A method for calibrating an analysis instrument, e.g., a gas chromatograph, for water analysis that includes four steps. The first step is to continuously remove water from a liquid that contains water to produce a liquid containing a reduced amount of water such as by membrane pervaporation. The second step is to analyze the liquid containing a reduced amount of water for water by a reference water analysis method such as by Karl Fischer titration. The third step is to analyze the stream of liquid containing a reduced amount of water using the instrument to be calibrated, e.g., a gas chromatograph having a helium photoionization pulse discharge detector. The fourth step is to calibrate the instrument using the analysis of the second step. In a related embodiment, a system for normal phase chromatography.