reagent from a reagent reservoir and discharge reagent to the microreactor to react with sample. The priming valve can be configured to draw wash from a wash reservoir and discharge wash to the external sampling valve to move sample from the external sampling valve to the microreactor. The injection valve is in fluidic communication with a column or detector and discharges the secondary sample into a solvent composition stream.